C/EBP-beta modulates transcription of tubulointerstitial nephritis antigen in obstructive uropathy

Genetic determinants of renal scarring in children with febrile UTI

BACKGROUND

Febrile urinary tract infections (UTIs) are among the most severe bacterial infections in infants, in which a subset of patients develops complications. Identifying infants at risk of recurrent infections or kidney damage based on clinical signs is challenging. Previous observations suggest that genetic factors influence UTI outcomes and could serve as predictors of disease severity. In this study, we conducted a nationwide survey of infant genotypes to develop a strategy for infection management based on individual genetic risk. Our aims were to identify genetic susceptibility variants for renal scarring (RS) and genetic host factors predisposing to dilating vesicoureteral reflux (VUR) and recurrent UTIs.

METHODS

To assess genetic susceptibility, we collected and analyzed DNA from blood using exome genotyping. Disease-associated genetic variants were identified through bioinformatics analysis, including allelic frequency tests and odds ratio calculations. Kidney involvement was defined using dimercaptosuccinic acid (DMSA) scintigraphy.

RESULTS

In this investigation, a cohort comprising 1087 infants presenting with their first episode of febrile UTI was included. Among this cohort, a subset of 137 infants who underwent DMSA scanning was subjected to gene association analysis. Remarkable genetic distinctions were observed between patients with RS and those exhibiting resolved kidney involvement. Notably, the genetic signature indicative of renal scarring prominently featured mitochondrial genes.

CONCLUSIONS

In this nationwide study of genetic susceptibility to RS after febrile UTIs in infancy, we identified a profile dominated by mitochondrial polymorphisms. This profile can serve as a predictor of future complications, including RS and recurrent UTIs.

Tryptophan Metabolites Target Transmembrane and Immunoglobulin Domain-Containing 1 Signaling to Augment Renal Tubular Injury

Chronic kidney disease (CKD) is characterized by the accumulation of uremic toxins and renal tubular damage. Tryptophan-derived uremic toxins [indoxyl sulfate (IS) and kynurenine (Kyn)] are well-characterized tubulotoxins. Emerging evidence suggests that transmembrane and immunoglobulin domain-containing 1 (TMIGD1) protects tubular cells and promotes survival. However, the direct molecular mechanism(s) underlying how these two opposing pathways crosstalk remains unknown. We posited that IS and Kyn mediate tubular toxicity through TMIGD1 and the loss of TMIGD1 augments tubular injury. Results from the current study showed that IS and Kyn suppressed TMIGD1 transcription in tubular cells in a dose-dependent manner. The wild-type CCAAT enhancer-binding protein β (C/EBPβ) enhanced, whereas a dominant-negative C/EBPβ suppressed, TMIGD1 promoter activity. IS down-regulated C/EBPβ in primary human renal tubular cells. The adenine-induced CKD, unilateral ureteric obstruction, and deoxycorticosterone acetate salt unilateral nephrectomy models showed reduced TMIGD1 expression in the renal tubules, which correlated with C/EBPβ expression. C/EBPβ levels negatively correlated with the IS and Kyn levels. Inactivation of TMIGD1 in mice significantly lowered acetylated tubulin, decreased tubular cell proliferation, caused severe tubular damage, and worsened renal function. Thus, the current results demonstrate that TMIGD1 protects renal tubular cells from renal injury in different models of CKD and uncovers a novel mechanism of tubulotoxicity of tryptophan-based uremic toxins.

FOXD1 is required for 3D patterning of the kidney interstitial matrix

BACKGROUND

The interstitial extracellular matrix (ECM) is comprised of proteins and glycosaminoglycans and provides structural and biochemical information during development. Our previous work revealed the presence of transient ECM-based structures in the interstitial matrix of developing kidneys. Stromal cells are the main contributors to interstitial ECM synthesis, and the transcription factor Forkhead Box D1 (Foxd1) is critical for stromal cell function. To investigate the role of Foxd1 in interstitial ECM patterning, we combined 3D imaging and proteomics to explore how the matrix changes in the murine developing kidney when Foxd1 is knocked out.

RESULTS

We found that COL26A1, FBN2, EMILIN1, and TNC, interstitial ECM proteins that are transiently upregulated during development, had a similar distribution perinatally but then diverged in patterning in the adult. Abnormally clustered cortical vertical fibers and fused glomeruli were observed when Foxd1 was knocked out. The changes in the interstitial ECM of Foxd1 knockout kidneys corresponded to disrupted Foxd1+ cell patterning but did not precede branching dysmorphogenesis.

CONCLUSIONS

The transient ECM networks affected by Foxd1 knockout may provide support for later-stage nephrogenic structures.

Genome-wide association study of dermatophytosis in the UK Biobank cohort

BACKGROUND

Analyses of the hereditary propensity to dermatophytosis have revealed several proven genetic relationships. They include CARD9 deficiency, HLA-DR4 and HLA-DR8 type and genes encoding interleukin-22, defensin 2 and 4, and genetic defects in dectin-1, which increased the prevalence of dermatophytosis in families and were involved in the inheritance of susceptibility in their members.

METHODS

To further investigate the genetic basis of dermatophytosis, we performed a genome-wide association study (GWAS) of the UK Biobank cohort. To identify cases of dermatophytosis, we used ICD10 code B35, which covers Tinea barbae, Tinea capitis, Tinea unguium, Tinea manuum, Tinea pedis, Tinea corporis, Tinea imbricata, Tinea cruris, other dermatophytoses and dermatophytosis, unspecified. Data processing was performed on Minerva, a Linux mainframe with Centos 7.6, at the Icahn School of Medicine at Mount Sinai. We used PLINK, a whole-genome association analysis toolset, to analyse the UKB chromosome files and the UK Biobank Data Parser (ukbb parser), a python-based package that allows easy interfacing with the large UK Biobank dataset. We used LocusZoom for the Manhattan and q-q plots. Other statistical analyses were done with R and SPSS 25.

