American Journal of Physiology-Regulatory, Integrative and Comparative Physiology

Gut microbiome-host interactions play a crucial role in health and disease. Altered gut microbiome composition has been observed in patients with interstitial cystitis/bladder pain syndrome (IC/BPS), a disorder characterized by pelvic pain, voiding dysfunction, and often co-morbid with anxiety/depression. We recently showed that mice deficient for acyloxyacyl hydrolase (AOAH) mimic pelvic pain symptoms and comorbidities of IC/BPS and also exhibit gut dysbiosis. In addition, we previously identified that the conditional knockout (cKO) of two transcriptional regulators of the gene encoding corticotropin-releasing factor, Crf, that are downstream of AOAH, aryl hydrocarbon receptor (AhR) and peroxisome proliferator-activated receptor-{gamma} (PPAR{gamma}), alleviate anxiety/depressive and voiding phenotypes of AOAH-deficient mice. Here, we examined the effects of AhR and PPAR{gamma} in CRF-expressing cells on the dysbiosis of AOAH-deficiency. AOAH-deficient mice with cKO of PPAR{gamma} and AhR/PPAR{gamma} exhibited reduced pelvic allodynia compared to AOAH-deficient mice, suggesting a role for PPAR{gamma} in regulating pelvic pain. 16S rRNA sequencing of fecal stool from female AOAH-deficient mice with a cKO of AhR and/or PPAR{gamma} in CRF-expressing cells identified altered gut microbiota distinct from AOAH-deficient stool. The cKO of AhR and PPAR{gamma} showed improved cecum barrier function in females compared to AOAH-deficient mice, whereas males were primarily affected by PPAR{gamma}, suggesting sex differences in gut responses. Pair-wise comparison of microbiota also suggested sex differences in response to AOAH-deficiency and conditional knockout of AhR and PPAR{gamma}. Our findings suggest that the dysbiosis and leaky gut of AOAH deficiency is mediated by AhR and PPAR{gamma} in CRF-expressing cells and reveal a novel mechanism and therapeutic targets for pelvic pain.

AimUnderlying bioelectrical slow waves are critical for regulating gastric motility, and abnormal spatiotemporal slow-wave dysrhythmias are associated with a range of gastrointestinal disorders. However, the definition and role of the morphology of gastric slow-wave signals have remained limited. This study aimed to investigate the potential of gastric slow-wave morphology as an actionable biomarker. MethodsData were repurposed from a study where, following ethical approval, a control cohort (n=9) and a pathological cohort of patients with chronic unexplained nausea and vomiting (CUNV; n=8) underwent intra-operative high-resolution serosal electrical mapping (96-256 electrodes, 4.0-5.2 mm spacing). Slow waves were identified using validated software, and spatiotemporally averaged waveforms were compared between cohorts. These waveforms were replicated in a computational model of gastric slow-wave propagation to explore potential functional implications. ResultsThe slow-wave morphology of the CUNV cohort exhibited a more gradual recovery stroke compared to controls, which manifested as an increase in the normalized recovery stroke area [0.206 (95% CI: 0.169-0.247) vs. 0.134 (95% CI: 0.106-0.166); p=0.011]. Computational modeling showed that these morphological differences could drive spatial slow-wave dysrhythmias. Considering the evident functional importance of gastric slow-wave morphology, we highlighted the three typical morphological features: 1) rapid, brief upstroke, 2) downstroke, and 3) biphasic recovery stroke. ConclusionAltogether, this study presents a case for gastric slow-wave morphology as a biomarker of gastric health and disease and lays a foundation for the standardization of future slow-wave morphology research. PRACTITIONER POINTSO_LIAbnormal spatial slow-wave propagation is associated with a range of gastrointestinal motility disorders, but morphology has had limited consideration. C_LIO_LISlow-wave morphology differs between cohorts of healthy controls and patients with chronic unexplained nausea and vomiting. C_LIO_LIMultiscale mathematical modeling indicates that a disruption to the slow-wave recovery stroke may contribute to spatial disorganization. C_LI

