Toll-Like Receptors Regulate the Development and Progression of Renal Diseases

Caffeic acid alleviates skeletal muscle atrophy in 5/6 nephrectomy rats through the TLR4/MYD88/NF-kB pathway

Skeletal muscle atrophy is a common complication of chronic kidney disease (CKD) that affects the quality of life and prognosis of patients. We aimed to investigate the effects and mechanisms of caffeic acid (CA), a natural phenolic compound, on skeletal muscle atrophy in CKD rats. Male Sprague-Dawley rats underwent 5/6 nephrectomy (NPM) and were treated with CA (20, 40, or 80 mg/kg/day) for 10 weeks. The body and muscle weights, renal function, hemoglobin, and albumin were measured. The histological, molecular, and biochemical changes in skeletal muscles were evaluated using hematoxylin-eosin staining, quantitative real-time PCR, malondialdehyde/catalase/superoxide dismutase/glutathione level detection, and enzyme-linked immunosorbent assay. Western blotting and network pharmacology were applied to identify the potential targets and pathways of CA, CKD, and muscle atrophy. The results showed that CA significantly improved NPM-induced muscle-catabolic effects, reduced the expression of muscle atrophy-related proteins (muscle atrophy F-box and muscle RING finger 1) and proinflammatory cytokines (interleukin [IL]-6, tumor necrosis factor-alpha, and IL-1β), and attenuated muscle oxidative stress. Network pharmacology revealed that CA modulated the response to oxidative stress and nuclear factor kappa B (NF-κB) signaling pathway and that Toll-like receptor 4 (TLR4) was a key target. In vivo experiment confirmed that CA inhibited the TLR4/myeloid differentiation primary response 88 (MYD88)/NF-kB signaling pathway, reduced muscle iron levels, and restored glutathione peroxidase 4 activity, thereby alleviating ferroptosis and inflammation in skeletal muscles. Thus, CA might be a promising therapeutic agent for preventing and treating skeletal muscle atrophy in CKD by modulating the TLR4/MYD88/NF-κB pathway and ferroptosis.

The immunoregulatory roles of non-haematopoietic cells in the kidney

The deposition of immune complexes, activation of complement and infiltration of the kidney by cells of the adaptive and innate immune systems have long been considered responsible for the induction of kidney damage in autoimmune, alloimmune and other inflammatory kidney diseases. However, emerging findings have highlighted the contribution of resident immune cells and of immune molecules expressed by kidney-resident parenchymal cells to disease processes. Several types of kidney parenchymal cells seem to express a variety of immune molecules with a distinct topographic distribution, which may reflect the exposure of these cells to different pathogenic threats or microenvironments. A growing body of literature suggests that these cells can stimulate the infiltration of immune cells that provide protection against infections or contribute to inflammation - a process that is also regulated by draining kidney lymph nodes. Moreover, components of the immune system, such as autoantibodies, cytokines and immune cells, can influence the metabolic profile of kidney parenchymal cells in the kidney, highlighting the importance of crosstalk in pathogenic processes. The development of targeted nanomedicine approaches that modulate the immune response or control inflammation and damage directly within the kidney has the potential to eliminate the need for systemically acting drugs.

The Terminalia chebula Retz extract treats hyperuricemic nephropathy by inhibiting TLR4/MyD88/NF-κB axis

ETHNOPHARMACOLOGICAL RELEVANCE

Hyperuricemic nephropathy (HN) is a renal injury caused by hyperuricemia and is the main cause of chronic kidney disease and end-stage renal disease. ShiWeiHeZiSan, which is composed mainly of components of Terminalia chebula Retz. And is recorded in the Four Medical Tantras, is a typical traditional Tibetan medicinal formula for renal diseases. Although T. chebula has been reported to improve renal dysfunction and reduce renal cell apoptosis, the specific mechanism of the nephroprotective effects of T. chebula on HN is still unclear.

AIM OF THE STUDY

This study was conducted to evaluate the effects and specific mechanism of T. chebula extract on HN through network pharmacology and in vivo and in vitro experiments.

MATERIALS AND METHODS

Potassium oxalate (1.5 g/kg) and adenine (50 mg/kg) were combined for oral administration to establish the HN rat model, and the effects of T. chebula extract on rats in the HN model were evaluated by renal function indices and histopathological examinations. UPLC-Q-Exactive Orbitrap/MS analysis was also conducted to investigate the chemical components of T. chebula extract, and the potential therapeutic targets of T. chebula in HN were predicted by network pharmacology analysis. Moreover, the activation of potential pathways and the expression of related mRNAs and proteins were further observed in HN model rats and uric acid-treated HK-2 cells.

