PSIX-9 Activation of Multiple Inflammatory Signaling Pathways May Contribute to the Pathogenesis of Idiopathic Cystitis in Felines

Abstract

Abstract Feline idiopathic cystitis (FIC) is a common urinary disorder in domestic cats. Clinical signs include straining or failing to urinate, frequent urination, and discolored urine. Inflammation is a key characteristic in the pathogenesis of cystitis. We assessed circulating inflammatory markers in a retrospective study in cats housed in the Hill’s colony diagnosed with cystitis (n = 4; 15.2 to 18.6yr) and in control cats (n = 8; 5.9 to 16.5 yr). Blood samples were collected at end-of-life immediately before necropsy after they had lived their full lives. End-of-life pathology reports indicated inflammation and presence of inflammatory infiltrates in the bladder with some cats also showing renal inflammation. RNA was extracted from blood collected in PAXgene tubes, and gene expression investigated using NanoString nCounter platform. Analysis was performed using the nSolver software. There was a significant increase in IRAK4, a kinase that activates the NFκB pro-inflammatory signaling pathway, in FIC when compared with controls (1.56, P < 0.05). Small molecule inhibitors of IRAK4 are being developed as targets of inflammation. Signaling molecules in the NFκB pathway were also significantly increased including Rel A (p65 subunit; 1.3 fold), NFκB1 (p100 subunit; 1.3 fold), IKBKB (1.29 fold), and TANK (1.46 fold) in FIC cats (all P < 0.05). Another signaling pathway contributing to pro-inflammatory signaling is the JAK/STAT pathway. There was a significant increase in JAK2 (1.65) and STAT3 (1.48). Blockade of JAK2/STAT3 pathway can attenuate cytokine synthesis and reduce inflammation. STAT6 was also significantly increased in FIC cats (1.35). Activation of STAT6, by IL-4 and IL-13, can lead to systemic inflammation. Activation of the complement immune pathway was also seen in FIC. While the complement system is important for an innate immune response, its sustained activation leads to chronic pathological inflammation. There was a significant increase in complement C1s, an initiator of classical complement activation pathway, in FIC cats (1.43; P < 0.05). A late component, complement C7, was also upregulated in FIC (2.01 fold; P < 0.05). C7 binds to the C5b-6 complex which eventually becomes part of the terminal complement complex. Increased abundance of C7 and eventual terminal complement complex are associated with increased inflammation and may be important in the progression of FIC. There was also an increase in PECAM1 in FIC cats (1.87; P < 0.05). Signaling through PECAM1 leads to the activation of neutrophils and monocytes. DUSP1 was also elevated in FIC (2.24; P < 0.05). Increased abundance of DUSP1 is hypothesized to be a predictor of chronic subclinical inflammation in humans with cardiovascular disease. Our results identify activation of pro-inflammatory signaling pathways that may be potential targets for alleviating inflammation in cystitis. Pathogenesis of FIC is likely multi-factorial, and nutritional intervention to attenuate the activation of inflammatory pathways may be an important strategy in the management of cystitis.