Protein level expression of Toll-like receptors 2, 4 and 9 in renal disease

SBP1 contributes to mesangial proliferation and inflammation through mitochondrial respiration in glomerulus during IgA nephropathy

Mesangial expansion and proliferation have been implicated in the pathogenesis of IgA nephropathy (IgAN). Mesangial cells in glomerulus are important contributors to commencement of IgAN. From minimal mesangial expansion to diffuse proliferation, the mesangial alteration is linked to clinical and pathological features of IgAN. Although selenium-binding protein 1 (SBP1) is associated with tissue injury, the roles of SBP1 in mesangial proliferation and inflammation in glomerulus during IgAN remains unclear. In the present study, we found that SBP1 gene levels were elevated in kidney tissues of patients with IgAN. Also, SBP1 protein levels were elevated in proliferative mesangial cells of glomerulus in kidney tissues from patients with IgAN. Urinary SBP1 protein levels were elevated in patients with IgAN. Elevated urinary SBP1 levels were positively correlated with segmental glomerulosclerosis of the Oxford classification related to mesangial proliferation in patients with IgAN. Over-expression of SBP1 induced cellular proliferation via mitochondrial respiration in human renal mesangial cells. Consistently, SBP1 knockdown and mitochondrial respiration inhibition suppressed cellular proliferation and induced mitochondrial oxidative stress in human renal mesangial cells. Furthermore, SBP1 induced pro-inflammatory phenotype by gene expression and production of pro-inflammatory cytokines and chemokines including IL-6, CXCL10, and CCL5 via NF-κB activation in human renal mesangial cells. These results suggest that SBP1 contributes to mesangial proliferation and inflammation via mitochondrial respiration during IgAN.

Role of the Innate Immune Response in Glomerular Disease Pathogenesis: Focus on Podocytes

Accumulating evidence indicates that inflammatory and immunologic processes play a significant role in the development and progression of glomerular diseases. Podocytes, the terminally differentiated epithelial cells, are crucial for maintaining the integrity of the glomerular filtration barrier. Once injured, podocytes cannot regenerate, leading to progressive proteinuric glomerular diseases. However, emerging evidence suggests that podocytes not only maintain the glomerular filtration barrier and are important targets of immune responses but also exhibit many features of immune-like cells, where they are involved in the modulation of the activity of innate and adaptive immunity. This dual role of podocytes may lead to the discovery and development of new therapeutic targets for treating glomerular diseases. This review aims to provide an overview of the innate immunity mechanisms involved in podocyte injury and the progression of proteinuric glomerular diseases.

Toll-like receptors and nuclear factor kappa B signaling pathway involvement in hepatorenal oxidative damage induced by some food preservatives in rats

Chemical food preservatives are extensively found in various processed food products in the human environment. Hence, this study aimed to investigate the effect of long-term exposure to five food preservatives (potassium sorbate (PS), butylated hydroxyanisole (BHA), sodium benzoate (SB), calcium propionate (CP), and boric acid (BA)) on the liver and kidney in rats and the probable underlying mechanisms. For 90 days, sixty male albino rats were orally given either water (control), 0.09 mg/kg b.wt BHA, 4.5 mg/kg b.wt PS, 0.9 mg/kg b.wt SB, 0.16 mg/kg b.wt BA, or 0.18 mg/kg b.wt CP. Liver and kidney function tests were assessed. Hepatic and renal oxidative stress biomarkers were estimated. Histologic examination analysis of liver and kidney tissues was achieved. Toll-like receptors 2 and 4 (TLR-2 and TLR-4), tumor necrosis factor-alpha (TNF-α), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) mRNA expression levels were measured. The results revealed that long-term oral dosing of the five food preservatives resulted in significant increases in alkaline phosphatase, alanine transaminase, aspartate transaminase, urea, uric acid, and creatinine levels. There were significant reductions in hepatic and renal antioxidant enzymes, an increase in MDA concentrations, and pathological alterations in renal and hepatic tissues. The mRNA levels of TLR-4, TLR-2, NF-κB, and TNF-α were elevated in the food preservatives-exposed groups. Conclusively, the current findings revealed that long-term exposure to PS, BHA, SB, CP, and BA has a negative impact on liver and kidney function. Furthermore, these negative effects could be mediated via oxidative stress induction, inflammatory reactions, and cytokine production.