RESULTS

T. chebula treatment significantly decreased the serum uric acid (SUA), blood urea nitrogen (BUN) and serum creatinine (SCr) levels in HN rats and ameliorated renal pathological injury and fibrosis. A total of 25 chemical components in T. chebula extract were identified by UPLC-Q-Exactive Orbitrap/MS analysis, and network pharmacology analysis indicated that the NF-κB pathway was the potential pathway associated with the therapeutic effects of T. chebula extract on HN. RT‒PCR analysis, immunofluorescence staining and ELISA demonstrated that the mRNA and protein levels of TLR4 and MyD88 were significantly decreased in the renal tissue of HN rats after treatment with T. chebula extract at different concentrations, while the phosphorylation of P65 and the secretion of TNF-α and IL-6 were significantly inhibited. The results of in vitro experiments showed that T. chebula extract significantly decreased the protein levels of TLR4, MyD88, p-IκBα and p-P65 in uric acid-treated HK-2 cells and inhibited the nuclear translocation of p65 in these cells. In addition, the expression of inflammatory factors (IL-1β, IL-6 and TNF-α) and fibrotic genes (α-SMA and fibronectin) was significantly downregulated by T. chebula extract treatment, while E-cadherin expression was significantly upregulated.

CONCLUSION

T. chebula extract exerts nephroprotective effects on HN, such as anti-inflammatory effects and fibrosis improvement, by regulating the TLR4/MyD88/NF-κB axis, which supports the general use of T. chebula in the management of HN and other chronic kidney diseases.

Catalpol ameliorates fructose-induced renal inflammation by inhibiting TLR4/MyD88 signaling and uric acid reabsorption

Accumulating evidence suggests that excess fructose uptake induces metabolic syndrome and kidney injury. Here, we primarily investigated the influence of catalpol on fructose-induced renal inflammation in mice and explored its potential mechanism. Treatment with catalpol improved insulin sensitivity and hyperuricemia in fructose-fed mice. Hyperuricemia induced by high-fructose diet was associated with increases in the expressions of urate reabsorptive transporter URAT1 and GLUT9. Treatment with catalpol decreased the expressions of URAT1 and GLUT9. Futhermore, treatment with catalpol ameliorated renal inflammatory cell infiltration and podocyte injury, and these beneficial effects were associated with inhibiting the production of inflammatory cytokines including IL-1β, IL-18, IL-6 and TNF-α. Moreover, fructose-induced uric acid triggers an inflammatory response by activiting NLRP3 inflammasome, which then processes pro-inflammatory cytokines. Treatment with catalpol could inhibit the activation of NLRP3 inflammasome as well. Additionally, TLR4/MyD88 signaling was activated in fructose-fed mice, while treatment with catalpol inhibited this activation along with promoting NF-κB nuclear translocation in fructose-fed mice. Thus, our study demonstrated that catalpol could ameliorate renal inflammation in fructose-fed mice, attributing its beneficial effects to promoting uric acid excretion and inhibit the activation of TLR4/MyD88 signaling.

Type I IFN in Glomerular Disease: Scarring beyond the STING

The field of nephrology has recently directed a considerable amount of attention towards the stimulator of interferon genes (STING) molecule since it appears to be a potent driver of chronic kidney disease (CKD). STING and its activator, the cyclic GMP-AMP synthase (cGAS), along with intracellular RIG-like receptors (RLRs) and toll-like receptors (TLRs), are potent inducers of type I interferon (IFN-I) expression. These cytokines have been long recognized as part of the mechanism used by the innate immune system to battle viral infections; however, their involvement in sterile inflammation remains unclear. Mounting evidence pointing to the involvement of the IFN-I pathway in sterile kidney inflammation provides potential insights into the complex interplay between the innate immune system and damage to the most sensitive segment of the nephron, the glomerulus. The STING pathway is often cited as one cause of renal disease not attributed to viral infections. Instead, this pathway can recognize and signal in response to host-derived nucleic acids, which are also recognized by RLRs and TLRs. It is still unclear, however, whether the development of renal diseases depends on subsequent IFN-I induction or other processes involved. This review aims to explore the main endogenous inducers of IFN-I in glomerular cells, to discuss what effects autocrine and paracrine signaling have on IFN-I induction, and to identify the pathways that are implicated in the development of glomerular damage.

