Pharmacological Inhibition of BTK reduces neuroinflammation and stress induced anxiety in vivo

Stress related disorders lead to serious psychiatric disabilities and are comorbid with anxiety and depression. Current therapies targeting several neurotransmitter systems are only able to mitigate symptoms partially. It is well recognized that stress and trauma related disorders lead to a prominent inflammatory response in humans, and in several animal models a robust neuroinflammatory response has been observed. However, the therapeutic potential of targeting specific components of the inflammatory response has not been adequately studied in this context. The current study investigated the NLRP3 - Caspase1-IL-1{beta} pathway, which recent research has identified as a major contributor to exacerbated inflammatory response in several peripheral and central nervous system pathological conditions. Using two different models of stress, first - single prolonged restraint stress followed by brief underwater submersion and second - predator odor exposure in mice, we demonstrate heightened anxious behavior in mice one-week after stress. Females in both models display an exacerbated anxiety response than males within the stressed group. Consistent with this data stressed animals demonstrate upregulation of IL-1{beta}, IL-6, Caspase1 activity and NLRP3 inflammasome activation in brain, with female animals showing a stronger neuroinflammatory phenotype. Pharmacological inhibition of NLRP3 inflammasome activation led to a rescue in terms of anxious behavior as well as attenuated neuroinflammatory response, both of which were significantly more prominent in female animals. Further, we observed induction of activated Brutons Tyrosine Kinase (BTK), an upstream positive regulator of NLRP3 inflammasome activation, in hippocampus and amygdala of stressed mice. Next, we conducted proof-of-concept pharmacological BTK inhibitor studies with Ibrutinib, a drug that is already FDA approved for use in certain types of lymphomas and leukemias, as well as a second inhibitor of BTK, LFM-A13. In both sets of experiments, we found inhibition of BTK significantly reduced the anxious behavior in stressed mice and attenuated the induction of NLRP3 inflammasome, Caspase 1 and IL1{beta}. Our results suggest that BTK inhibition can be further investigated in context of human stress and trauma related disorders as a therapeutic strategy.