Regulation of water permeability in the collecting duct is important for osmoregulatory acclimation in teleost fish. In hyperosmotic environments such as seawater (SW), the teleost kidney functions as a site of divalent ion excretion. The collecting ducts reabsorb Na+, Cl-, and water, thereby reducing urine volume and producing small amounts of isotonic urine with high concentrations of divalent ions. In hypoosmotic environments such as freshwater (FW) or low-salinity brackish water (BW), the kidney produces large volumes of hypotonic urine and serves as a site of water excretion; under these conditions, the collecting ducts reabsorb Na+ and Cl- but not water. To identify aquaporins (Aqps) involved in regulating water permeability in the collecting ducts of teleosts, we analyzed renal Aqp expression in a euryhaline marine fish, the Japanese pufferfish (Takifugu rubripes), which possesses 16 Aqp genes in its genome, seven of which (Aqp1aa, 1ab, 3a, 4a, 7, 8bb, and 11a) are expressed in the kidney. Quantitative RT-PCR analysis showed that Aqp1aa and Aqp4a were highly expressed in collecting duct tissues, and that Aqp1aa expression was markedly reduced in fish acclimated to BW. Immunohistochemistry revealed apical localization of Aqp1aa and basolateral localization of Aqp4 in collecting duct cells, with apical Aqp1aa downregulated in BW. These results suggest that Aqp1aa and Aqp4 mediate water reabsorption in SW and that downregulation of Aqp1aa contributes to hypotonic urine production in BW. NEW & NOTEWORTHYRegulation of water permeability in the collecting duct is important for osmoregulation in teleost fish. Expression analyses of aquaporins (Aqps) in the marine pufferfish Takifugu rubripes showed that Aqp1aa and Aqp4a are highly expressed in the collecting duct and localized to the apical and basolateral membranes, respectively. Renal Aqp1aa expression was markedly reduced in fish acclimated to hypoosmotic brackish water. These results indicate that collecting duct water permeability is regulated by Aqp1aa expression.

Clinicians are often forced into the dilemma of whether to battle ocular inflammation or preserve vision imperiled by elevated intraocular pressure (IOP). Anti-inflammatory treatments utilizing glucocorticosteroid regimens may induce glaucoma by chronically elevating IOP via increased trabecular meshwork (TM) resistance to the flow of aqueous humor, but it is not known whether pressure transduction itself is impacted by steroids and how changes in TM mechanosignaling affect conventional outflow resistance and IOP. To address this, we investigated the role of TREK-1 (TWIK-related potassium channel-1), a mechanosensitive K+ channel, in regulation of outflow facility, transmembrane signaling and dexamethasone (DEX)-induced ocular hypertension (OHT). The expression of tandem-pore potassium channels in mouse TM cells was dominated by Trek-1 (Kcnk2) mRNA, with residual expression of Traak, Tresk2 and Twik3 and vanishingly low levels of Task1 and Trek2. DEX suppressed Trek1 transcription by [~]80% but did not affect expression of Trpv4 and Piezo1 genes. Chronic DEX administration depolarized the membrane potential of TM cells and elevated IOP in mice whereas the selective TREK-1 agonist ML-402 lowered IOP in rodent OHT models. ML-402 doubled the outflow facility in perfused mouse eyes at all applied pressures and hyperpolarized DEX-treated TM cells. These in vitro, ex vivo and in vivo results implicate TREK-1 channels in homeostatic regulation of TM mechanosignaling, conventional outflow regulation and IOP homeostasis. Suppression of TREK-1 signaling by corticosteroids underlies OHT and could contribute to steroid glaucoma but this can be obviated by pharmacological stimulation of the channel with cornea-permeant ML-402 eye drops.