TLR2 mediates renal apoptosis in neonatal mice subjected experimentally to obstructive nephropathy

Urinary tract obstruction during renal development leads to inflammation, tubular apoptosis, and interstitial fibrosis. Toll like receptors (TLRs) expressed on leukocytes, myofibroblasts and renal cells play a central role in acute inflammation. TLR2 is activated by endogenous danger signals in the kidney; its contribution to renal injury in early life is still a controversial topic. We analyzed TLR2 for a potential role in the neonatal mouse model of congenital obstructive nephropathy. Inborn obstructive nephropathies are a leading cause of end-stage kidney disease in children. Thus, newborn Tlr2-/- and wild type (WT) C57BL/6 mice were subjected to complete unilateral ureteral obstruction (UUO) or sham-operation on the 2nd day of life. The neonatal kidneys were harvested and analyzed at days 7 and 14 of life. Relative expression levels of TLR2, caspase-8, Bcl-2, Bax, GSDMD, GSDME, HMGB1, TNF, galectin-3, α-SMA, MMP-2, and TGF-β proteins were quantified semi-quantitatively by immunoblot analyses. Tubular apoptosis, proliferation, macrophage- and T-cell infiltration, tubular atrophy, and interstitial fibrosis were analyzed immunohistochemically. Neonatal Tlr2-/- mice kidneys exhibited less tubular and interstitial apoptosis as compared to those of WT C57BL/6 mice after UUO. UUO induced neonatally did trigger pyroptosis in kidneys, however to similar degrees in Tlr2-/- and WT mice. Also, tubular atrophy, interstitial fibrosis, tubular proliferation, as well as macrophage and T-cell infiltration were unremarkable. We conclude that while TLR2 mediates apoptosis in the kidneys of neonatal mice subjected to UUO, leukocyte recruitment, interstitial fibrosis, and consequent neonatal obstructive nephropathy might lack a TLR2 involvement.

tRF-003634 alleviates adriamycin-induced podocyte injury by reducing the stability of TLR4 mRNA

Podocyte injury plays a key role in the production of proteinuria and is closely related to the progression of chronic kidney disease (CKD). Alleviating podocyte injury is beneficial to prevent the occurrence and development of CKD. tRNA-derived RNA fragments (tRFs) are associated with podocytes injury processes such as protein binding, cell adhesion, synapses, the actin cytoskeleton. Our previous data showed that tRF-003634 tightly correlated with podocyte injury, while its effect remains unclear. This study aimed to investigate the role of tRF-003634 in podocyte injury and the potential mechanisms. The expression level of tRF-003634, nephrin, podocin and tRF-003634 targeted toll-like receptor 4 (TLR4) in podocytes and kidney tissues were examined by quantitative real-time PCR (qRT-PCR), western blot and immunohistochemistry. The biochemical indices were monitored and renal pathological changes were assessed by hematoxylin and eosin PAS staining. Furthermore, potential target genes of tRF-003634 were screened using high-throughput mRNA sequencing, and then confirmed by RNA pulse-chase analysis. The results showed that tRF-003634 was downregulated in adriamycin (Adr)-induced podocyte injury. Overexpression of tRF-003634 increased the expression of nephrin and podocin in vivo and in vitro and alleviated podocyte injury. Meanwhile, overexpression of tRF-003634 alleviated proteinuria and renal pathological damage. In addition, high-throughput sequencing after overexpression of tRF-003634 showed that TLR4 might be a downstream target gene. tRF-003634 can alleviate podocyte injury by reducing the stability of TLR4 mRNA, possibly by competing with TLR4 mRNA to bind to YTH domain-containing protein 1 (YTHDC1). In conclusion, tRF-003634 was underexpressed in Adr-induced podocyte injury, and its overexpression alleviated podocyte injury in vitro and in vivo by reducing the stability of TLR4 mRNA.

CD8 T Cell-Derived Exosomal miR-186-5p Elicits Renal Inflammation via Activating Tubular TLR7/8 Signal Axis

T cells play an important role in the development of focal segmental glomerulosclerosis (FSGS). The mechanism underlying such T cell-based kidney disease, however, remains elusive. Here the authors report that activated CD8 T cells elicit renal inflammation and tissue injury via releasing miR-186-5p-enriched exosomes. Continuing the cohort study identifying the correlation of plasma level of miR-186-5p with proteinuria in FSGS patients, it is demonstrated that circulating miR-186-5p is mainly derived from activated CD8 T cell exosomes. Renal miR-186-5p, which is markedly increased in FSGS patients and mice with adriamycin-induced renal injury, is mainly delivered by CD8 T cell exosomes. Depleting miR-186-5p strongly attenuates adriamycin-induced mouse renal injury. Supporting the function of exosomal miR-186-5p as a key circulating pathogenic factor, intravenous injection of miR-186-5p or miR-186-5p-containing T cell exosomes results in mouse renal inflammation and tissue injury. Tracing the injected T cell exosomes shows their preferential distribution in mouse renal tubules, not glomerulus. Mechanistically, miR-186-5p directly activates renal tubular TLR7/8 signal and initiates tubular cell apoptosis. Mutating the TLR7-binding sequence on miR-186-5p or deleting mouse TLR7 largely abolishes renal tubular injuries induced by miR-186-5p or adriamycin. These findings reveal a causative role of exosomal miR-186-5p in T cell-mediated renal dysfunction.