LncRNA SNHG16 regulates RAS and NF-κB pathway-mediated NLRP3 inflammasome activation to aggravate diabetes nephropathy through stabilizing TLR4

AIMS

LncRNA SNHG16 and Toll-like receptor-4 (TLR4) participate in diabetes nephropathy. This study investigated whether SNHG16 regulates diabetic renal injury (DRI) via TLR4 and its related mechanism.

METHODS

Diabetic mice and high glucose (HG)-induced HRMCs were used to examine the expressions of SNHG16 and TLR4. The SNHG16 expression, cytokines, reactive oxygen species, MDA, SOD, GSH, and fibrosis-related proteins were evaluated in HG-induced HRMCs transfected with sh-NC or sh-SHNG16. RNA immunoprecipitation and RNA pull-down determined the interaction between SNHG16 and EIF4A3 or TLR4 and EIF4A3. We used HG-treated HRMCs or diabetic mice to investigate the roles of TLR4 or SNHG16 in renal injuries.

RESULTS

Both SNHG16 and TLR4 were upregulated in diabetic conditions. HG increased serum Scr and BUN, led to significant fibrosis, increased inflammation- and renal fibrosis-related proteins in mice, and increased ROS, MDA, and decreased SOD and GSH in HRMCs. SNHG16 silencing diminished HG-upregulated SNHG16, decreased HG-increased cytokines secretion, ROS, MDA, and fibrosis but increased SOD and GSH. RIP and RNA pull-down confirmed that SNHG16 recruits EIF4A3 to stabilize TLR4 mRNA. TLR4 knockdown alleviated HG-induced renal injuries by suppressing RAS and NF-κB-mediated activation of NLRP3 inflammasomes. SNHG16 knockdown alleviated HG-induced renal injuries in HG-induced HRMCs or diabetic mice. Interestingly, TLR4 overexpression reversed the effects of SNHG16 knockdown. Mechanistically, SNHG16 knockdown alleviated HG-induced renal injuries by suppressing TLR4.

CONCLUSION

SNHG16 accelerated HG-induced renal injuries via recruiting EIF4A3 to enhance the stabilization of TLR4 mRNA. The SNGHG16/ELF4A3/TLR4 axis might be a novel target for treating DRI.

Mitochondrial Contribution to Inflammation in Diabetic Kidney Disease

Diabetes is the leading cause of chronic kidney disease worldwide. Despite the burden, the factors contributing to the development and progression of diabetic kidney disease (DKD) remain to be fully elucidated. In recent years, increasing evidence suggests that mitochondrial dysfunction is a pathological mediator in DKD as the kidney is a highly metabolic organ rich in mitochondria. Furthermore, low grade chronic inflammation also contributes to the progression of DKD, and several inflammatory biomarkers have been reported as prognostic markers to risk-stratify patients for disease progression and all-cause mortality. Interestingly, the term "sterile inflammation" appears to be used in the context of DKD describing the development of intracellular inflammation in the absence of bacterial or viral pathogens. Therefore, a link between mitochondrial dysfunction and inflammation in DKD exists and is a hot topic in both basic research and clinical investigations. This review summarizes how mitochondria contribute to sterile inflammation in renal cells in DKD.

Multifaceted roles of Toll-like receptors in acute kidney injury

Toll-like receptors (TLRs) are a family of pattern recognition receptors (PRRs) in the first line defense system of our bodies; they are widely expressed on leukocytes and kidney epithelial cells. Infections due to pathogens or danger signals from injured tissues often activate several TLRs and these receptors mediate their signal transduction through the activation of transcription factors that regulate the expression of cytokine interleukin-1β (IL-1β), type I interferons (IFNs), and nuclear factor kappa light chain enhancer of activated B cells (NF-κB) dependent cytokines and chemokines. Acute kidney injury (AKI) involves early Toll-like receptors driven immunopathology, while resolution of inflammation is needed for rapid regeneration of injured tubular cells. Despite their well known function in the progression of inflammation; interestingly, activation of TLRs also has been implicated in renal epithelial repair through the induction of certain interleukins and improvement in autophagy mechanism. Studies have found that although the blockade of TLRs during the early injury phase of renal tissues prevented tubular necrosis, suppression of interleukins production and impaired kidney regeneration due to their blockade has been observed during the healing phase of tissue. Taken together, these results suggest that the two danger response programs of renal cells i.e. renal inflammation and regeneration may link at the level of TLRs. This review aims to emphasize on the role of TLRs signaling in different acute kidney injury phases. Understanding of these pathways may turn out to be effective as therapeutic option for kidney diseases.