Estrogen plays a central role in regulating the vaginal environment, but the specific contribution of epithelial estrogen receptor (ESR1) to microbial and biochemical homeostasis has not been fully defined. In our previous work, we showed that epithelial ESR1 is indispensable for estrogen-induced epithelial proliferation, cornification, and MUC1 expression. Here, using mice with conditional deletion of Esr1 in vaginal epithelial cells, called epithelial Esr1d/d, we extend these findings to demonstrate that epithelial ESR1 also regulates glycogen deposition, luminal pH, and microbial stability. Compared to control littermates, epithelial Esr1d/d mice reduced glycogen abundance, elevated vaginal pH, and a compositional shift in the vaginal microbiome, marked by enrichment of Comamonadaceae and loss of Lactobacillus species, without significant differences in alpha diversity. These changes parallel features of postmenopausal dysbiosis in women. Together, our findings identify epithelial ESR1 as a master regulator of multiple pathways that sustain vaginal homeostasis, integrating epithelial metabolism, barrier function, and host-microbe interactions. This work provides a mechanistic framework to understand postmenopausal vaginal dysbiosis and suggests epithelial estrogen signaling as a potential therapeutic target for genitourinary syndrome of menopause. Significance StatementThe vaginal environment is essential for reproductive and gynecologic health, yet the mechanisms by which estrogen shapes this niche remain incompletely understood. We show that epithelial estrogen receptor (ESR1) regulates glycogen deposition, luminal pH, and microbial composition in the murine vagina. Loss of epithelial ESR1 reduced glycogen and increased luminal pH without altering overall microbial diversity, but shifted community structure toward enrichment of Comamonadaceae, a family associated with neutral to mildly alkaline environments. These findings identify epithelial ESR1 as a key regulator of the metabolic and physicochemical conditions that maintain vaginal microbial balance and provide a mechanistic framework for understanding postmenopausal dysbiosis.

The composition and volume of tear fluid lining the ocular surface are governed by the rates of lacrimal gland secretion, tear film evaporation, nasolacrimal drainage, and epithelial ion and water transport. Tear fluid hyperosmolality and reduced volume are key drivers of dry eye disease (DED) pathogenesis. We constructed a mathematical model to compute the composition and volume of tear fluid and epithelial cell compartments, with transport parameters specified for the mouse eye from published data and in vivo measurements of ocular surface potential differences. The model accounted for transcellular and paracellular transport across the epithelia under open-circuit conditions utilizing flux equations for individual transport mechanisms, with mass balance constraints on solute and water content in cytoplasm and tear fluid. Under DED conditions established by reduced lacrimal secretion and increased evaporation, the model predicted the efficacy of currently available DED therapies including punctal plugs, humidification goggles, lacrimal gland stimulation, and artificial tears eye drops. The model also predicted the limited efficacy of anti-absorptive and pro-secretory drugs targeting epithelial ion transporters, and the high efficacy of targeting epithelial water permeability or paracellular ion permeability. The modeling herein provided quantitative predictions to prioritize novel targets for DED and drive the development of new therapies. Author SummaryDry eye disease (DED) affects billions of adults worldwide, but a full picture is lacking of how the tear film becomes abnormally thin and hyperosmolar. The computer model built here links four processes - tear production by the lacrimal gland, tear fluid evaporation, tear drainage through tear ducts, and transport of solutes and water across eye surface epithelial cells - to predict the thickness and composition of the tear film in various conditions. Model parameters were selected using published data and electrical measurements of voltage changes across the ocular surface produced by ion transport. The model predicted that existing therapies, such as punctal plugs, moisture goggles, or stimulating tear production, can substantially increase tear thickness or lower saltiness. The model also predicted limited efficacy of drug therapies in current development that target ion transport, and identified epithelial cell water transport and paracellular ion permeability as novel targets for DED treatment. By making ocular surface transport mechanisms explicit and testable, our work offers a roadmap for development of new therapies that restore a healthy tear film, a major unmet medical need.

Cystathionine {gamma}-lyase (CSE) produces hydrogen sulfide (H2S), a vasodilator critical for vascular function. While its systemic effects are well-documented, its role in erectile physiology remains unclear. This study investigated the impact of CSE deletion on vascular and erectile tissue reactivity. We hypothesized that CSE knockout (CSE-KO) mice would exhibit endothelial dysfunction. A total of 22 CSE-KO and 22 age-matched wild-type (WT) controls were studied at one year of age. The internal iliac artery (IIA), internal pudendal artery (IPA), and corpus cavernosum (CC) were harvested for ex vivo functional assessments using tissue, wire, and pressure myography. Vasoconstriction was evaluated using phenylephrine, endothelin-1, U-46619, and electrical field stimulation (EFS). Endothelium-dependent relaxation was assessed using acetylcholine (ACh) and flow-mediated dilation, while endothelium-independent relaxation was evaluated using sodium nitroprusside (SNP). Sodium sulfide (Na2S) was used to assess H2S-mediated dilation. Non-adrenergic, non-cholinergic (NANC) transmission was evaluated using EFS. No significant differences were observed in ACh-, SNP-, or flow-mediated relaxation, although CSE-KO mice demonstrated impaired NANC-nerve mediated relaxation in the CC. Moreover, CSE-KO mice exhibited significantly enhanced CC contraction in response to U-46619 and EFS, suggesting increased vascular resistance in the end organ CC rather than the pre-penile arteries. Histological analysis revealed no significant structural or fibrotic remodeling in any tissue, although there was a trend toward increased collagen deposition in the IIA and IPA. These findings indicate that chronic CSE deficiency does not impair endothelial function but alters neurogenic control and increases vasoconstrictive sensitivity specifically in the CC, potentially predisposing to erectile dysfunction. NEW & NOTEWORTHYThis study highlights the critical role of hydrogen sulfide (H2S) in erectile physiology by demonstrating that CSE deletion does not impair endothelial function but significantly enhances neurogenic and thromboxane A2 receptor-induced vasoconstriction specifically in the corpus cavernosum (CC). These findings suggest that endogenous H2S modulates neurovascular control of erection. Its deficiency predisposes the erectile system to heightened vascular resistance predominantly in the end organ, providing novel insights into the vascular mechanisms underlying erectile dysfunction.