RESULTS

Genome-wide association study (GWAS) and meta-analysis association statistics highlighted one susceptibility locus, Tubulointerstitial Nephritis Antigen (TINAG), with genome-wide significance for dermatophytosis. The top SNP was rs16885197, a missense variant within TINAG, position chr6:54308557, alleles A > G, minor allele frequency (MAF) 0.014. Multivariate logistic regression indicated that the minor G allele increased odds ratio of dermatophytosis by 7.8. Carrying two G alleles raised dermatophytosis odds ratio by a factor of 14.

CONCLUSION

More research into genetic and other predisposing factors for dermatophytosis is critical because of the implications for prophylaxis and therapy. It might be possible to prevent infection and recurrence by identifying people who are vulnerable to chronic dermatophytosis. Identifying high-risk families would enable their members to be educated about the dangers of fungal diseases. New therapeutic techniques to target altered hormonal and immune response pathways might be created. TINAG is a prospective target that should be investigated, based on the findings of this article.

CCAAT/Enhancer-Binding Proteins in Fibrosis: Complex Roles Beyond Conventional Understanding

CCAAT/enhancer-binding proteins (C/EBPs) are a family of at least six identified transcription factors that contain a highly conserved basic leucine zipper domain and interact selectively with duplex DNA to regulate target gene expression. C/EBPs play important roles in various physiological processes, and their abnormal function can lead to various diseases. Recently, accumulating evidence has demonstrated that aberrant C/EBP expression or activity is closely associated with the onset and progression of fibrosis in several organs and tissues. During fibrosis, various C/EBPs can exert distinct functions in the same organ, while the same C/EBP can exert distinct functions in different organs. Modulating C/EBP expression or activity could regulate various molecular processes to alleviate fibrosis in multiple organs; therefore, novel C/EBPs-based therapeutic methods for treating fibrosis have attracted considerable attention. In this review, we will explore the features of C/EBPs and their critical functions in fibrosis in order to highlight new avenues for the development of novel therapies targeting C/EBPs.

Epac activation ameliorates tubulointerstitial inflammation in diabetic nephropathy

Tubulointerstitial inflammation plays an important role in the progression of diabetic nephropathy (DN), and tubular epithelial cells (TECs) are crucial promoters of the inflammatory cascade. Exchange protein activated by cAMP (Epac) has been shown to suppress the angiotensin II (Ang-II)-induced release of inflammatory cytokines in tubular cells. However, the role of Epac in TEC-mediated tubulointerstitial inflammation in DN remains unknown. We found that administering the Epac agonist 8-pCPT-2'-O-Me-cAMP (8-O-cAMP) to db/db mice inhibited tubulointerstitial inflammation characterized by macrophage infiltration and increased inflammatory cytokine release and consequently alleviated tubulointerstitial fibrosis in the kidney. Furthermore, 8-O-cAMP administration restored CCAAT/enhancer binding protein β (C/EBP-β) expression and further upregulated the expression of Suppressor of cytokine signaling 3 (SOCS3), while inhibiting p-STAT3, MCP-1, IL-6, and TNF-α expression in the kidney cortex in db/db mice. And in vitro study showed that macrophage migration and MCP-1 expression induced by high glucose (HG, 30 mM) were notably reduced by 8-O-cAMP in human renal proximal tubule epithelial (HK-2) cells. In addition, 8-O-cAMP treatment restored C/EBP-β expression in HK-2 cells and promoted C/EBP-β translocation to the nucleus, where it transcriptionally upregulated SOCS3 expression, subsequently inhibiting STAT3 phosphorylation. Under HG conditions, siRNA-mediated knockdown of C/EBP-β or SOCS3 in HK-2 cells partially blocked the inhibitory effect of Epac activation on the release of MCP-1. In contrast, SOCS3 overexpression inhibited HG-induced activation of STAT3 and MCP-1 expression in HK-2 cells. These findings indicate that Epac activation via 8-O-cAMP ameliorates tubulointerstitial inflammation in DN through the C/EBP-β/SOCS3/STAT3 pathway.

Collecting Duct-Specific CR6-Interacting Factor-1-Deletion Aggravates Renal Inflammation and Fibrosis Induced by Unilateral Ureteral Obstruction

Although inflammation and fibrosis, which are key mechanisms of chronic kidney disease, are associated with mitochondrial damage, little is known about the effects of mitochondrial damage on the collecting duct in renal inflammation and fibrosis. To generate collecting duct-specific mitochondrial injury mouse models, CR6-interacting factor-1 (CRIF1) flox/flox mice were bred with Hoxb7-Cre mice. We evaluated the phenotype of these mice. To evaluate the effects on unilateral ureteral obstruction (UUO)-induced renal injury, we divided the mice into the following four groups: a CRIF1flox/flox (wild-type (WT)) group, a CRIF1flox/flox-Hob7 Cre (CRIF1-KO) group, a WT-UUO group, and a CRIF1-KO UUO group. We evaluated the blood and urine chemistries, inflammatory and fibrosis markers, light microscopy, and electron microscopy of the kidneys. The inhibition of Crif1 mRNA in mIMCD cells reduced oxygen consumption and membrane potential. No significant differences in blood and urine chemistries were observed between WT and CRIF1-KO mice. In UUO mice, monocyte chemoattractant protein-1 and osteopontin expression, number of F4/80 positive cells, transforming growth factor-β and α-smooth muscle actin staining, and Masson's trichrome staining were significantly higher in the kidneys of CRIF1-KO mice compared with the kidneys of WT mice. In sham mice, urinary 8-hydroxydeoxyguanosine (8-OHDG) was higher in CRIF1-KO mice than in WT mice. Moreover, CRIF1-KO sham mice had increased 8-OHDG-positive cell recruitment compared with WT-sham mice. CRIF1-KO-UUO kidneys had increased recruitment of 8-OHDG-positive cells compared with WT-UUO kidneys. In conclusion, collecting duct-specific mitochondrial injury increased oxidative stress. Oxidative stress associated with mitochondrial damage may aggravate UUO-induced renal injury.