The immune podocyte

PURPOSE OF REVIEW

Lupus nephritis (LN) is a serious manifestation of systemic lupus erythematosus and is characterized by proteinuria and renal failure. Proteinuria is a marker of poor prognosis and is attributed to podocyte loss and dysfunction. It is often debated whether these cells are innocent bystanders or active participants in the pathogenesis of glomerulonephritis.

RECENT FINDINGS

Podocytes share many elements of the innate and adaptive immune system. Specifically, they produce and express complement components and receptors which when dysregulated appear to contribute to podocyte damage and LN. In parallel, podocytes express major histocompatibility complex and co-stimulatory molecules which may be involved in local immune events. Podocyte-specific cytotoxic cells and possibly other immune cells contribute to glomerular damage. Autoantibodies present in lupus sera enter podocytes to upregulate calcium/calmodulin kinase which in turn compromises their structure and function.

SUMMARY

More recent studies point to the restoration of podocyte function using cell targeted approaches to prevent and treat LN. These strategies along with podocyte involvement in the pathogenesis of LN will be addressed in this review.

The Role of TLR4 Asp299Gly and TLR4 Thr399Ile Polymorphisms in the Pathogenesis of Urinary Tract Infections: First Evaluation in Infants and Children of Greek Origin

Urinary tract infections are one of the most common and serious bacterial infections in a pediatric population. So far, they have mainly been related to age, gender, ethnicity, socioeconomic level, and the presence of underlying anatomical or functional, congenital, or acquired abnormalities. Recently, both innate and adaptive immunities and their interaction in the pathogenesis and the development of UTIs have been studied. The aim of this study was to assess the role and the effect of the two most frequent polymorphisms of TLR4 Asp299Gly and Thr399Ile on the development of UTIs in infants and children of Greek origin. We studied 51 infants and children with at least one episode of acute urinary tract infection and 109 healthy infants and children. We found that 27.5% of patients and 8.26% of healthy children carried the heterozygote genotype for TLR4 Asp299Gly. TLR4 Thr399Ile polymorphism was found to be higher in healthy children and lower in the patient group. No homozygosity for both studied polymorphisms was detected in our patients. In the group of healthy children, a homozygote genotype for TLR4 Asp299Gly (G/G) as well as for TLR4 Thr399Ile (T/T) was showed (1.84% and 0.92 respectively). These results indicate the role of TLR4 polymorphism as a genetic risk for the development of UTIs in infants and children of Greek origin.

TLR2 and TLR4 play opposite role in autophagy associated with cisplatin-induced acute kidney injury

Acute kidney injury (AKI) is considered an inflammatory disease in which toll-like receptors (TLRs) signaling pathways play an important role. The activation of TLRs results in production of several inflammatory cytokines leading to further renal damage. In contrast, TLRs are key players on autophagy induction, which is associated with a protective function on cisplatin-induced AKI. Hence, the present study aimed to evaluate the specific participation of TLR2 and TLR4 molecules on the development of cisplatin-induced AKI. Complementarily, we also investigated the link between TLRs and heme oxygenase-1 (HO-1), a promisor cytoprotective molecule. First, we observed that only the absence of TLR2 but not TLR4 in mice exacerbated the renal dysfunction, tissue injury and mortality rate, even under an immunologically privileged microenvironment. Second, we demonstrated that TLR2 knockout (KO) mice presented lower expression of autophagy-associated markers when compared with TLR4 KO animals. Similar parameter was confirmed in vitro, using tubular epithelial cells derived from both KO mice. To test the cross-talking between HO-1 and TLRs, hemin (an HO-1 internal inducer) was administrated in cisplatin-treated TLR2 and TLR4 KO mice and it was detected an improvement in the global renal tissue parameters. However, this protection was less evident at TLR2 KO mice. In summary, we documented that TLR2 plays a protective role in cisplatin-induced AKI progression, in part, by a mechanism associated with autophagy up-regulation, considering that its interplay with HO-1 can promote renal tissue recover.

Metabonomics analysis of quercetin against the nephrotoxicity of acrylamide in rats

This research aimed at studying the effect of quercetin against the nephrotoxicity of acrylamide by metabonomics analysis of kidney tissue.