The Renoprotective Effect of Shikonin in a Rat Model of Diabetic Kidney Disease

BACKGROUND

In diabetes mellitus, diabetic nephropathy (DN) is a typical complication and pivotal cause of chronic kidney disease. The DN disease burden is among the highest in the world and is associated with high morbidity, mortality, and disease burden. Safe and effective medications are urgently needed for the treatment of DN. Interest has been increasing in Shikonin, extracted from the naphthoquinone plant, particularly in determining its renal protective effect.

METHODS

In this study, we explored Shikonin's effects and potential mechanisms on a streptozotocin (STZ)-induced DN experimental model. An STZ-induced rat diabetic model was established, and the rats were treated with different doses of Shikonin (10/50 mg/kg) for 4 weeks. Blood, urine, and renal tissue samples were collected after the last administration. Renal tissues were examined to detect each group's physiologic, biochemical, histopathologic, and molecular changes.

RESULTS

The results showed that Shikonin administration could significantly alleviate the STZ-induced elevation of blood urea nitrogen, serum creatinine, urinary protein content, and renal pathologic injury. Furthermore, Shikonin significantly decreased oxidative stress, inflammation, and Toll-like receptor 4/myeloid differentiation primary response 88/nuclear factor-κB expression levels in DN kidney tissues. Shikonin showed a dose-dependent effect, with the best outcome at 50 mg/kg.

CONCLUSION

Shikonin could effectively alleviate DN-related nephropathy damage and reveal the underlying pharmacologic mechanism. Based on the results, a Shikonin combination can be used in clinical treatment.

Uropathogenic Escherichia coli (UPEC)-Associated Urinary Tract Infections: The Molecular Basis for Challenges to Effective Treatment

Urinary tract infections (UTIs) are among the most common bacterial infections, especially among women and older adults, leading to a significant global healthcare cost burden. Uropathogenic Escherichia coli (UPEC) are the most common cause and accounts for the majority of community-acquired UTIs. Infection by UPEC can cause discomfort, polyuria, and fever. More serious clinical consequences can result in urosepsis, kidney damage, and death. UPEC is a highly adaptive pathogen which presents significant treatment challenges rooted in a complex interplay of molecular factors that allow UPEC to evade host defences, persist within the urinary tract, and resist antibiotic therapy. This review discusses these factors, which include the key genes responsible for adhesion, toxin production, and iron acquisition. Additionally, it addresses antibiotic resistance mechanisms, including chromosomal gene mutations, antibiotic deactivating enzymes, drug efflux, and the role of mobile genetic elements in their dissemination. Furthermore, we provide a forward-looking analysis of emerging alternative therapies, such as phage therapy, nano-formulations, and interventions based on nanomaterials, as well as vaccines and strategies for immunomodulation. This review underscores the continued need for research into the molecular basis of pathogenesis and antimicrobial resistance in the treatment of UPEC, as well as the need for clinically guided treatment of UTIs, particularly in light of the rapid spread of multidrug resistance.

Kidney Damage in Long COVID: Studies in Experimental Mice

Signs and symptoms involving multiple organ systems which persist for weeks or months to years after the initial SARS-CoV-2 infection (also known as PASC or long COVID) are common complications of individuals with COVID-19. We recently reported pathophysiological changes in various organs post-acute infection of mice with mouse hepatitis virus-1 (MHV-1, a coronavirus) (7 days) and after long-term post-infection (12 months). One of the organs severely affected in this animal model is the kidney, which correlated well with human studies showing kidney injury post-SARS-CoV-2 infection. Our long-term post-infection pathological observation in kidneys includes the development of edema and inflammation of the renal parenchyma, severe acute tubular necrosis, and infiltration of macrophages and lymphocytes, in addition to changes observed in both acute and long-term post-infection, which include tubular epithelial cell degenerative changes, peritubular vessel congestion, proximal and distal tubular necrosis, hemorrhage in the interstitial tissue, and vacuolation of renal tubules. These findings strongly suggest the possible development of renal fibrosis, in particular in the long-term post-infection. Accordingly, we investigated whether the signaling system that is known to initiate the above-mentioned changes in kidneys in other conditions is also activated in long-term post-MHV-1 infection. We found increased TGF-β1, FGF23, NGAL, IL-18, HIF1-α, TLR2, YKL-40, and B2M mRNA levels in long-term post-MHV-1 infection, but not EGFR, TNFR1, BCL3, and WFDC2. However, only neutrophil gelatinase-associated lipocalin (NGAL) increased in acute infection (7 days). Immunoblot studies showed an elevation in protein levels of HIF1-α, TLR-2, and EGFR in long-term post-MHV-1 infection, while KIM-1 and MMP-7 protein levels are increased in acute infection. Treatment with a synthetic peptide, SPIKENET (SPK), which inhibits spike protein binding, reduced NGAL mRNA in acute infection, and decreased TGF-β1, BCL3 mRNA, EGFR, HIF1-α, and TLR-2 protein levels long-term post-MHV-1 infection. These findings suggest that fibrotic events may initiate early in SARS-CoV-2 infection, leading to pronounced kidney fibrosis in long COVID. Targeting these factors therapeutically may prevent acute or long-COVID-associated kidney complications.

