Soluble uric acid induces inflammation via TLR4/NLRP3 pathway in intestinal epithelial cells

Document Type: Original Article

Authors

1 Medical Research Center, the Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, 266000, P. R. China

2 Department of obstctrics, the Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, 266000, P. R. China

3 Shandong Institute of Orthopaedics and Traumatology, the Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, 266000, P. R. China

4 School of Cardiovascular Medicine and Science, King’s College London, BHF Centre, London, SE5 9NU, United Kingdom

Abstract

Objective(s): Hyperuricemia is a risk for cardiovascular and metabolic diseases, but the mechanism is ambiguous. Increased intestinal permeability is correlated with metabolic syndrome risk factors. Intestinal epithelial cells play a pivotal role in maintaining intestinal permeability. Uric acid is directly eliminated into intestinal lumen, however, the mechanism and effect of uric acid on intestinal epithelial cells is poorly explored. Here we carried out an analysis to identify the effect and mechanism of uric acid on intestinal epithelial cells.
Materials and Methods: IEC-6 was exposed to different concentrations of uric acid to simulate the effect of uric acid on intestinal epithelial cells. Cell viability was determined by MTS assay. Protein content and mRNA were assessed using Western blotting and Q-PCR, respectively. Intracellular ROS was determined using flow-cytometry and fluorescence microscopy. Mitochondrial membrane potential was detected by immunofluorescence using a mitochondrial membrane potential assay kit with JC-1. Small interfering RNA transfection was used to suppress the expression of TLR4.
Results: We found soluble uric acid alone increased the release of ROS, depolarized the mitochondrial membrane potential, up-regulated TSPO, increased the expression of TLR4 and NLRP3, and then activated NLRP3 inflammasome and NF-κB signaling, which further resulted in lower expression of tight junction protein and exerted adverse effects on intestinal epithelial cells. Furthermore, the elevated IL-1β could be restored by silencing of TLR4, indicating soluble uric acid induces inflammation via the TLR4/NLRP3 pathway.
Conclusion: Soluble uric acid exerted detrimental effect on intestinal epithelial cells through the TLR4/NLRP3 pathway.

