Aims: We examined that (a) how the endotoxic stress affects peroxisomal function and autophagic degradation of peroxisomes-pexophagy, (b) how a superimposed dysfunction of lysosomes and pexophagy modifies responses to lipopolysaccharide (LPS), and (c) the mechanisms of peroxisomal contribution to renal injury. To accomplish this, we used lysosome-defective Lyst-mice in vivo and primary endothelial cells in vitro, and compared the responses with wild-type (WT) littermates.
Results: LPS induced pexophagic degradation, followed by proliferation of peroxisomes in WT mice, which was abolished in Lyst-mice. Lyst-mice exhibited impaired activation of catalase, which together with preserved hydrogen peroxide-generating β-oxidation resulted in redox disequilibrium. LPS treatment induced a heightened inflammatory response, increased oxidative damage, and aggravated renal injury in Lyst-mice. Similarly, as in vivo, LPS-activated lysosomal (LYS) pexophagy and transiently repressed peroxisomes in vitro, supported by reduced peroxisomal density in the vicinity of lysosomes. Peroxisomal dynamics was also abolished in lysosome-defective cells, which accumulated peroxisomes with compromised functions and intraorganellar redox imbalance.
Innovation: We demonstrated that pexophagy is a default response to endotoxic injury. However, when LYS dysfunction (a frequent companion of chronic diseases) is superimposed, recycling and functioning of peroxisomes are impaired, and an imbalance between hydrogen peroxide-generating β-oxidation and hydrogen peroxide-detoxifying catalase ensues, which ultimately results in peroxisomal burnout.
Conclusion: Our data strongly suggest that pexophagy, a cellular mechanism per se, is essential in functional maintenance of peroxisomes during LPS exposure. Inhibition of pexophagy results in accumulation of impaired peroxisomes, redox disequilibrium, and aggravated renal damage.