Myrrh Essential Oil Mitigates Renal Ischemia/Reperfusion-Induced Injury

BACKGROUND

Ischemia/reperfusion (I/R)-induced renal injury is a common reason for kidney injury in clinical settings; therefore, continuous investigation of novel nephroprotective agents is crucial. Myrrh, the oleoresin exudates generated by the genus Commiphora, display numerous pharmacological actions. This study tried to assess the preventive effects of myrrh essential oil against I/R-induced renal damage.

METHODS

Rats were randomized into five groups. In the sham group, the animals were subjected to bilateral renal artery separation with no occlusion. In the sham + myrrh group; the rats were administered myrrh essential oil and then treated similarly to the sham group. Renal I/R group: the animals were challenged with renal I/R. In the myrrh + renal I/R groups, rats were administered 50 or 100 mg/kg of myrrh essential oil orally for three weeks before being confronted with I/R.

RESULTS

Serum levels of renal function tests and renal injury biomarkers, including NGAL, KIM-1, and CysC, were amplified in the renal I/R group. Animals that experienced renal I/R exhibited elevated lipid peroxidation (MDA); declined SOD, CAT, and GPx activity; declined GSH content; augmented TLR4/NFκB gene expression; and subsequent enhancement of inflammatory mediators (TNF-α, IFN-γ, IL-1β, and IL-6). Myrrh reduced renal function tests and injury biomarkers and amended renal histological alterations. Pretreatment with myrrh reduced MDA, elevated the antioxidant enzymes' activities and GSH content, and reduced the TLR4 and NFκB gene expression, leading to subsequent inflammation and apoptosis alleviation.

CONCLUSIONS

The outcomes of the present investigation established the protective effect of myrrh essential oil against renal I/R via pointing out the antioxidant, anti-inflammatory, and anti-apoptotic effects of myrrh.

Title: Bioinformatic Identification of Genes Involved in Diabetic Nephropathy Fibrosis and their Clinical Relevance

Tubulointerstitial fibrosis is an important pathological feature of diabetic nephropathy that is associated with impaired renal function. However, the mechanism by which fibrosis occurs in diabetic nephropathy is unclear. Differentially expressed genes were identified from transcriptome profiles of renal tissue from diabetic patients and unilateral ureteral obstruction mice and intersected to obtain genes that may be involved in diabetic fibrosis. Biological function analysis and protein-protein interaction network analysis were performed. ROC curve and Pearson correlation analysis between hub genes were performed and glomerular filtration rate estimated. Finally, the RNA levels of hub genes were measured using real-time PCR. A total of 283 genes were identified as potentially involved in diabetic nephropathy fibrosis. TYROBP, CTSS, LCP2, LUM and TLR7 were identified as aberrantly expressed hub genes. Immune cell infiltration analysis demonstrated higher numbers of cytotoxic lymphocytes, B lineage cells, monocyte lineage cells, myeloid dendritic cells, neutrophils, and fibroblasts in the diabetic nephropathy group. The areas under ROC curves for TYROBP, CTSS, LCP2, LUM and TLR7 were 0.9167, 0.9583, 0.9917, 0.93333, and 0.9583, respectively (P < 0.001), and their correlation coefficients with estimated glomerular filtration rate were - 0.8332, - 0.752, - 0.7875, - 0.7567, and - 0.7136, respectively (P < 0.001). The RNA levels of TYROBP, CTSS, LUM and TLR7 were upregulated in high-glucose-treated human renal tubular epithelial cells (P < 0.005). Our study identified TYROBP, CTSS, LCP2, LUM and TLR7 as potentially involved in diabetic nephropathy fibrosis. Furthermore, TYROBP, CTSS, LUM and TLR7 may be associated with epithelial-mesenchymal transition of tubular epithelial cells.

