Contribution of NLRP3 Inflammasome Activation to Glomerular Injury during Hyperhomocysteinemia with and without Enhanced Exosome Secretion

Abstract

Hyperhomocysteinemia (hHcy) has been demonstrated to activate NLRP3 inflammasome leading to podocyte injury and glomerular sclerosis. However, it remains unknown whether exosome‐mediated secretion of NLRP3 inflammasome products is involved in the development of glomerular injury during hHcy. In the present study, we examined the possible role of increased exosome secretion during NLRP3 activation in the inflammatory response and tested whether without robust release of exosomes, inflammatory response and glomerular injury still occur. Exosome biogenesis inhibitor‐GW4869, lysosome trafficking stimulator‐rapamycin or ASM inhibitor‐amitriptyline were used in mice to answer this question. By nanoparticle tracking analysis, it was found that hHcy significantly increased urinary exosome release in WT/WT mice. In Smpd1trg/Podocre (podocyte‐specific ASM transgenic) mice, this hHcy‐induced increase in urinary exosomes was significantly enhanced. Pretreatments of WT/WT mice and Smpd1trg/Podocre mice with amitriptyline (Ami), GW4869 (GW) and rapamycin (Rap) all prevented increases in urinary exosomes during hHcy. In podocytes isolated from WT/WT mice and Smpd1trg/Podocre mice, similar results were obtained when we measured exosomes released from these cells after different treatments. Confocal microscopy demonstrated that Ami not only prevented hHcy‐induced NLRP3 inflammasome formation and activation in glomeruli, but also decreased exosome release in podocytes of WT/WT mice and Smpd1trg/Podocre mice. However, GW and Rap only blocked exosome‐mediated IL‐1β secretion from podocytes, but had no effect on inflammasome formation or activation in glomeruli during hHcy. However, all 3 treatments attenuated the inflammatory response in glomeruli and associated injury as shown by reduced immune cell aggregation, decreased proteinuria and ameliorated glomerular sclerosis. These results suggest that without enhanced exosome release NLRP3 inflammasome activation in podocytes may not produce local glomerular inflammatory response and associated injury during hHcy. Support or Funding Information This study was supported by NIH grants DK54927 and DK102539.

Release and Actions of Inflammatory Exosomes in Pulmonary Emphysema: Potential Therapeutic Target of Acupuncture

“…Some previous studies also demonstrated that the pro-inflammatory products are segregated into membrane-enclosed compartments and secreted into exosomes, which participate in the pathogenic process of different inflammatory or degenerative diseases. [66][67][68] There is evidence that this inflammasome-driven unconventional, vesicle-mediated secretion of immunoregulatory proteins or cytokines constitutes a novel paradigm for understanding inflammatory responses. 69 In previous studies, it has been shown that acid sphingomyelinase (ASM) and ceramide critically regulate NLRP3 inflammasome activation and related exosome release.…”

Endothelial Acid Sphingomyelinase Promotes NLRP3 Inflammasome and Neointima Formation During Hypercholesterolemia

“…Eight- to 12-week-old male and female C57BL/6J WT (WT/WT), Smpd1 trg /WT mice, and EC-specific Smpd1 transgenic mice were used in the current study. EC-specific Smpd1 transgenic mice were generated by crossbreeding EC-specific Cre transgenic (Tie2 [tunica intima endothelial kinase 2]-Cre) mice with Smpd1 trg /WT mice and genotyped in a similar method as we described for other tissue-specific transgenic mice with Smpd1 gene overexpression in podocytes ( 25 ) and smooth muscle cells ( 26 ). Mice were maintained in a controlled environment of 20°C and 40–50% humidity, with a 12-h light/dark cycle.…”