Innate Immune Activity in Glomerular Podocytes

Glomerular podocytes are specialized in structure and play an essential role in glomerular filtration. In addition, podocyte stress can initiate glomerular damage by inducing the injury of other glomerular cell types. Studies have shown that podocytes possess the property of immune cells and may be involved in adaptive immunity. Emerging studies have also shown that podocytes possess signaling pathways of innate immune responses and that innate immune responses often result in podocyte injury. More recently, mitochondrial-derived damage-associated molecular patterns (mtDAMPs) have been shown to play a critical role in a variety of pathological processes in cells. In the present mini-review, we summarize the recent advances in the studies of innate immunity and its pathogenic role in podocytes, particularly, from the perspective of mtDAMPs.

Effect of Rhizoma Polygoni Cuspidati and Ramulus Cinnamomi compatibility on uric acid metabolism and urinary neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 in rats with hyperuricemia

OBJECTIVE

To explore the effects of Rhizoma Polygoni Cuspidati and Ramulus Cinnamomi compatibility (PR) on uric acid metabolism and the expression of urinary neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) in rats with hyperuricemia.

METHODS

Seventy male Sprague Dawley (SD) rats were randomly divided into 7 groups with 10 rats per group, including the normal group, model group, allopurinol group, benzbromarone group and PR groups at 3 doses (3.5, 7, 14 g/kg). Except the normal group, rats of the other groups were intragastrically administered 100 mg/kg hypoxanthine and 250 mg/kg ethambutol, and subcutaneously injected with 200 mg/kg potassium oxonate. All rats were continuously modeled for 17 days, and gavaged with corresponding drugs. The rats of the normal and model groups were gavaged with saline, once a day, for 2 weeks. The levels of serum uric acid (SUA), blood urea nitrogen (BUN) and creatinine (Cr) were determined. In addition, the contents of NGAL and KIM-1 in urine and the mRNA and protein expressions of xanthine oxidase (XOD) in liver of hyperuricemia rats were measured by reverse transcription polymerase chain reaction (RT-PCR) and Western blot, respectively. Moreover, the pathological changes of kidney were analyzed by hematoxylin and eosin (HE) stain method.

RESULTS

Compared with the normal group, the levels of SUA, BUN, NGAL and KIM-1 and the expressions of hepatic XOD mRNA and protein in the hyperuricemia rats were increased signifificantly (P<0.01). PR signifificantly decreased the levels of SUA, BUN, NGAL and KIM-1 and down-regulated the mRNA and protein expressions of hepatic XOD (P<0.05 or P<0.01). In addition, the pathological changes of kidney were signifificantly suppressed by oral administration of PR.

CONCLUSIONS

PR ameliorated uric acid metabolism and protected renal function, the underlying mechanism was mediated by decreasing the levels of SUA, BUN, NGAL and KIM-1, inhibiting the expression of hepatic XOD and ameliorating the pathological change of kidney.

Toll-like Receptor 9 Can be Activated by Endogenous Mitochondrial DNA to Induce Podocyte Apoptosis

Toll-like receptor 9 (TLR9) senses bacterial DNA characteristic of unmethylated CpG motifs to induce innate immune response. TLR9 is de novo expressed in podocytes of some patients with glomerular diseases, but its role in podocyte injury remains undetermined. Since TLR9 activates p38 MAPK and NFkB that are known to mediate podocyte apoptosis, we hypothesized that TLR9 induces podocyte apoptosis in glomerular diseases. We treated immortalized podocytes with puromycin aminonucleosides (PAN) and observed podocyte apoptosis, accompanied by TLR9 upregulation. Prevention of TLR9 upregulation by siRNA significantly attenuated NFκB p65 or p38 activity and apoptosis, demonstrating that TLR9 mediates podocyte apoptosis. We next showed that endogenous mitochondrial DNA (mtDNA), whose CpG motifs are also unmethylated, is the ligand for TLR9, because PAN induced mtDNA accumulation in endolysosomes where TLR9 is localized, overexpression of endolysosomal DNase 2 attenuated PAN-induced p38 or p65 activity and podocyte apoptosis, and DNase 2 silencing was sufficient to activate p38 or p65 and induce apoptosis. In PAN-treated rats, TLR9 was upregulated in the podocytes, accompanied by increase of apoptosis markers. Thus, de novo expressed TLR9 may utilize endogenous mtDNA as the ligand to facilitate podocyte apoptosis, a novel mechanism underlying podocyte injury in glomerular diseases.