The central nervous system modulates heart function on a beat-to-beat basis via increasingly understood mechanisms. Conversely, whether and how humoral/functional cardiac variations shape brain activity and adaptive behavior remains unclear. This study shows that mice overexpressing adenylyl cyclase type 8 in myocytes (TGAC8), characterized by persistently elevated heart rate/contractility, also display increased locomotion. This effect is sustained by enhanced gamma rhythms, as evidenced by simultaneous behavioral and EEG/ECG monitoring. These changes are specific because they are not paralleled by other modifications, such as heightened anxiety-like behavior. In unison, TGAC8 mice hippocampus exhibits upregulated GABA-A receptors, whose activation chiefly accounts for gamma activity generation. Moreover, the Granger causality analysis between ECG and EEG attests to the causal involvement of the autonomic component of the heartbeat in shaping EEG gamma oscillations in a bottom-up modality. Mechanistically, TGAC8 harbors elevated circulating dopamine/DOPA levels of cardiac origin and upregulated hippocampal D5 dopamine receptor levels. In synergy with the GABA-A receptor, D5 activation favors hippocampal inhibitory currents that drive EEG gamma oscillations. These studies, therefore, inform how heart-initiated functional and/or humoral modifications reverberate back to the brain to modulate specific primary adaptive responses, such as locomotion. SignificanceThe brain is continuously aware of the functional status of many bodily organs, modulating, for instance, the hearts activity beat-by-beat. Conversely, how cardiac activity modifications impact brain function and behavior is less understood. We disclose that augmenting myocyte adenyl cyclase 8 (AC8) activity in mice increases their locomotion. Elevated cardiac AC8 levels lead to higher circulating dopamine and DOPA, hormones crucially involved in movement control, and increased expression of the hippocampuss GABA-A and D5 receptors; the activation of the latter modifies hippocampal gamma oscillations shaping locomotor activity. Thus, the brain interprets changes in myocardial AC8 activity as a "sustained exercise-like" situation and responds by activating areas commanding to increase locomotion.

Recent studies have emphasized the importance of the nitric oxide synthase (NOS)-independent, nitrate (NO3-) [->] nitrite (NO2-) [->] nitric oxide (NO) pathway in skeletal muscle. In particular, it has been hypothesized that this pathway is especially active in type II, or fast-twitch, muscle fibers, necessitating greater NO3- and NO2- storage. We therefore measured NO3- and NO2- concentrations in the predominantly fast-twitch vastus lateralis and predominantly slow-twitch soleus muscles of rats. Contrary to the above hypothesis, we found that NO3- and NO2- concentrations were 3.4-fold and 1.8-fold higher, respectively, in the soleus. On the other hand, NO signaling (i.e., cyclic guanosine monophosphate (cGMP) level) was comparable in the two muscles. Although the physiological significance of these observations remains to be determined, we speculate that NO production via the NO3- [->] NO2- [->] NO pathway is normally higher in slow-twitch muscles, thus helping compensate for their inherently lower NOS activity.