The Role of Gut Microbiota and Trimethylamine N-oxide in Cardiovascular Diseases

Changes in the intestinal flora and its metabolites have been associated with cardiovascular disease (CVD). Short-chain fatty acids, bile acids, and especially trimethylamine N-oxide (TMAO), an endothelial toxic factor produced by gut microbiota from phosphatidylcholine in meat, have been identified to be closely related to endothelial cell dysfunction as well as tightly affiliated with CVD, the two main types being coronary artery disease (CAD) and coronary microvascular disease (CMVD). We discuss how changes in the gut flora and the metabolite TMAO contribute to the development of CAD and CMVD. The above insight might serve as a stepping stone for novel CAD and CMVD diagnostics and therapies centered on microbiota.

The Importance of Toll-like Receptor 9 Expression on Monocytes and Dendritic Cells in the Context of Epstein–Barr Virus Infection in the Immunopathogenesis of Primary Glomerulonephritis

Toll-like receptor 9 (TLR9) is activated by unmethylated cytosine-phosphate-guanosine (CpG) dinucleotides found in the genomes of pathogens such as Epstein–Barr virus (EBV). The aim of this study was to determine the role of TLR9 in the immunopathogenesis of IgA nephropathy (IgAN) and membranoproliferative glomerulonephritis (MPGN) in the context of Epstein–Barr virus (EBV) infection. For this purpose, the frequency of TLR9-positive monocytes and dendritic cells (DCs, i.e., BDCA-1; myeloid dendritic cells, and BDCA-2; plasmocytoid dendritic cells) was studied, and a quantitative analysis of the concentration of TLR9 in the serum of patients diagnosed with IgAN and MPGN was undertaken. Higher frequencies of TLR9-positive DCs and monocytes in IgAN and MPGN patients were observed as compared with the control group. Patients diagnosed with GN exhibited a higher percentage of BDCA-1+CD19− and BDCA-2+CD123+ DCs than patients in the control group. Moreover, serum TLR9 concentration was shown to be significantly correlated with EBV DNA copy number/µg DNA, IgG, IgM, serum albumin, total protein in 24-h urine collection test and the frequency of BDCA-2+CD123+ DCs in peripheral blood. Our findings confirm that TLR9 may be involved in the development of IgAN and MPGN.

A Glimpse of Inflammation and Anti-Inflammation Therapy in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a common complication of diabetes mellitus and a major cause of end-stage kidney disease (ESKD). The pathogenesis of DKD is very complex and not completely understood. Recently, accumulated evidence from in vitro and in vivo studies has demonstrated that inflammation plays an important role in the pathogenesis and the development of DKD. It has been well known that a variety of pro-inflammatory cytokines and related signaling pathways are involved in the procession of DKD. Additionally, some anti-hyperglycemic agents and mineralocorticoid receptor antagonists (MRAs) that are effective in alleviating the progression of DKD have anti-inflammatory properties, which might have beneficial effects on delaying the progression of DKD. However, there is currently a lack of systematic overviews. In this review, we focus on the novel pro-inflammatory signaling pathways in the development of DKD, including the nuclear factor kappa B (NF-κB) signaling pathway, toll-like receptors (TLRs) and myeloid differentiation primary response 88 (TLRs/MyD88) signaling pathway, adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling pathways, inflammasome activation, mitochondrial DNA (mtDNA) release as well as hypoxia-inducible factor-1(HIF-1) signaling pathway. We also discuss the related anti-inflammation mechanisms of metformin, finerenone, sodium-dependent glucose transporters 2 (SGLT2) inhibitors, Dipeptidyl peptidase-4 (DPP-4) inhibitors, Glucagon-like peptide-1 (GLP-1) receptor agonist and traditional Chinese medicines (TCM).