Albumin stimulates renal tubular inflammation through an HSP70-TLR4 axis in mice with early diabetic nephropathy

Increased urinary albumin excretion is not simply an aftermath of glomerular injury, but is also involved in the progression of diabetic nephropathy (DN). Whereas Toll-like receptors (TLRs) are incriminated in the renal inflammation of DN, whether and how albumin is involved in the TLR-related renal inflammatory response remains to be clarified. Here, we showed that both TLR2 and TLR4, one of their putative endogenous ligands [heat shock protein 70 (HSP70)] and nuclear factor-κB promoter activity were markedly elevated in the kidneys of diabetic mice. A deficiency of TLR4 but not of TLR2 alleviated albuminuria, tubulointerstitial fibrosis and inflammation induced by diabetes. The protection against renal injury in diabetic Tlr4^−/− mice was associated with reduced tubular injuries and preserved cubilin levels, rather than amelioration of glomerular lesions. In vitro studies revealed that albumin, a stronger inducer than high glucose (HG), induced the release of HSP70 from proximal tubular cells. HSP70 blockade ameliorated albumin-induced inflammatory mediators. HSP70 triggered the production of inflammatory mediators in a TLR4-dependent manner. Moreover, HSP70 inhibition in vivo ameliorated diabetes-induced albuminuria, inflammatory response and tubular injury. Finally, we found that individuals with DN had higher levels of TLR4 and HSP70 in the dilated tubules than non-diabetic controls. Thus, activation of the HSP70-TLR4 axis, stimulated at least in part by albumin, in the tubular cell is a newly identified mechanism associated with induction of tubulointerstitial inflammation and aggravation of pre-existing microalbuminuria in the progression of DN.

Summary: Activation of the HSP70-TLR4 axis by albumin in the tubular cell induces tubular inflammation and injury.

Shiga toxin pathogenesis: kidney complications and renal failure

The kidneys are the major organs affected in diarrhea-associated hemolytic uremic syndrome (D(+)HUS). The pathophysiology of renal disease in D(+)HUS is largely the result of the interaction between bacterial virulence factors such as Shiga toxin and lipopolysaccharide and host cells in the kidney and in the blood circulation. This chapter describes in detail the current knowledge of how these bacterial toxins may lead to kidney disease and renal failure. The toxin receptors expressed by specific blood and resident renal cell types are also discussed as are the actions of the toxins on these cells.

The T-1237C polymorphism of the Toll-like receptor-9 gene is associated with chronic kidney disease in a Han Chinese population

Chronic kidney disease (CKD) is increasingly recognized as a global public health problem. As inflammatory processes and genetic factors are involved in the pathogenesis of CKD, we have investigated the potential genetic contribution of Toll-like receptor (TLR) gene polymorphisms in CKD. In a case-control association study, 149 CKD patients and 429 healthy controls were genotyped by real-time polymerase chain reaction. CKD patients were defined as kidney damage (albuminuria, proteinuria or hematuria) or glomerular filtration rate < 60 ml/min/1.73 m(2) for 3 months or more. Single nucleotide polymorphisms (SNPs) at TLR-2 G2408A, TLR-4 A12874G and C13174T, and TLR-9 T-1237C, T-1486C, and G1635A were assessed, and linkage disequilibrium calculations and haplotype association analysis were undertaken. The functions of TLR-9 have been documented to recognize the viral and bacterial CpG DNA sequences, whereas detects microbe-derived peptidoglycan and lipopeptides and TLR-4 binds lipopolysaccharides. SNPs within the TLR genes may influence promoter activity, mRNA conformation and subcellular localization, and/or protein structure and function. Our results show that only the TLR-9 T-1237C and G1635A gene polymorphisms demonstrate an association with CKD (p = 0.002 and p = 0.04, respectively). The TLR-9 TCA haplotype at T-1237C, T-1486C, and G1635A was associated with a lower risk of CKD, whereas the TTA haplotype was associated with a higher risk of CKD. In the Han Chinese population, those who carry the C and A alleles at SNPs T-1237C and G1635A in the TLR-9 gene appear to be more susceptible to the development of CKD.