The gonadotrophin-releasing hormone (GnRH) pulse generator is a critical neural oscillator that governs reproductive function through the pulsatile release of luteinising hormone (LH) and follicle stimulating hormone (FSH). Early electrophysiological studies, notably by Ernst Knobil, identified multiunit activity (MUA) volleys in the mediobasal hypothalamus that aligned with LH pulses, suggesting a neural basis for GnRH pulsatility. Although GnRH neurons exhibit some intrinsic secretory rhythmicity in vitro, their isolated electrophysiological signatures have proven inconsistent. Recent advances, including GCaMP fibre photometry in freely behaving mice, have revealed a precise correlation between episodic GnRH distal processes and LH pulses. However, it is now well established that a neural oscillator comprising hypothalamic kisspeptin neurones co-expressing neurokinin B and dynorphin, collectively termed the KNDy network, represents the core construct of the GnRH pulse generator. Understanding the dynamics of this network and its modulation by external inputs such as stress, metabolic cues, and circadian rhythms is essential. Computational modelling provides a systematic framework for integrating experimental data with mechanistic and predictive analyses to decode the GnRH pulse generator dynamics.

The kidney regulates extracellular fluid and electrolyte homeostasis. Its function is modulated by the renin-angiotensin-aldosterone system (RAAS). Overactivation of the RAAS, such as in chronic Ang II infusion, promotes vasoconstriction, anti-natriuresis, and hypertension. Kidney function is also modulated by circadian clocks. Indeed, glomerular filtration rate, filtered electrolyte loads, urine volume, and urinary excretion all exhibit notable diurnal rhythms, which reflect, in part, the regulation of renal transporter proteins by circadian clock genes. Key renal transporters that are regulated by clock gene proteins include sodium-hydrogen exchanger 3 (NHE3), sodium-glucose cotransporter 1 (SGLT1), Na+-K+-2Cl- cotransporter (NKCC2), Na+-Cl- cotransporter (NCC), and epithelial sodium channel (ENaC), which are targeted by diuretics used to treat hypertension. The objective of the present study was to assess the effect of administration time on the natriuretic and diuretic effects of loop, thiazide, and K+-sparing diuretics, which are common treatments for hypertension, and how those effects differ between a normotensive and hypertensive kidney. Loop diuretics inhibit NKCC2 on the apical membrane of the thick ascending limb; notably, In Ang II-induced hypertension, NKCC2 is differentially regulated along the medullary versus cortical thick ascending limb. Thiazide diuretics inhibit NCC on the distal convoluted tubule, and K+-sparing diuretics inhibit ENaC on the connecting tubule and collecting duct. We simulated Na+ transporter inhibition using computational models of kidney function at different times of day. The simulation results predicted qualitatively similar diurnal oscillations in segmental transport in the normotensive and hypertensive kidneys, and highlighted significant time-of-day differences in the natriuresis, diuresis, and kaliuresis responses. NEW & NOTEWORTHYChronic infusion of angiotensin II promotes vasoconstriction, salt retention, and hypertension. Blood pressure and kidney function exhibit circadian rhythms. Given the diurnal variations in the expression levels of key renal electrolyte transporters, how do the natriuretic and diuretic effects of diuretics, a common treatment for hypertension that targets renal transporters, vary during the day? To answer this question, we simulated Na+ transporter inhibition using computational models of kidney function at different times of day.

Proteins from brain cells, including Glial fibrillary acidic protein (GFAP), has been tested for diagnostic and prognostic of neurological dysfunctions. Release of GFAP into the blood-stream, may be a consequence of its up-regulation in reactive astrocytes. However, astrocytic-GFAP expression is also increased during brain remodeling after physiological perturbations such as osmotic challenge. The presence and quantification of GFAP in blood circulation have never been investigated in the context of brain responses to environmental variations in wildlife. In a wild amphibian (green frogs, Pelophylax sp.), captured in several ponds with different salinity, GFAP was detected in plasma. Males from more saline ponds exhibited higher plasmatic GFAP levels, independent to their blood osmolality, suggesting that plasmatic GFAP-level reflects cerebral response to osmotic challenge. Plasmatic-GFAP correlated with immune markers (hemoglobin binding proteins, lymphocytes, neutrophils and monocytes), size and body condition, reinforcing its role as a physiological biomarker. We also highlighted that captivity had a significant effect on plasmatic-GFAP levels with sex-specific dynamics, masking the response to a short-term experimental salinity exposure. For the very first time, we show that plasmatic-GFAP levels could be a biomarker of brain plasticity to environmental conditions, physiological traits, and stress responses in wildlife. Significant StatementWe investigated the use of brain Glial fibrillary acidic protein (GFAP), a cytoskeletal protein of astrocytes, that has been associated with brain disorders in clinical studies, as a biomarker of environmental conditions and individual traits in wildlife. In a wild amphibian, plasmatic GFAP-levels were correlated with the salinity of ponds, immune markers and size for males. GFAP-levels were correlated with body condition for both sexes. Interestingly, captivity induced transient increase of plasmatic-GFAP levels, probably due to stress. In our study, we demonstrate that plasmatic-GFAP levels may represent an excellent brain biomarker of its plasticity to environmental conditions, physiological traits, and stress responses in wildlife.