RIP3 Translocation into Mitochondria Promotes Mitofilin Degradation to Increase Inflammation and Kidney Injury after Renal Ischemia-Reperfusion

The receptor-interacting protein kinase 3 (RIP3) has been reported to regulate programmed necrosis-necroptosis forms of cell death with important functions in inflammation. We investigated whether RIP3 translocates into mitochondria in response to renal ischemia-reperfusion (I/R) to interact with inner mitochondrial protein (Mitofilin) and promote mtDNA release into the cytosol. We found that release of mtDNA activates the cGAS-STING pathway, leading to increased nuclear transcription of pro-inflammatory markers that exacerbate renal I/R injury. Monolateral C57/6N and RIP3^-/- mice kidneys were subjected to 60 min of ischemia followed by either 12, 24, or 48 h of reperfusion. In WT mice, we found that renal I/R injury increased RIP3 levels, as well as its translocation into mitochondria. We observed that RIP3 interacts with Mitofilin, likely promoting its degradation, resulting in increased mitochondria damage and mtDNA release, activation of the cGAS-STING-p65 pathway, and increased transcription of pro-inflammatory markers. All of these effects observed in WT mice were decreased in RIP3^-/- mice. In HK-2, RIP3 overexpression or Mitofilin knockdown increased cell death by activating the cGAS-STING-p65 pathway. Together, this study point to an important role of the RIP3-Mitofilin axis in the initiation and development of renal I/R injury.

Long Noncoding RNA MEG3-205/Let-7a/MyD88 Axis Promotes Renal Inflammation and Fibrosis in Diabetic Nephropathy

AIM

The aim of this study was to investigate the role and mechanism of long noncoding RNA (lncRNA) maternally expressed gene 3 (MEG3)-205 in renal inflammation and fibrosis in diabetic nephropathy (DN).

MATERIALS AND METHODS

lncRNA microarray profiling was used to examine differentially expressed lncRNAs of kidney tissues in db/db mice compared to db/m mice. Mouse mesangial cells (mMCs) were cultured in vitro with advanced glycation end products (AGEs) via transfection with lncRNA MEG3-205 siRNAs or plasmids. The role of lncRNA MEG3-205 in vivo was examined in db/db mice treated with long-acting lncRNA MEG3-205 siRNA. The interaction between lncRNA MEG3-205 and let-7a was investigated using luciferase assay and RNA immunoprecipitation assay.

RESULTS

lncRNA MEG3-205 was markedly upregulated in renal tissues of db/db mice, DN patients, and AGEs-treated mesangial cells. Overexpression of lncRNA MEG3-205 promoted the secretion of pro-inflammatory cytokines and synthesis of extracellular matrix proteins in mesangial cells. Both lncRNA MEG3-205 and myeloid differentiation primary-response protein 88 (MyD88) could bind to let-7a, and lncRNA MEG3-205 overexpression can significantly rescue the silencing effect of let-7a on MyD88 protein expression in mMCs. Mechanistically, we identified that lncRNA MEG3-205 could act as a competing endogenous RNA by binding with let-7a and thus regulate MyD88. Knockdown of lncRNA MEG3-205 alleviated albuminuria and attenuated renal inflammation and fibrosis in db/db mice.

CONCLUSION

These findings indicated an important role of the lncRNA MEG3-205/let-7a/MyD88 axis in regulating renal inflammation and fibrosis in DN. Targeting lncRNA MEG3-205 might present a promising therapeutic strategy for DN.

Sex Differences in TLR4 Expression in SHR Do Not Contribute to Sex Differences in Blood Pressure or the Renal T cell Profile

Hypertension is a primary risk factor for the development of cardiovascular disease. Mechanisms controlling blood pressure (BP) in men and women are still being investigated, however, there is increasing evidence supporting a role for the innate immune system. Specifically, Toll-like receptors (TLR), and TLR4 in particular, have been implicated in the development of hypertension in male spontaneously hypertensive rats (SHR). Despite established sex differences in BP control and inflammatory markers in hypertensive males and females, little is known regarding the role of TLR4 in hypertension in females. Our hypotheses were that male SHR have greater TLR4 expression compared to females, and that sex differences in TLR4 contribute to sex differences in BP and the T cell profile. To test these hypotheses, initial studies measured renal TLR4 protein expression in 13-week old male and female SHR. Additional SHR were implanted with telemetry devices and randomized to treatment with either IgG or TLR4 neutralizing antibodies. Untreated control male SHR have greater TLR4 protein expression in the kidney compared to females. However, treatment with TLR4 neutralizing antibody for 2 weeks did not significantly alter BP in either male or female SHR. Interestingly, neutralization of TLR4 increased renal CD3⁺ T cells in female SHR, with no alteration in CD4⁺ T cells or CD8⁺ T cells in either sex. Taken together, our data indicates that although male SHR have greater renal TLR4 expression than females, TLR4 does not contribute to the higher BP and more pro-inflammatory renal T cell prolife in males vs. females.