IRF-1 promotes renal fibrosis by downregulation of Klotho

Although the key role of renal fibrosis in the progression of chronic kidney disease (CKD) is well known, the causes of renal fibrosis are not fully clarified. In this study, interferon regulatory factor 1 (IRF-1), a mammalian transcription factor, was highly expressed in fibrotic kidney of CKD patients. Concordantly, the expression level of IRF-1 was significantly elevated in the kidney of unilateral ureteral obstruction (UUO) and Adriamycin nephropathy (ADR) mice. In tubular epithelial cells, overexpression of IRF-1 could induce profibrotic markers expression, which accompanied by dramatic downregulation of Klotho, an important inhibitor of renal fibrosis. Luciferase reporter analysis and ChIP assay revealed that IRF-1 repressed Klotho expression by downregulation of C/EBP-β, which regulates Klotho gene transcription via directly binding to its promoter. Further investigation showed that tumor necrosis factor-alpha may be an important inducement for the increase of IRF-1 in tubular epithelial cells after UUO and genetic deletion of IRF-1 attenuated renal fibrosis in UUO mice. Hence, these findings demonstrate that IRF-1 contributes to the pathogenesis of renal fibrosis by downregulation of Klotho, and suppresses IRF-1 may be a potential therapeutic target for CKD.

Transplantation of Amniotic Fluid-Derived Stem Cells Preconditioned with Glial Cell Line-Derived Neurotrophic Factor Gene Alleviates Renal Fibrosis

Amniotic fluid-derived stem cells (AFSCs), which exhibit both embryonic and mesenchymal stem cell characteristics, have been shown to mitigate the degree of renal interstitial fibrosis. The aim of the present study was to determine whether transplantation of glial cell line-derived neurotrophic factor (GDNF)–modified AFSCs is more useful than transplantation of unmodified AFSCs for the treatment of renal interstitial fibrosis. Mice were randomly assigned to a sham-operation group (sham), a unilateral ureteral obstruction (UUO)-saline solution group (UUO), an AFSC transplantation group (AFSC) and a GDNF-modified AFSC transplantation group (GDNF-AFSC) and sacrificed at days 3 and 7 post-surgery (six in each group). We showed that GDNF-AFSCs noticeably suppressed oxidative stress and inflammation; additionally, GDNF-AFSCs positively regulated peritubular capillaries (PTCs), vascular endothelial growth factor (VEGF), hypoxia inducible factor-1α (HIF-1α), and transforming growth factor-β1 (TGF-β1) protein levels. Transmission electron microscopy (TEM) revealed that mitochondrial injury induced by the UUO model was significantly ameliorated after the mice were treated with GDNF-AFSCs. Therefore, we determined that GDNF gene promotes the abilities of AFSCs to inhibit inflammatory and oxidative stress effects, repair renal microvessels, relieve tissue hypoxia and mitochondrial damage, and, ultimately, alleviate renal interstitial fibrosis.

Cardioprotection of Sheng Mai Yin a classic formula on adriamycin induced myocardial injury in Wistar rats

BACKGROUND

Sheng Mai Yin (SMY), a well-known Chinese herbal medicine, is widely used to treat cardiac diseases characterized by the deficiency of Qi and Yin syndrome in China. SMY-based treatment has been derived from Traditional Chinese Medicine (TCM), officially recorded in the Chinese Pharmacopoeia.

PURPOSE

We aimed to clarify whether SMY attenuates myocardial injury induced by adriamycin in Wistar rats with chronic heart failure (CHF).

METHODS

To quantify ginsenoside Rg1, ophiopogonin D, ophiopogonin D', schisandrin by HPLC. To establish CHF animal model, adriamycin was intraperitoneally injected in Wistar rats for 7 weeks at a dose of 2 mg/kg body weight. Overall, 180 rats were randomly assigned to six groups: control, CHF model, captopril (positive control), high dose (HSMY), medium dose (MSMY), and low dose (LSMY). Experimental rats were fed 0.625 mg/kg captopril and 90 mg/kg, 45 mg/kg, and 22.5 mg/kg SMY, respectively, over 7 weeks. The inflammatory cytokines TNF-α and IL-6 were measured using ELISA. Matrix metalloproteinases (MMPs) were identified using immunohistochemistry (IHC). Both IHC and RT-PCR were used for quantification of COL-IV expression levels in the heart tissues. Scanning electron microscopy (SEM) was used for the visualization of myocardium morphology.

RESULTS

The concentration of ginsenoside Rg1, ophiopogonin D, ophiopogonin D' and schisandrin in SMY was found to be 25.63 ± 3.42 mg, 11.00 ± 1.17 mg, 7.02 ± 0.51 mg, and 25.31 ± 4.28 mg per gram of SMY, respectively. Compared with CHF model group, TNF-α levels were significantly lower (p < .01) in the four drug-administered groups. Moreover, except in the SYM low dose group, IL-6 levels in the other 3 drug-administered groups were also significantly reduced (p < .01). COL-IV expression was also significantly reduced on treatment with high SYM dose (p < .05). IHC results confirmed that SMY and captopril significantly reduced MMPs expression in the heart.

CONCLUSION

SMY could control or slow CHF progression by suppressing pathological changes in the myocardium in CHF models. This could be attributed at least partly to the downregulation of IL-6 and TNF-α and inhibition of overexpression of MMPs and COL-IV, which significantly relieved the cardiac-linked pathologies, decreased the risk of myocardial fibrosis, and inhibited cardiac remodeling. These findings suggested that SMY and captopril have similar efficacy for the treatment of adriamycin-induced myocardial injury. In addition, Chinese herbal preparation SMY may play a role in the treatment of cardiac diseases.

Evaluating the Oxidative Stress in Renal Diseases: What Is the Role for S-Glutathionylation?

SIGNIFICANCE

Reactive oxygen species (ROS) have long been considered as toxic derivatives of aerobic metabolism displaying a harmful effect to living cells. Deregulation of redox homeostasis and production of excessive free radicals may contribute to the pathogenesis of kidney diseases. In line, oxidative stress increases in patients with renal dysfunctions due to a general increase of ROS paralleled by impaired antioxidant ability.

RECENT ADVANCES

Emerging evidence revealed that physiologically, ROS can act as signaling molecules interplaying with several transduction pathways such as proliferation, differentiation, and apoptosis. ROS can exert signaling functions by modulating, at different layers, protein oxidation since proteins have "cysteine switches" that can be reversibly reduced or oxidized, supporting the dynamic signaling regulation function. In this scenario, S-glutathionylation is a posttranslational modification involved in oxidative cellular response.