"Dry eye", characterized by symptoms of ocular discomfort and visual disturbances due to decreased tear secretion, affects 16 million Americans. Yet, there is currently no cure for dry eye as the mechanistic details of water secretion in the tear-producing lacrimal gland have not been fully elucidated. While a transcellular water secretion pathway via water channels like AQP5 has been reported, the existence and function of a paracellular pathway via tight junctions between epithelial cells remains controversial. The actomyosin cytoskeleton localizes to the apical junctions of epithelial cells across organs and regulates tight junction integrity. Here, we report that non-muscle myosin IIC (NMIIC) is enriched at apical junctions of ductal epithelial cells in the lacrimal gland, leading us to hypothesize that NMIIC regulates tear secretion through modulation of tight junction permeability. Consistent with this hypothesis, we found that tear volume after carbachol stimulation was significantly increased in mice lacking NMIIC, and levels of the tight junction protein ZO-1 were significantly reduced. Furthermore, pharmacological activation of NMIIC by 4-Hydroxyacetophenone in wildtype mice significantly inhibited tear secretion. In summary, our findings reveal a paracellular water secretion pathway in the lacrimal gland, which is regulated by NMIIC-mediated modulation of ductal cell tight junctional permeability, and can be targeted by small molecules. Significance StatementWhile dry eye affects more than 16 million Americans, there is currently no cure as the mechanisms underlying tear secretion are incompletely understood. Here, we report first evidence for the existence and function of a paracellular water pathway, in which water flows between cells, in the lacrimal gland. We also show that this pathway is directly regulated by the modulation of tight junction permeability by non-muscle myosin IIC (NMIIC). This study thus identifies a new mechanism for exocrine secretion, which can be targeted towards developing treatments for dry eye/mouth syndrome.

Increased red cell distribution width (RDW), which measures erythrocyte size variability (anisocytosis), has been linked to early mortality in many diseases and normal aged population through unknown mechanisms. Hypoxia has been proposed to increase both RDW and mortality. However, experimental evidence, especially in animal models, is lacking. Here, we show that chronic hypobaric hypoxia (~10% O2) increases erythrocyte numbers, hemoglobin and RDW, while reducing longevity in male mice. Compound heterozygous knockout (chKO) mutations in succinate dehydrogenase (Sdh; mitochondrial complex II) genes Sdhb, Sdhc and Sdhd reduce high RDW and immature reticulocyte fraction, and increase healthy lifespan in chronic hypoxia. Hemoglobin and erythrocyte numbers in hypoxia do not show statistically significant differences between Sdh chKO and WT mice. These results identify a mitochondrial mechanism regulating both RDW and organismal adaptation to chronic hypoxia, and suggest SDH as a potential therapeutic target to reduce high RDW-associated clinical mortality.

The goal of the present study was to investigate the functional implications of sex and species differences in the pattern of transporters along nephrons in the rat and mouse kidney, as reported by Veiras et al. (J Am Soc Nephrol 28: 3504-3517, 2017). To do so, we developed the first sex-specific computational models of epithelial water and solute transport along the nephrons from male and female mouse kidneys, and conducted simulations along with our published rat models. These models account for the sex differences in the abundance of apical and basolateral transporters, glomerular filtration rate, and tubular dimensions. Model simulations predict that 73% and 57% of filtered Na+ is reabsorbed by the proximal tubules of male and female rat kidneys, respectively. Due to their smaller transport area and lower NHE3 activity, the proximal tubules in the mouse kidney reabsorb a significantly smaller fraction of the filtered Na+, at 53% in male and only 34% in female. The lower proximal fractional Na+ reabsorption in female kidneys of both rat and mouse is due primarily to their smaller transport area, lower Na+/H+ exchanger activity, and lower claudin-2 abundance, culminating in significantly larger fractional delivery of water and Na+ to the downstream nephron segments in female kidneys. Conversely, the female distal nephron exhibits a higher abundance of key Na+ transporters, including Na+-Cl- cotransporters in both species, epithelial Na+ channels for the female rat, and Na+-K+-Cl-cotransporters for the female mouse. The higher abundance of transporters accounts for the enhanced water and Na+ transport along the female rat and mouse distal nephrons, relative to the respective male, resulting in similar urine excretion between the sexes. Model simulations indicate that the sex and species differences in renal transporter patterns may partially explain the experimental observation that, in response to a saline load, the diuretic and natriuretic responses were more rapid in female rats than males, but no significant sex difference was found in mice. These computational models can serve as a valuable tool for analyzing findings from experimental studies conducted in rats and mice, especially those involving genetic modifications.