Anti-Oxidant and Anti-Inflammatory Effects of Lipopolysaccharide from Rhodobacter sphaeroides against Ethanol-Induced Liver and Kidney Toxicity in Experimental Rats

This study aimed to investigate the protective effects of lipopolysaccharide from Rhodobacter sphaeroides (LPS-RS) against ethanol-induced hepatotoxicity and nephrotoxicity in experimental rats. The study involved an intact control group, LPS-RS group, two groups were given ethanol (3 and 5 g/kg/day) for 28 days, and two other groups (LPS-RS + 3 g/kg ethanol) and (LPS-RS + 5 g/kg ethanol) received a daily dose of LPS-RS (800 μg/kg) before ethanol. Ethanol significantly increased the expression of nuclear factor kappa B (NF-κB) and levels of malondialdehyde (MDA), tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in the liver tissue and decreased anti-oxidant enzymes. Hepcidin expression was downregulated in the liver, with increased serum levels of ferritin and iron. Prior-administration of LPS-RS alleviated the increase in oxidative stress and inflammatory markers, and preserved iron homeostasis markers. In the kidney, administration of ethanol caused significant increase in the expression of NF-κB and the levels of TNF-α and kidney injury markers; whereas LPS-RS + ethanol groups had significantly lower levels of those parameters. In conclusion; this study reports anti-oxidant, anti-inflammatory and iron homeostasis regulatory effects of the toll-like receptor 4 (TLR4) antagonist LPS-RS against ethanol induced toxicity in both the liver and the kidney of experimental rats.

Crocetin attenuating Urinary tract Infection and adherence of uropathogenic E. coli in NRK-52E cells via an inflammatory pathway

BACKGROUND AND OBJECTIVE

Urinary tract infections (UTI) are commonly treated with broad-spectrum antibiotics, but treatment has limitation due to causes of nephrotoxicity in uroepithelial cells. Recently, the researcher focuses their research on alternative therapy for the treatment of UTI. This study evaluated the anti-infectious effect of crocetin against adherence of pathogenic [2-¹⁴ C]-acetate labeled Escherichia coli (MTCC-729) to rat proximal renal tubular cells (NRK-52E cells) and explores the possible mechanism of action.

MATERIALS AND METHODS

In vitro cytotoxicity and radio acetate labeled tests were performed on NRK-52E cells. The rats were divided into five different groups as follows: normal control (NC), disease control (DC), and various doses of crocetin (1.25, 2.5, and 5 mg/kg) treated group rats. White blood cells in blood, urine, and bacterial colony counts were estimated at regular intervals. Pro-inflammatory cytokines, such as interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), interleukin-10 (IL-10), and interleukin-8 (IL-8), were also estimated. In the current study, we estimated the mRNA expression of toll-like receptor-4 (TLR-4) and toll-like receptor-2 (TLR-2) in the renal and bladder tissues.

RESULTS

Crocetin significantly (p < .05) inhibited the adherence of E. Coli in NRK-52E cells. Crocetin suppresses the lipid peroxidation (LPO) 42% in cells treated with H₂ O₂ cells without crocetin. The white blood cells (WBC) count in blood and urine were augmented and crocetin treatment significantly (p < .05) reduced the WBC in urine and blood. The pro-inflammatory cytokines, such as IL-6, MCP-1, IL-10, and IL-8, significantly (p < .05) increased in the DC group and crocetin significantly (p < .05) reduced the pro-inflammatory cytokines. Dose-dependent treatment of crocetin significantly reduced the mRNA expression of TLR2 and TLR4 in the renal and bladder tissues.

CONCLUSION

Crocetin considerably reduced the bacterial adherence to NRK-52E cells, attenuated the H₂ O₂ induced toxicity in NRK-52E cells and also improved the renal tubular function, and reduced the inflammatory response via altering the inflammatory and antioxidant markers.

PRACTICAL APPLICATION

As we all know that urinary tract infection is the most common disease worldwide. In this study, we scrutinized the protective effect of crocetin against urinary tract infection. Crocetin treatment considerably reduced the zone of inhibition and improved radioactivity. Crocetin significantly reduced the levels of cytokines and inflammatory mediators. Crocetin can be used as a protective drug in the treatment of urinary tract infections.

Probiotics and Trained Immunity

The characteristics of innate immunity have recently been investigated in depth in several research articles, and original findings suggest that innate immunity also has a memory capacity, which has been named “trained immunity”. This notion has revolutionized our knowledge of the innate immune response. Thus, stimulation of trained immunity represents a therapeutic alternative that is worth exploring. In this context, probiotics, live microorganisms which when administered in adequate amounts confer a health benefit on the host, represent attractive candidates for the stimulation of trained immunity; however, although numerous studies have documented the beneficial proprieties of these microorganisms, their mechanisms of action are not yet fully understood. In this review, we propose to explore the putative connection between probiotics and stimulation of trained immunity.