CRITICAL ISSUES

Although it is widely accepted that renal dysfunctions are often associated with altered redox signaling, the relative role of S-glutathionylation on the pathogenesis of specific renal diseases remains unclear and needs further investigations. In this review, we discuss the impact of ROS in renal health and diseases and the role of selective S-glutathionylation proteins potentially relevant to renal physiology.

FUTURE DIRECTIONS

The paucity of studies linking the reversible protein glutathionylation with specific renal disorders remains unmet. The growing number of S-glutathionylated proteins indicates that this is a fascinating area of research. In this respect, further studies on the association of reversible glutathionylation with renal diseases, characterized by oxidative stress, may be useful to develop new pharmacological molecules targeting protein S-glutathionylation. Antioxid. Redox Signal. 25, 147-164.

OVOL guides the epithelial-hybrid-mesenchymal transition

Metastasis involves multiple cycles of Epithelial-to-Mesenchymal Transition (EMT) and its reverse-MET. Cells can also undergo partial transitions to attain a hybrid epithelial/mesenchymal (E/M) phenotype that has maximum cellular plasticity and allows migration of Circulating Tumor Cells (CTCs) as a cluster. Hence, deciphering the molecular players helping to maintain the hybrid E/M phenotype may inform anti-metastasis strategies. Here, we devised a mechanism-based mathematical model to couple the transcription factor OVOL with the core EMT regulatory network miR-200/ZEB that acts as a three-way switch between the E, E/M and M phenotypes. We show that OVOL can modulate cellular plasticity in multiple ways - restricting EMT, driving MET, expanding the existence of the hybrid E/M phenotype and turning both EMT and MET into two-step processes. Our theoretical framework explains the differences between the observed effects of OVOL in breast and prostate cancer, and provides a platform for investigating additional signals during metastasis.

Disruption of renal tubular mitochondrial quality control by Myo-inositol oxygenase in diabetic kidney disease

Diabetic kidney disease (DKD) is associated with oxidative stress and mitochondrial injury. Myo-inositol oxygenase (MIOX), a tubular-specific enzyme, modulates redox imbalance and apoptosis in tubular cells in diabetes, but these mechanisms remain unclear. We investigated the role of MIOX in perturbation of mitochondrial quality control, including mitochondrial dynamics and autophagy/mitophagy, under high-glucose (HG) ambience or a diabetic state. HK-2 or LLC-PK1 cells subjected to HG exhibited an upregulation of MIOX accompanied by mitochondrial fragmentation and depolarization, inhibition of autophagy/mitophagy, and altered expression of mitochondrial dynamic and mitophagic proteins. Furthermore, dysfunctional mitochondria accumulated in the cytoplasm, which coincided with increased reactive oxygen species generation, Bax activation, cytochrome C release, and apoptosis. Overexpression of MIOX in LLC-PK1 cells enhanced the effects of HG, whereas MIOX siRNA or d-glucarate, an inhibitor of MIOX, partially reversed these perturbations. Moreover, decreasing the expression of MIOX under HG ambience increased PTEN-induced putative kinase 1 expression and the dependent mitofusin-2-Parkin interaction. In tubules of diabetic mice, increased MIOX expression and mitochondrial fragmentation and defective autophagy were observed. Dietary supplementation of d-glucarate in diabetic mice decreased MIOX expression, attenuated tubular damage, and improved renal functions. Notably, d-glucarate administration also partially attenuated mitochondrial fragmentation, oxidative stress, and apoptosis and restored autophagy/mitophagy in the tubular cells of these mice. These results suggest a novel mechanism linking MIOX to impaired mitochondrial quality control during tubular injury in the pathogenesis of DKD and suggest d-glucarate as a potential therapeutic agent for the amelioration of DKD.

Rotenone remarkably attenuates oxidative stress, inflammation, and fibrosis in chronic obstructive uropathy

Mitochondrial abnormality has been shown in many kidney disease models. However, its role in the pathogenesis of chronic kidney diseases (CKDs) is still uncertain. In present study, a mitochondrial complex I inhibitor rotenone was applied to the mice subjected to unilateral ureteral obstruction (UUO). Following 7-days rotenone treatment, a remarkable attenuation of tubular injury was detected by PAS staining. In line with the improvement of kidney morphology, rotenone remarkably blunted fibrotic response as shown by downregulation of fibronectin (FN), plasminogen activator inhibitor-1 (PAI-1), collagen I, collagen III, and α-SMA, paralleled with a substantial decrease of TGF-β₁. Meanwhile, the oxidative stress markers thiobarbituric acid-reactive substances (TBARS) and heme oxygenase 1 (HO-1) and inflammatory markers TNF-α, IL-1β, and ICAM-1 were markedly decreased. More importantly, the reduction of mitochondrial DNA copy number and mitochondrial NADH dehydrogenase subunit 1 (mtND1) expression in obstructed kidneys was moderately but significantly restored by rotenone, suggesting an amelioration of mitochondrial injury. Collectively, mitochondrial complex I inhibitor rotenone protected kidneys against obstructive injury possibly via inhibition of mitochondrial oxidative stress, inflammation, and fibrosis, suggesting an important role of mitochondrial dysfunction in the pathogenesis of obstructive kidney disease.

LIM homeobox transcription factor 1B expression affects renal interstitial fibrosis and apoptosis in unilateral ureteral obstructed rats

LIM homeobox transcription factor 1B (LMX1B) is a transcription factor of the LIM homeodomain type and has been implicated in the development of diverse structures such as limbs, kidneys, eyes, and the brain. Furthermore, LMX1B has been implicated in nail-patella syndrome, which is predominantly characterized by malformation of limbs and nails, and in 30% of patients, nephropathy, including renal fibrosis, is observed. Since no reports were available that studied the link between LMX1B expression and renal interstitial fibrosis, we explored if LMX1B affects typical markers of fibrosis, e.g., extracellular matrix components, profibrotic factors, and apoptosis as the final detrimental consequence. We recently showed that LMX1B acts as a negative regulator of transforming growth factor-βl, collagen type III, fibronectin, cleaved caspase-3, and the cell apoptosis rate in a renal tubular epithelial cell system under hypoxic conditions. Here, we confirmed these results in unilateral ureteral obstructed rats. Furthermore, LMX1B was distinctly expressed throughout the glomerulus and tubule lining, including epithelial cells. Knockdown of LMX1B aggravated the expression of fibrosis markers, oxidative stress, and apoptosis compared with the already increased levels due to unilateral ureteral obstruction, whereas overexpression attenuated these effects. In conclusion, reduced LMX1B levels clearly represent a risk factor for renal fibrosis, whereas overexpression affords some level of protection. In general, LMX1B may be considered to be a negative regulator of the fibrosis index, transforming growth factor-βl, collagen type III, fibronectin, cleaved caspase-3, cell apoptosis, ROS, and malondialdehyde ( r = −0.756, −0.698, −0.921, −0.923, −0.843, −0.794, −0.883, and −0.825, all P < 0.01).

