Abstract: TH-PO369

Palmitate Aggravates Proteinuria-Induced Cell Apoptosis and Inflammation via CD36-NLRP3-Caspase-1 Axis in the Proximal Tubular Cells of Obese Mice

Session Information

Category: Cell Biology

  • 201 Cell Signaling, Oxidative Stress

Authors

  • Li, Lung-Chih, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung city, Taiwan
  • Yang, Jenq-Lin, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung city, Taiwan
  • Lee, Wen-Chin, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung city, Taiwan
  • Lee, Chien-Te, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung city, Taiwan
  • Chen, J. B., Kaohsiung Chang Gung Memorial Hospital, Kaohsiung city, Taiwan
  • Ruan, Xiong Z., University College London (UCL) Medical School, London, United Kingdom
  • Chen, Wei-Yu, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung city, Taiwan
Background

Dyslipidemia is common in obesity and elevated free fatty acid (FFA) is prominent in these patients. Palmitate, a long-chain saturated FA, accounts for the majority of FFA and causes renal injury in obesity. CD36 is a class B scavenger with widespread tissue distribution, including renal proximal tubular cells. The NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome is a multi-protein complex, which contains NLRP3, apoptosis-associated speck-like protein containing a CARD (caspase recruitment domain)(ASC), and caspase-1, that forms upon exposure to pathogens or danger signals to activate IL-1β and IL-18 secretion and lead to cell death. Our aims are to investigate whether CD36 and NLRP3 inflammasome contribute to FFA-induced inflammation and cell death in obesity-related tubulopathy.

Methods

High fat diet (HFD)-fed C57BL/6 mice and palmitate-treated renal tubular cells were used as in vivo and in vitro models in the current study. Sulfo-N-succinimidyl oleate (SSO) was used to treat mice and cells as a CD36 inhibitor. Stable knockdown of caspase-1 using shRNA were developed in HK2 cells (a proximal tubular cell line). The protein expressions of IL-1β, IL-18, and NLRP3 were assessed by immunohistochemistry in the renal tissues and western blotting in the cells. The expression and colocalization of NLRP3 and ASC were examined by immunofluorescent staining. The cell death and apoptosis of HK2 cells were checked by cell viability assay and TUNEL staining, respectivelly.

Results

The expressions of CD36, IL-1β, and IL-18 were increased progressively in the kidney of HFD-fed mice. SSO attenuated HFD-induced upregulation of IL-1β, IL-18 and NLRP3 and also decreased the colocalization of NLRP3 and ASC in the proximal tubular cells of mouse kidney. In HK2 cells, palmitate induced the maturation of IL-1β, IL-18 and caspase-1 in a dose-dependent manner, while SSO ameliorated it. SSO also abolished palmitate-induced cell death and apoptosis in a dose-dependent manner. Furthermore, knockdown of caspase-1 abrogated palmitate-induced cell death and apoptosis in HK2 cells.

Conclusion

FFA causes renal tubular cells inflammation and cell death/apoptosis via CD36-NLRP3-caspase-1 axis, which may explain, at least partly, the mechanism of obesity-related nephropathy.

Funding

  • Government Support - Non-U.S.