Chronic angiotensin II (AngII) infusion is an experimental model that induces hypertension in rodents. The natriuresis, diuresis, and blood pressure responses differ between males and females, perhaps unexpectedly, given the rodent kidney, which plays a key role in blood pressure regulation, exhibit marked sex differences. Those sex differences include morphology, hemodynamics, and, under healthy (undrugged) conditions, solute and electrolyte transporter abundance. Notably, compared to the male rat nephron, the female rat nephron exhibits lower Na+/H+ exchanger 3 (NHE3) activity along the proximal tubule, but higher Na+ transporter activities along the distal segments. AngII infusion-induced hypertension induces a pressure natriuretic response that reduces NHE3 activity and shifts Na+ transport capacity downstream, to different extents in the two sexes. The goals of this study are (i) to understand how the sexually dimorphic responses differentially impact segmental electrolyte transport following a 14- day AngII infusion, and (ii) to identify and explain any sex differences in the effects of loop diuretics, thiazide diuretics, and K+-sparing diuretics. To achieve those goals, we developed sex-specific computational models of renal epithelial transport of electrolytes and water. Model simulations suggest that the NHE3 downregulation in the proximal tubule is a major contributor to natriuresis and diuresis in hypertension, with a stronger effect in males. Due to the downstream shift of Na+ transport load in hypertension, all three diuretic classes are predicted to induce stronger natriuretic and diuretic effects under hypertension compared to normotension, especially in females. New and NoteworthySex differences in the prevalence of hypertension are found in humans and animal models. The kidney, which plays an important role in blood pressure regulation, exhibits sex differences in morphology, hemodynamics, and membrane transporter distributions. This computational modeling study provides insights into how the sexually dimorphic responses to a 14-day angiotensin II infusion differentially impact segmental electrolyte transport. Simulations results also explain sex differences in the effects of loop diuretics, thiazide diuretics, and K+-sparing diuretics.

Throughout pregnancy, the kidneys undergo significant adaptations in morphology, hemodynamics, and transport to achieve the volume and electrolyte retention required to support a healthy pregnancy. Additionally, during pregnancies complicated by chronic hypertension, altered renal function from normal pregnancy occurs. The goal of this study is to analyze how inhibition of critical transporters affects gestational kidney function as well as how renal function is affected during chronic hypertension in pregnancy. To do this, we developed epithelial cell-based multi-nephron computational models of solute and water transport in the kidneys of a female rat in mid- and late pregnancy. We simulated the effects of key individual pregnancy-induced changes on renal Na+ and K+ transport: proximal tubule length, Na+/H+ exchanger isoform 3 (NHE3) activity, epithelial Na+ channel activity (ENaC), K+ secretory channel expression, and H+-K+-ATPase activity. Additionally, we conducted simulations to predict the effects of inhibition and knockout of the ENaC and H+-K+-ATPase transporters on virgin and pregnant rat kidneys. Our simulation results predicted that the ENaC and H+-K+-ATPase transporters are essential for sufficient Na+ and K+ reabsorption during pregnancy. Last, we developed models to capture changes made during hypertension in female rats and considered what may occur when a rat with chronic hypertension becomes pregnant. Model simulations predicted that in hypertension for a pregnant rat there is a similar shift in Na+ transport from the proximal tubules to the distal tubules as in a virgin rat.