Association of prohibitin-1 and 2 with oxidative stress in rats with renal interstitial fibrosis

Prohibitins PHB1 and PHB2 are evolutionary conserved and pleiotropic proteins, which have been shown to be important factors in various cellular functions, including proliferation, tumour suppression, apoptosis, transcription, and mitochondrial protein folding. Recently, we demonstrated that down-regulation promoted renal interstitial fibrosis (RIF) in ureteral obstructed rats. Furthermore, the hypoxic conditions and oxidative stress have been implicated in obstruction-mediated renal disease. This study was performed to explore the association of PHBs with oxidative stress in a rat model of RIF. PHBs, the pro-fibrotic transforming growth factor-β1 (TGF-β1), and the extracellular matrix proteins collagen-IV (Col-IV) and fibronectin (FN) were evaluated, as were markers of oxidative stress [total reactive oxygen species (ROS), malondialdehyde (MDA)] and antioxidative capacity (superoxide dismutase, glutathione), and apoptosis. Our results showed a progressive increase in oxidative stress and concomitant decrease in antioxidants over a period of 4 weeks ureteral obstruction. Concomitantly, profibrotic components increased and PHB expression decreased. Overall, both PHBs were negatively correlated with the extent of observed fibrosis, TGF-β1, Col-IV, FN, ROS, MDA, and apoptosis.

The potential signal pathway between PAX2 and CD2AP in the renal interstitial fibrosis disease

Paired box gene 2 (PAX2) can regulate tissue development and cellular differentiation, and it is associated with renal diseases. CD2-associated protein (CD2AP) is an adaptor protein involving in a variety of physiological and disease processes. Renal interstitial fibrosis (RIF) is a hallmark of common progressive chronic diseases which lead to renal failure. This study was performed to investigate whether there was a potential signal pathway between PAX2 and CD2AP in RIF rats induced by unilateral ureteral obstruction (UUO). Eighty Wistar male rats were divided into two groups randomly: sham operation group (SHO) and model group subjected to UUO (GU), n = 40. The model was established by left ureteral ligation. Renal tissues were collected at 14 d and 28 d after surgery. RIF index, cell apoptosis index, protein expression of PAX2, CD2AP, transforming growth factor-βl (TGF-β1), collagen-IV (Col-IV), fibronectin (FN) in renal interstitium and renal tissue, and mRNA expression of PAX2, CD2AP, and TGF-β1 in renal tissue were detected. Compared with that in the SHO group, the PAX2 and CD2AP expressions (mRNA and protein) were significantly increased (p < 0.01). Protein expressions of TGF-β1, Col-IV, and FN, and RIF index or cell apoptosis index in the GU group were markedly elevated than those in the SHO group (all p < 0.01). PAX2 or CD2AP was positively correlated with TGF-β1, Col-IV, and FN, and RIF index or cell apoptosis index (all p < 0.05). Furthermore, PAX2 was positively correlated with CD2AP (p < 0.05). In conclusion, the expression of PAX2 or CD2AP was increased in RIF rats, and PAX2 was positively correlated with CD2AP. There might be a potential signaling pathway between PAX2 and CD2AP in RIF disease. Further research is needed to determine the association in RIF disease.

Association of retinoic acid receptors with extracellular matrix accumulation in rats with renal interstitial fibrosis disease

The nuclear retinoic acid receptors (RARs) function as ligand-dependent transcriptional regulators and include three subtypes (RARα, RARβ and RARγ), which control the expression of specific gene subsets subsequent to ligand binding and to strictly controlled phosphorylation processes. Extracellular matrix (ECM) accumulation is the most important characteristic of renal interstitial fibrosis (RIF). This study was performed to investigate whether RARs were associated with ECM accumulation in the progression of RIF in rats. Eighty Wistar male rats were divided into a sham operation group (SHO) and a model group subjected to unilateral ureteral obstruction (GU) at random; n = 40, respectively. The RIF disease in GU group was established by left ureteral ligation. The renal tissues were collected at two weeks and four weeks after surgery. Protein expressions of RARα, RARβ, RARγ, transforming growth factor-βl (TGF-β1), collagen-IV (Col-IV) and fibronectin (FN) were detected using immunohistochemical analysis, and mRNA expressions of RARα, RARβ, RARγ and TGF-β1 in renal tissue were detected by real time reverse transcription polymerase chain reaction. RIF index in renal interstitium was also calculated. When compared with those in SHO group, expressions of RARα and RARβ (protein and mRNA) were markedly reduced in the GU group (each p < 0.01). There was no marked difference for the expression of RARγ (protein and mRNA) between the SHO group and the GU group. The expressions of TGF-β1, Col-IV, FN and the RIF index in the GU group were markedly increased when compared with those in the SHO group (each p < 0.01). The protein expression of RARα/RARβ was negatively correlated with protein expression of TGF-β1, Col-IV or FN and the RIF index (all p < 0.01). In conclusion, the low expression of RARα/RARβ is associated with ECM accumulation in the progression of RIF in rats, suggesting that RARα/RARβ is a potentially therapeutic target for prevention of RIF.

