Background: Hyperhomocysteinemia (hHcys) contributes to glomerular injury by activating NLRP3 inflammasomes in response to increased oxidative stress. Results: Thioredoxin-interacting protein (TXNIP) aggregated with NLRP3 inflammasomes, and blocking TXNIP prevented inflammasome activation during hHcys. Conclusion: TXNIP uniquely links changes in oxidative stress to hHcys-induced NLRP3 inflammasome activation. Significance: Glomerular injury related to hHcys can be prevented by TXNIP inhibition.

Background: Chronic inflammatory conditions like obesity may adversely impact the biological functions underlying the regenerative potential of mesenchymal stromal/stem cells (MSC). Obesity can impair MSC function by inducing cellular senescence, a growth-arrest program that transitions cells to a pro-inflammatory state. However, the effect of obesity on adipose tissue-derived MSC in human subjects remains unclear. We tested the hypothesis that obesity induces senescence and dysfunction in human MSC. Methods: MSC were harvested from abdominal subcutaneous fat collected from obese and age-matched non-obese subjects (n = 40) during bariatric or kidney donation surgeries, respectively. MSC were characterized, their migration and proliferation assessed, and cellular senescence evaluated by gene expression of cell-cycle arrest and senescence-associated secretory phenotype markers. In vitro studies tested MSC effect on injured human umbilical vein endothelial cells (HUVEC) function. Results: Mean age was 59 ± 8 years, 66% were females. Obese subjects had higher body-mass index (BMI) than non-obese. MSC from obese subjects exhibited lower proliferative capacities than non-obese-MSC, suggesting decreased function, whereas their migration remained unchanged. Senescent cell burden and phenotype, manifested as p16, p53, IL-6, and MCP-1 gene expression, were significantly upregulated in obese subjects' MSC. BMI correlated directly with expression of p16, p21, and IL-6. Furthermore, co-incubation with non-obese, but not with obese-MSC, restored VEGF expression and tube formation that were blunted in injured HUVEC. Conclusion: Human obesity triggers an early senescence program in adipose tissue-derived MSC. Thus, obesity-induced cellular injury may alter efficacy of this endogenous repair system and hamper the feasibility of autologous transplantation in obese individuals.

The nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome has been implicated in podocyte injury and glomerular sclerosis during hyperhomocysteinemia (hHcys). However, it remains unclear whether the NLRP3 inflammasome can be a therapeutic target for treatment of hHcys-induced kidney injury. Given that DHA metabolites-resolvins have potent anti-inflammatory effects, the present study tested whether the prototype, resolvin D1 (RvD1), and 17S-hydroxy DHA (17S-HDHA), an intermediate product, abrogate hHcys-induced podocyte injury by targeting the NLRP3 inflammasome. In vitro, confocal microscopy demonstrated that 17S-HDHA (100 nM) and RvD1 (60 nM) prevented Hcys-induced formation of NLRP3 inflammasomes, as shown by reduced colocalization of NLRP3 with apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) or caspase-1. Both DHA metabolites inhibited Hcys-induced caspase-1 activation and interleukin-1β production. However, DHA had no significant effect on these Hcys-induced changes in podocytes. In vivo, DHA lipoxygenase metabolites substantially inhibited podocyte NLRP3 inflammasome formation and activation and consequent glomerular sclerosis in mice with hHcys. Mechanistically, RvD1 and 17S-HDHA were shown to suppress Hcys-induced formation of lipid raft redox signaling platforms and subsequent O production in podocytes. It is concluded that inhibition of NLRP3 inflammasome activation is one of the important mechanisms mediating the beneficial action of RvD1 and 17S-HDHA on Hcys-induced podocyte injury and glomerular sclerosis.

The intracellular multiprotein complex termed the inflammasome functions as a platform of pro-inflammatory cytokine production such as IL-1β and IL-18. Under certain conditions, however, the inflammasome produces non-canonical effects such as induction of cell death, pyroptosis and cell metabolism alterations. In mammalian cells, several types of inflammasomes were identified, but the most widely studied one is the inflammasome containing NOD-like receptor with pyrin domain 3 (NLRP3), which has recently been reported as a central pathogenic mechanism of chronic degenerative diseases. Many activators or danger factors exert their actions through activation of the NLRP3 inflammasome to produce a variety of functional changes in different cells including inflammatory, metabolic or survival responses. Several molecular signaling pathways are shown to mediate the activation of the NLRP3 inflammasome, and they are related to the modifications in K+ efflux, increased lysosome leakage and activation of cathepsin B or enhanced reactive oxygen species (ROS) production. In the kidney, inflammation is believed to mediate or promote the progression of glomerular sclerotic pathologies resulting in end-stage renal disease (ESRD). NLRP3 inflammasome activation may turn on glomerular inflammation and other cell damages, contributing to the onset of glomerular injury and ESRD. This inflammasome activation not only occurs in immune cells, but also in residential cells such as endothelial cells and podocytes in the glomeruli. This review briefly summarizes current evidence of NLRP3 inflammasome activation and related molecular mechanisms in renal glomeruli. The possible canonical and non-canonical effects of this inflammasome activation and its potential implication in the development of different glomerular diseases are highlighted.

Novel therapies are needed to address the increasing prevalence of chronic kidney disease. Mesenchymal stem/ stromal cells (MSCs) and MSC-derived extracellular vesicles (EVs) augment tissue repair. We tested the hypothesis that EVs are as effective as MSCs in protecting the stenotic kidney, but target different injury pathways. Pigs were studied after 16 weeks of renal injury achieved by diet-induced metabolic syndrome (MetS) and renal artery stenosis (RAS). Pigs were untreated or treated 4 weeks earlier with intrarenal delivery of autologous adipose tissue-derived MSCs (10 7 ) or their EVs (10 11 ). Lean pigs and sham RAS served as controls (n = 6 each). Stenotic-kidney function was studied in vivo using computed tomography and magnetic resonance imaging. Histopathology and expression of necroptosis markers [receptor-interacting protein kinase (RIPK)-1 and RIPK-3], inflammatory, and growth factors (angiopoietin-1 and vascular endothelial growth factor) were studied ex vivo. Stenotic-kidney glomerular filtration rate and blood flow in MetS + RAS were both lower than Lean and increased in both MetS + RAS + MSC and MetS + RAS + EV. Both MSCs and EV improved renal function and decreased renal hypoxia, fibrosis, and apoptosis. MSCs were slightly more effective in preserving microvascular (0.02-0.2 mm diameters) density and prominently attenuated renal inflammation. However, EV more significantly upregulated growth factor expression and decreased necroptosis. In conclusion, adipose tissue-derived MSCs and their EV both improve stenotic kidney function and decrease tissue injury in MetS + RAS by slightly different mechanisms. MSCs more effectively preserved the microcirculation, while EV bestowed better preservation of renal cellular integrity. These findings encourage further exploration of this novel approach to attenuate renal injury.