Keywords


1. Abrahamsson TR, Jakobsson HE, Andersson AF, Björkstén B, Engstrand L, Jenmalm MC. Low diversity of the gut microbiota in infants with atopic eczema. J Allergy Clin Immunol.  2012;129:434-440. e432.
2. Acevedo A, Benavides J, Chowdhury M, Lopez M, Pena L, Montenegro A, et al. Hyperuricemia and Cardiovascular Disease in Patients with Hypertension. Conn Med. 2016;80:85-90.
3. Boursi B, Mamtani R, Haynes K, Yang Y-X. The effect of past antibiotic exposure on diabetes risk. Eur J Endocrinol. 2015;172:639-648.
4. Cai W, Duan X-M, Liu Y, Yu J, Tang Y-L, Liu Z-L, et al. Uric acid induces endothelial dysfunction by activating the HMGB1/RAGE signaling pathway. Biomed Res Int. 2017;2017.
5. Caliceti C, Calabria D, Roda A, Cicero AF. Fructose intake, serum uric acid, and cardiometabolic disorders: a critical review. Nutrients. 2017;9:395.
6. Chen Y, Wang L, Pitzer AL, Li X, Li P-L, Zhang Y. Contribution of redox-dependent activation of endothelial Nlrp3 inflammasomes to hyperglycemia-induced endothelial dysfunction. J Mol Med (Berl). 2016;94:1335-1347.
7. Crawshaw AA, Robertson NP. The role of TSPO PET in assessing neuroinflammation. J Neurol. 2017;264:1825-1827.
8. De Nardo D, Latz E. NLRP3 inflammasomes link inflammation and metabolic disease. Trends Immunol. 2011;32:373-379.
9. Gatliff J, East D, Crosby J, Abeti R, Harvey R, Craigen W, et al. TSPO interacts with VDAC1 and triggers a ROS-mediated inhibition of mitochondrial quality control. Autophagy. 2014;10:2279-2296.
10. Henao-Mejia J, Elinav E, Jin C-C, Hao L, Mehal WZ, Strowig T, et al. Inflammasome-mediated dysbiosis regulates progression of NAFLD and obesity. nature. 2012;482:179.
11. Hosomi A, Nakanishi T, Fujita T, Tamai I. Extra-Renal Elimination of Uric Acid via Intestinal Efflux Transporter BCRP/ABCG2. PloS One. 2012;7:e30456.
12. Huang Z, Hong Q, Zhang X, Xiao W, Wang L, Cui S, et al. Aldose reductase mediates endothelial cell dysfunction induced by high uric acid concentrations. Cell Commun Signal. 2017;15:3.
13. Kummer JA, Broekhuizen R, Everett H, Agostini L, Kuijk L, Martinon F, et al. Inflammasome components NALP 1 and 3 show distinct but separate expression profiles in human tissues suggesting a site-specific role in the inflammatory response. J Histochem Cytochem. 2007;55:443-452.
14. Lv Q, Meng X-F, He F-F, Chen S, Su H, Xiong J, et al. High serum uric acid and increased risk of type 2 diabetes: a systemic review and meta-analysis of prospective cohort studies. PloS one. 2013;8:e56864.
15. Mantovani A, Rigolon R, Civettini A, Bolzan B, Morani G, Bonapace S, et al. Hyperuricemia is associated with an increased prevalence of paroxysmal atrial fibrillation in patients with type 2 diabetes referred for clinically indicated 24-h Holter monitoring. J Endocrinol Invest. 2017:1-9.
16. Mårild K, Ye W, Lebwohl B, Green PH, Blaser MJ, Card T, et al. Antibiotic exposure and the development of coeliac disease: a nationwide case–control study. BMC Gastroenterol. 2013;13:109.
17. Okumura R, Takeda K. Roles of intestinal epithelial cells in the maintenance of gut homeostasis. Exp Mol Med. 2017;49:e338.
18. Rizzetto L, Fava F, Tuohy KM, Selmi C. Connecting the immune system, systemic chronic inflammation and the gut microbiome: The role of sex. J Autoimmun. 2018;92:S0896841118301902.
19. Rock KL, Kataoka H, Lai J-J. Uric acid as a danger signal in gout and its comorbidities. Nat Rev Rheumatol. 2013;9:13-23.
20. Sharp FA, Ruane D, Claass B, Creagh E, Harris J, Malyala P, et al. Uptake of particulate vaccine adjuvants by dendritic cells activates the NALP3 inflammasome. Proc Natl Acad Sci USA. 2009;106:870-875.
21. Thaiss CA, Levy M, Grosheva I, Zheng D, Soffer E, Blacher E, et al. Hyperglycemia drives intestinal barrier dysfunction and risk for enteric infection. Science. Mar 23 2018;359:1376-1383.
22. Thevaranjan N, Puchta A, Schulz C, Naidoo A, Szamosi J, Verschoor CP, et al. Age-Associated Microbial Dysbiosis Promotes Intestinal Permeability, Systemic Inflammation, and Macrophage Dysfunction. Cell Host Microbe. 2017;21:455-466.
23. Vandanmagsar B, Youm Y-H, Ravussin A, Galgani JE, Stadler K, Mynatt RL, et al. The NLRP3 inflammasome instigates obesity-induced inflammation and insulin resistance. Nat Med. 2011;17:179-188.
24. Wan X, Xu C, Lin Y, Lu C, Li D, Sang J, et al. Uric acid regulates hepatic steatosis and insulin resistance through the NLRP3 inflammasome-dependent mechanism. J Hepatol. 2016;64:925-932.
25. Xiao J, Zhang X-L, Fu C, Han R, Chen W, Lu Y, et al. Soluble uric acid increases NALP3 inflammasome and interleukin-1β expression in human primary renal proximal tubule epithelial cells through the Toll-like receptor 4-mediated pathway. Int J Mol Med. 2015;35:1347-1354.
26. Xing S-C, Meng D-M, Chen Y, Jiang G, Liu X-S, Li N, et al. Study on the Diversity of Bacteroides and Clostridium in Patients with Primary Gout. Cell Biochem Biophys. 2015;71:707-715.
27. Yadav D, Lee ES, Kim HM, Lee EY, Choi E, Chung CH. Hyperuricemia as a potential determinant of metabolic syndrome. Journal of lifestyle medicine. 2013;3:98.
28. Zhou RB, Yazdi AS, Menu P, Tschopp J. A role for mitochondria in NLRP3 inflammasome activation. Nature. Jan 13 2011;469:221-225.
29. Zhou Y, Fang L, Jiang L, Wen P, Cao H, He W, et al. Uric acid induces renal inflammation via activating tubular NF-κB signaling pathway. PloS one. 2012;7:e39738.
30. Zhu Y, Hu Y, Huang T, Zhang Y, Li Z, Luo C, et al. High uric acid directly inhibits insulin signalling and induces insulin resistance. Biochem Biophys Res Commun. 2014;447:707-714.