Less expression of prohibitin is associated with increased paired box 2 (PAX2) in renal interstitial fibrosis rats

Prohibitin (PHB) and paired box 2 (PAX2) are associated with the development of renal interstitial fibrosis (RIF). This study was performed to investigate whether or not the PHB could regulate the PAX2 gene expression in unilateral ureteral obstruction (UUO) in rats. Eighty Wistar male rats were randomly divided into two groups: sham operation group (SHO) and model group subjected to unilateral ureteral obstruction (GU), n = 40, respectively. The model was established by left ureteral ligation. Renal tissues were collected at 14-day and 28-day after surgery. RIF index, protein expression of PHB, PAX2, transforming growth factor-βl (TGF-β1), α-smooth muscle actin (α-SMA), collagen-IV (Col-IV), fibronectin (FN) or cleaved Caspase-3, and cell apoptosis index in renal interstitium, and mRNA expressions of PHB, PAX2 and TGF-β1 in renal tissue were detected. When compared with those in SHO group, expression of PHB (mRNA and protein) was significantly reduced, and expressions of PAX2 and TGF-β1 (protein and mRNA) were markedly increased in the GU group (each p < 0.01). Protein expressions of α-SMA, Col-IV, FN and cleaved Caspase-3, and RIF index or cell apoptosis index in the GU group were markedly increased when compared with those in the SHO group (each p < 0.01). The protein expression of PHB was negatively correlated with protein expression of PAX2, TGF-β1, α-SMA, Col-IV, FN or cleaved Caspase-3, and RIF index or cell apoptosis index (all p < 0.01). In conclusion, less expression of PHB is associated with increased PAX2 gene expression and RIF index in UUO rats, suggesting that increasing the PHB expression is a potential therapeutic target for prevention of RIF.

HSP47 regulates ECM accumulation in renal proximal tubular cells induced by TGF-β1 through ERK1/2 and JNK MAPK pathways

Heat shock protein (HSP)47 is a collagen-specific molecular chaperone that is essential for the biosynthesis of collagen molecules. It is likely that increased levels of HSP47 contribute to the assembly of procollagen and thereby cause an excessive accumulation of collagens in disease processes associated with fibrosis. Although HSP47 promotes renal fibrosis, the underlying mechanism and associated signaling events have not been clearly delineated. We examined the role of HSP47 in renal fibrosis using a rat unilateral ureteral obstruction model and transforming growth factor (TGF)-β(1)-treated human proximal tubular epithelial (HK-2) cells. An upregulation of HSP47 in both in vivo and in vitro models was observed, which correlated with the increased synthesis of extracellular matrix (ECM) proteins and expression of tissue-type plasminogen activator inhibitor (PAI)-1. Blockade of HSP47 by short interfering RNA suppressed the expression of ECM proteins and PAI-1. In addition, TGF-β(1)-induced HSP47 expression in HK-2 cells was attenuated by ERK1/2 and JNK MAPK inhibitors. These data suggest that ERK1/2 and JNK signaling events are involved in modulating the expression of HSP47, the chaperoning effect of which on TGF-β(1) would ultimately contribute to renal fibrosis by enhancing the synthesis and deposition of ECM proteins.

Less expression of prohibitin is associated with increased caspase-3 expression and cell apoptosis in renal interstitial fibrosis rats

AIMS

Prohibitin (PHB), a ubiquitous protein, is involved in a variety of molecular functions. Renal interstitial fibrosis (RIF) is a hallmark of common progressive chronic diseases that lead to renal failure. This study was performed to investigate whether PHB was associated with caspase-3 expression/cell apoptosis in RIF rats.

METHODS

Twenty-four male Wistar rats were randomly divided into two groups: sham operation group (SHO) and model group subjected to unilateral ureteral obstruction (GU), n = 12, respectively. The model was established by left ureteral ligation. Renal tissues were collected at 14 days and 28 days after surgery. RIF index, cell apoptosis index, protein expression of PHB, transforming growth factor-βl (TGF-β1), collagen-IV (Col-IV), fibronectin (FN) or caspase-3 in renal interstitium, and mRNA expression of PHB in renal tissue were detected.

RESULTS

Compared with that in the SHO group, the PHB expression (mRNA and protein) was significantly reduced (P < 0.01). Protein expressions of TGF-β1, Col-IV, FN and caspase-3, and RIF index or cell apoptosis index in GU group were markedly elevated compared with those in SHO group (all P < 0.01). The protein expression of PHB had a negative correlation with the protein expression of TGF-β1, Col-IV, FN or caspase-3, and RIF index or cell apoptosis index (each P < 0.01).

CONCLUSIONS

Less expression of PHB is associated with increased caspase-3 expression/cell apoptosis in RIF rats. However, further research is needed to determine the effect of PHB on caspase-3 expression/cell apoptosis and to determine the potential of PHB as a therapeutic target.

Renal interstitial fibrosis: mechanisms and evaluation

PURPOSE OF REVIEW

Tubulointerstitial injury in the kidney is complex, involving a number of independent and overlapping cellular and molecular pathways, with renal interstitial fibrosis and tubular atrophy (IFTA) as the final common pathway. Furthermore, there are multiple ways to assess IFTA.

RECENT FINDINGS

Cells involved include tubular epithelial cells, fibroblasts, fibrocytes, myofibroblasts, monocyte/macrophages, and mast cells with complex and still incompletely characterized cell-molecular interactions. Molecular mediators involved are numerous and involve pathways such as transforming growth factor (TGF)-β, bone morphogenic protein (BMP), platelet-derived growth factor (PDGF), and hepatocyte growth factor (HGF). Recent genomic approaches have shed insight into some of these cellular and molecular pathways. Pathologic evaluation of IFTA is central in assessing the severity of chronic disease; however, there are a variety of methods used to assess IFTA. Most assessment of IFTA relies on pathologist assessment of special stains such as trichrome, Sirius Red, and collagen III immunohistochemistry. Visual pathologist assessment can be prone to intra and interobserver variability, but some methods employ computerized morphometery, without a clear consensus as to the best method.

SUMMARY

IFTA results from on orchestration of cell types and molecular pathways. Opinions vary on the optimal qualitative and quantitative assessment of IFTA.

