Interleukin-4 signaling plays a major role in urogenital schistosomiasis-associated bladder pathogenesis

Abstract

19IL-4 is crucial in many helminth infections, but its role in urogenital schistosomiasis, infection with 20 Schistosoma haematobium worms, remains poorly understood due to a historical lack of animal models. 21The bladder pathology of urogenital schistosomiasis is caused by immune responses to eggs deposited in 22 the bladder wall. A range of pathology occurs, including urothelial hyperplasia and cancer, but 23 associated mechanisms and links to IL-4 are largely unknown. We modeled urogenital schistosomiasis 24 by injecting the bladder walls of IL-4 receptor-alpha knockout(Il4ra -/-) and wild type mice with S. 25 haematobium eggs. Readouts included bladder histology and ex vivo assessments of urothelial 26 proliferation, cell cycle and ploidy status. We also quantified the effects of exogenous IL-4 on urothelial 27 cell proliferation in vitro, including cell cycle status and phosphorylation patterns of major downstream 28 regulators in the IL-4 signaling pathway. There was a significant decrease in the intensity of 29 granulomatous responses to bladder-wall injected S. haematobium eggs in Il4ra -/versus wild type mice. 30 S. haematobium egg injection triggered significant urothelial proliferation, including evidence of 31 urothelial hyperdiploidy and cell cycle skewing in wild type but not Il4ra -/mice. Urothelial exposure to 32 IL-4 in vitro led to cell cycle polarization and increased phosphorylation of AKT. Our results show IL-4 33 signaling is required for key pathogenic features of urogenital schistosomiasis, and that particular 34 aspects of this signaling pathway may exert these effects directly on the urothelium. These findings 35 point to potential mechanisms by which urogenital schistosomiasis promotes bladder carcinogenesis. 36 37 unfortunately sets the stage for the characteristic fibrotic response. For intestinal schistosomiasis, 48 hepatosplenomegaly and portal hypertension may result, or bladder cancer in the case of urogenital 49 schistosomiasis. 50The exact underlying mechanism by which schistosome eggs induce IL-4 production/release is still 51 uncertain [2]. The major sources of IL-4 have also been shown to include other sources beyond the Th2 52 cells themselves [14]. Parasite egg crude extract has been shown to stimulate enormous IL-4 release 53 from basophils [2, 15], mast cells and other non-T-cell, non-B-cell populations [16], which may indeed 54 represent constitutive sources of IL-4, apart from the Th2 cells. Other Fcε receptor negative non-55 lymphocyte sources of IL-4 have also been reported [17, 18]. The most abundant IL-4 inducing egg 56 antigen has since been identified and characterized from S. mansoni and S. haematobium [2, 15, 19, 20]. 57The interleuking-4 inducing principle from Schistosoma eggs (IPSE) binds to IgE on the surface of these 58 non-T-cell sources, inducing massive IL-4 release that subsequently drive type-2 response [2, 15, 19, 59 20]. 60Although the role of IL-4 in driving schistosomiasis-induced pathogenesis is widely studied for hepato-61 splenic schistosomi...

Monocyte and Macrophage-Mediated Pathology and Protective Immunity During Schistosomiasis

“…Polymorphisms in IL-4 and STAT6 promoter gene were associated higher susceptibility to S. haematobium infection in children ( Adedokun et al, 2018 ). Also, IL-4Rα signaling was associated with granuloma formation and bladder pathogenesis after injection of S. haematobium eggs ( Mbanefo et al, 2020 ). Interestingly, 5-lipoxygenase metabolites induce IL-4 and IL-13 that control granuloma size in lung of mice injected with S. mansoni eggs ( Toffoli da Silva et al, 2016 ).…”