1.Introduction: Inflammatory bowel disease (IBD) involves aberrant immune responses and is associated with both cardiovascular disease risk and altered intestinal blood flow. However, little is known about how IBD affects regulation of perivascular nerves that mediate blood flow. Previous work found perivascular nerve function is impaired in mesenteric arteries with IBD. The purpose of this study was to determine the mechanism of impaired perivascular nerve function. Methods: RNA sequencing was performed on mesenteric arteries from IL10-/- mice treated with H.hepaticus to induce disease (IBD) or left non-gavaged (Control). For all other studies, Control and IBD mice received either saline or clodronate liposome injections to study the effect of macrophage depletion. Perivascular nerve function was assessed using pressure myography and electrical field stimulation. Leukocyte populations, and perivascular nerves, and adventitial neurotransmitter receptors were labeled using fluorescent immunolabeling. Results: IBD was associated with increased in macrophage-associated gene expression, and immunolabeling showed accumulation of adventitial macrophages. Clodronate liposome injection eliminated adventitial macrophages, which reversed significant attenuation of sensory vasodilation, sympathetic vasoconstriction and sensory inhibition of sympathetic constriction in IBD. Acetylcholine-mediated dilation was impaired in IBD and restored after macrophage depletion, but sensory dilation remained nitric oxide independent regardless of disease and/or macrophage presence. Conclusion: Altered neuro-immune signaling between macrophages and perivascular nerves in the arterial adventitia contributes to impaired vasodilation, particularly via dilatory sensory nerves. Targeting the adventitial macrophage population may help preserve intestinal blood flow in IBD patients.

Hypoxia (low oxygen availability) is a common environmental stressor in estuarine ecosystems that negatively affects fish survival as well as physiological and behavioral responses. However, the effects of hypoxia on the brain remains poorly understood, particularly in non-model species. Here, we investigated how prolonged hypoxia influences neural, vascular, and molecular responses in the brain of the speckled sanddab (Citharichthys stigmaeus), an ecologically relevant estuarine flatfish. Fish were exposed to normoxic or hypoxic conditions for seven days, and responses were assessed using histological analyses of neural proliferation and vascular structure, alongside transcriptomic and proteomic profiling. Hypoxia increased neural cell proliferation and progenitor activation in the hypothalamic nucleus recessus lateralis (NRL) and optic tectum, while reducing survival of newly generated cells. At the tissue level, hypoxia induced region-specific vascular remodeling, characterized by increased vessel area and vessel number without evidence of widespread endothelial proliferation. At the molecular level, transcriptomic and proteomic analyses revealed consistent enrichment of biological processes related to stress responses, development, metabolism, and cellular homeostasis, despite limited overlap between individual genes and proteins. Gene- and protein-level analyses further indicated activation of hypoxia-responsive pathways, including HIF signaling and oxidative stress protection, alongside selective metabolic reprogramming. Together, these findings demonstrate that hypoxia induces multi-level changes in the brain, linking neural plasticity, vascular remodeling, and molecular responses. This integrated response likely supports brain function under reduced oxygen availability in dynamic estuarine environments and highlights the role of the brain in regulating responses to environmental stress.

Alpacas (Vicugna pacos) are reported to be the rare mammal in which the penis enters the uterus in mating. To date, however, only circumstantial evidence supports this assertion. Using female alpacas culled for meat, we determined that the alpaca penis penetrates to the very tips of the uterine horns, abrading the tract and breaking fine blood vessels. All female alpacas sacrificed one hour or 24 hours after mating showed conspicuous bleeding in the epithelium of some region of their reproductive tract, including the hymen, cervix and the tips of each uterine horn, but typically not in the vagina. Unmated females showed no evidence of conspicuous bleeding. Histological examination of mated females revealed widespread abrasion of the cervical and endometrial epithelium, injuries absent in unmated females. Within one hour of mating, sperm were already present in the oviduct. The male alpacas cartilaginous penis tip with a hardened urethral process is likely responsible for the copulatory abrasion. The entire female reproductive tract interacts with the penis, functioning like a vagina. Alpacas are induced ovulators, and wounding may hasten delivery of the seminal ovulation-inducing factor beta-NGF into the females blood stream. There is no evidence of sexual conflict in copulation in alpaca, and thus wounding may also be one of a variety of mechanisms devised by mammals to induce a beneficial, short-term inflammatory response that stimulates blastocyst implantation, the uterine remodeling associated with placental development, and thus the success of early pregnancy.