All-trans retinoic acid treatment is associated with prohibitin expression in renal interstitial fibrosis rats

This study was performed to investigate the association of prohibitin with renal interstitial fibrosis (RIF) lesion and to explore the association of all-trans retinoic acid (ATRA) treatment with prohibitin expression in RIF rats. Rats were divided into three groups: the sham operation group (SHO), the model group subjected to unilateral ureteral obstruction (UUO), and the model group treated with ATRA (GA). Renal tissues were collected at 14 and 28 days after surgery, and the relevant indicators were detected. In comparison with the SHO group, the RIF index in the UUO group was markedly elevated (p < 0.01), and the RIF index in the GA group was alleviated compared with that in the UUO group (p < 0.01). Compared with the SHO group, the expression of prohibitin (protein or mRNA) in the UUO group was significantly reduced (each p < 0.01). Prohibitin expression in the GA group was markedly increased when compared with that in the UUO (p < 0.01). The expression of TGF-β1 (protein and mRNA), protein expressions of Col-IV, fibronectin, α-SMA and cleaved Caspase-3, ROS generation and cell apoptosis index in the UUO group were markedly higher than those in the SHO group (all p < 0.01), and their expressions in the GA group were markedly down-regulated compared to those in the UUO group (all p < 0.01, respectively). The protein expression of prohibitin was negatively correlated with the RIF index, protein expression of TGF-β1, Col-IV, fibronectin, α-SMA or cleaved Caspase-3, ROS generation and the cell apoptosis index (each p < 0.01). In conclusion, lower expression of prohibitin is associated with the RIF, and ATRA treatment is associated with increased prohibitin, which can prevent the progression of RIF.

Association of PAX2 with cell apoptosis in unilateral ureteral obstruction rats

Renal interstitial fibrosis (RIF) is the final common pathway for chronic kidney disease. Cell apoptosis is a critical detrimental event that leads to renal fibrosis. Paired box 2 (PAX2) plays a major role in the development of the kidney. This study was performed to investigate whether PAX2 was associated with cell apoptosis in the progression of RIF in unilateral ureteral obstruction (UUO) rats. Eighty Wistar male rats were divided into two groups randomly: sham operation group (SHO) and model group subjected to UUO (GU), n = 40, respectively. The model was established by left ureteral ligation. Renal tissues were collected 14 and 28 days after surgery. Protein expressions of PAX2, transforming growth factor-β1 (TGF-β1), α-smooth muscle actin (α-SMA), collagen-IV (Col-IV), fibronectin (FN), and caspase-3 were detected using immunohistochemical analysis; mRNA expression of PAX2 in renal tissue was detected by real-time reverse transcription polymerase chain reaction; and RIF index and cell apoptosis index in renal interstitium were also calculated. When compared with those in the SHO group, expressions of PAX2 (protein and mRNA) were markedly increased in the GU group (each p < 0.01). Protein expressions of TGF-β1, α-SMA, Col-IV, FN, and caspase-3 and RIF index and cell apoptosis index in the GU group were remarkably increased when compared with those in the SHO group (each p < 0.01). The protein expression of PAX2 was positively correlated with the protein expressions of TGF-β1, α-SMA, Col-IV, FN, and caspase-3 and with RIF index and cell apoptosis index (all p < 0.01). The apoptotic cell in our observation was mainly derived from renal tubular epithelial cells. In conclusion, the increased expression of PAX2 is associated with cell apoptosis in the progression of RIF in UUO rats, suggesting that PAX2 is a potentially therapeutic target for prevention of RIF. Tian-Biao Zhou and Yuan-Han Qin wish it to be known that, in their opinion, they should be regarded as joint first authors.

Role of extracellular matrix renal tubulo-interstitial nephritis antigen (TINag) in cell survival utilizing integrin (alpha)vbeta3/focal adhesion kinase (FAK)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B-serine/threonine kinase (AKT) signaling pathway

Tubulo-interstitial nephritis antigen (TINag) is an extracellular matrix protein expressed in tubular basement membranes. Combined mutations in TINag and nephrocystin-1 genes lead to nephronophthisis with reduced cell survival. Because certain extracellular matrix proteins are known to modulate cell survival, studies were initiated in Lewis rats lacking TINag to assess if they are more susceptible to cisplatin-induced injury. Cisplatin induced a higher degree of tubular cell damage and apoptosis in regions where TINag is expressed in a parental Wistar strain. This was accompanied by an accentuated increase in serum creatinine and Kim-1 RNA and renal expression of Bax, p53, and its nuclear accumulation, mtDNA fragmentation, and a decrease of Bcl-2. Cisplatin induced fulminant apoptosis of HK-2 cells with increased caspase3/7 activity, mtDNA fragmentation, and a reduced cell survival. These effects were partially reversed in cells maintained on TINag substratum. Far Western/solid phase assays established TINag binding with integrin αvβ3 comparable with vitronectin. Transfection of cells with αv-siRNA accentuated cisplatin-induced apoptosis, aberrant translocation of cytochrome c and Bax, and reduced cell survival. The αv-siRNA decreased expression of integrin-recruited focal adhesion kinase (FAK) and p-FAK, while increasing the expression of p53 and p-p53. Similarly, p-AKT was reduced although ILK was unaffected. Inhibition of PI3K had similar adverse cellular effects. These effects were ameliorated in cells on TINag substratum. In vivo, a higher degree of decrease in the expression of p-FAK and pAKT was observed in Lewis rats following cisplatin treatment. These in vivo and in vitro studies demonstrate an essential role of TINag in cellular survival to maintain proper tubular homeostasis utilizing integrin αvβ3 and downstream effectors.

Protective effects of IL-4 on Bacillus Calmette-Guerin and lipopolysaccharide induced immunological liver injury in mice

OBJECTIVE

Mice injected with Bacillus Calmette-Guérin (BCG) were challenged with lipopolysaccharide (LPS) to induce inflammatory liver injury. This study was performed to explore the protective effects of interleukin (IL)-4 against liver injury induced by BCG and LPS in mice.

MATERIALS AND METHODS

Mice injected with BCG (125 mg/kg) were challenged with LPS (10 μg/kg) to induce the model of inflammatory liver injury. Half an hour after injection of LPS, mice were subcutaneously administered rmIL-4 at 5 and 0.5 μg/kg, respectively. Liver injury was evaluated by serum transaminase assay and H & E staining. Liver cytokine concentrations were determined by enzyme-linked immunosorbent assay, and intrahepatic cytokine and iNOS mRNA levels by reverse transcriptase polymerase chain reaction. Intrahepatic apoptosis was evaluated by terminal deoxynucleotidyl transferase mediated nick end labeling. NF-κB p65 and ERK signal pathway was detected by Western-blotting. NF-κB signal pathway was also detected by electrophoretic mobility shift assay.

RESULTS

IL-4 reduced the serum ALT, AST and LDH, alleviated the inflammatory cells infiltration, down regulated the expression of TNF-α, IL-1β, IFN-γ, IL-6 and iNOS mRNA in liver, and alleviated hepatic glutathione depletion (GSH). In addition, IL-4 displayed inhibition of extracellular signal-regulated kinase phosphorylation and NF-κB activation.

CONCLUSION

IL-4 may protect mice against BCG/LPS-induced immune liver injury, besides ERK and NF-κB signal pathways were involved in the effects.

Transcriptional and post-translational modulation of myo-inositol oxygenase by high glucose and related pathobiological stresses

Renal-specific oxidoreductase/myo-inositol oxygenase (RSOR/MIOX) catabolizes myo-inositol and is implicated in the pathogenesis of diabetic nephropathy. How high glucose (HG) ambience up-regulates its expression and enzyme activity was investigated. MIOX up-regulation was associated with an increase in enzyme activity, which was reduced to basal levels with phosphatase treatment. Using phosphothreonine, protein kinase A (PKA), and PKC substrate antibodies, analyses of kidney lysates of diabetic animals and LLC-PK1/HK-2 cells subjected to HG ambience indicated MIOX to be a phosphoprotein. Kinase phosphorylated recombinant RSOR/MIOX proteins had increased activity confined to exons 2-5. Mutants with substituted phosphorylation sites had a minimal increase in activity. Treatment of cells with PKC, PKA, and PDK1 kinase activators increased activity, whereas inhibitors reduced it. Inhibitors also reduced the phosphorylation and activity of MIOX induced by HG. Besides HG, exposure of cells to oxidants H(2)O(2) and methylglyoxal up-regulated MIOX expression and its phosphorylation and activity, whereas antioxidants N-acetylcysteine, β-naphthoflavone, and tertiary butyl hydroquinone reduced MIOX expression. Treatment with HG or oxidants or overexpression of MIOX induced nuclear translocation of redox-sensitive transcription factor Nrf2, which binds to antioxidant response elements of various promoters. Promoter analyses revealed an increase in luciferase activity with HG and oxidants. Analyses of antioxidant response elements and carbohydrate response elements revealed an accentuation of DNA-protein interactions with oxidants and under HG ambience. ChIP-PCR and immunofluorescence studies revealed nuclear translocation of carbohydrate response element-binding protein. These findings suggest that phosphorylation of RSOR/MIOX enhances its activity, which is augmented by HG via transcriptional/translational events that are also modulated by diabetes-related pathobiological stresses.

Renal fibrosis: novel insights into mechanisms and therapeutic targets

Renal fibrosis is the common end point of virtually all progressive kidney diseases. Renal fibrosis should not be viewed as a simple and uniform 'scar', but rather as a dynamic system that involves extracellular matrix components and many, if not all, renal and infiltrating cell types. The involved cells exhibit enormous plasticity or phenotypic variability-a fact that we are only beginning to appreciate. Only a detailed understanding of the underlying mechanisms of renal fibrosis can facilitate the development of effective treatments. In this Review, we discuss the most recent advances in renal, or more specifically, tubulointerstitial fibrosis. Novel mechanisms as well as potential treatment targets based on different cell types are described. Problems that continue to plague the field are also discussed, including specific therapeutic targeting of the kidney, the development of improved diagnostic methods to assess renal fibrosis and the shortcomings of available animal models.

Oxidative stress in obstructive nephropathy

Unilateral ureteric obstruction (UUO) is one of the most commonly applied rodent models to study the pathophysiology of renal fibrosis. This model reflects important aspects of inflammation and fibrosis that are prominent in human kidney diseases. In this review, we present an overview of the factors contributing to the pathophysiology of UUO, highlighting the role of oxidative stress.

Pathobiology of renal-specific oxidoreductase/myo-inositol oxygenase in diabetic nephropathy: its implications in tubulointerstitial fibrosis

Renal-specific oxido-reductase/myoinositol oxygenase (RSOR/MIOX) is expressed in renal tubules. It catabolizes myo-inositol and its expression is increased in diabetic mice and in LLC-PK(1) cells under high-glucose ambience. Aldose reductase (AR) is another aldo-keto reductase that is expressed in renal tubules. It regulates the polyol pathway and plays an important role in glucose metabolism, osmolyte regulation, and ECM pathobiology via the generation of advanced glycation end products, reactive oxygen species, and activation of transforming growth factor (TGF)-beta. In view of the similarities between AR and RSOR/MIOX, the pathobiology of RSOR/MIOX and some of the cellular pathways affected by its overexpression were investigated. An increased expression of fibronectin was noted by transfection of LLC-PK(1) cells with pcDNA3.1-RSOR/MIOX. Similar changes were observed in LLC-PK(1) cells under high-glucose ambience, and they were notably lessened by RSOR/MIOX-small interfering (si) RNA treatment. The changes in tubulointerstitial fibronectin expression were also observed in the kidneys of db/db mice having high levels of RSOR. The pcDNA3.1-RSOR/MIOX transfectants had an increased NADH/NAD(+) ratio, PKC and TGF-beta activity, Raf1:Ras association, and p-ERK phosphorylation. These changes were significantly reduced by the inhibitors of PKC, aldose reductase, Ras farnesylation, and MEK1. Similar increases in various the above-noted parameters were observed under high-glucose ambience. Such changes were partially reversed with RSOR-siRNA treatment. Expression of E-cadherin and vimentin paralleled in cells overexpressing RSOR/MIOX or subjected to high-glucose ambience. These studies suggest that RSOR/MIOX modulates various downstream pathways affected by high-glucose ambience, and conceivably it plays a role in the pathobiology of tubulointerstitium in diabetic nephropathy.