NFkappaB promotes inflammation, coagulation, and fibrosis in the aging glomerulus

Targeting endothelin signaling in podocyte injury and diabetic nephropathy-diabetic kidney disease

Despite advances in diabetes management, there is an urgent need for novel therapeutic strategies since the current treatments remain insufficient in halting the progression of diabetic nephropathy-diabetic kidney disease (DN-DKD). This review is mainly addressed on the pivotal role of endothelin-1 in the pathophysiology of DN, with a specific focus on its effects on podocytes and the glomerular filtration barrier. Endothelin-1 promotes mesangial cell proliferation, sclerosis, and direct podocyte injury via the activation of endothelin type A and B receptors, that drive the progression of glomerulosclerosis in DN-DKD. Endothelin receptor antagonists, including drugs like atrasentan and sparsentan, have demonstrated nephroprotective effects in experimental models by reducing proteinuria and podocyte injury. The therapeutic potential to slow the progression of DN to end-stage kidney disease (ESKD) of these endothelin receptor antagonists in clinical practice is currently under evaluation. However, fluid retention and increased risk of heart failure associated with endothelin receptor antagonists need careful consideration. This review aims to provide an in-depth analysis of the pathophysiological role of endothelin and the emerging therapeutic implications of targeting this pathway in DN-DKD and discusses efficacy, safety, and the possibility of combining the new generation of endothelin receptor antagonists with the standard treatment of CKD and DN-DKD.

Endothelial Dysfunction Biomarkers and CKD Incidence in the REGARDS Cohort

Introduction

Chronic kidney disease (CKD) is only partly caused by traditional risk factors. Endothelial dysfunction is common in CKD and may contribute to CKD incidence. We studied the association of circulating biomarkers reflecting endothelial dysfunction with incident CKD.

Methods

The Reasons for Geographical and Racial Differences in Stroke (REGARDS) study is a prospective cohort of 30,239 Black or White adults aged ≥45 years. Baseline levels of intercellular cellular adhesion molecule 1 (ICAM-1), vascular cellular adhesion molecule 1 (VCAM-1), factor VIII (FVIII), and E-selectin were measured in 3300 participants without baseline CKD or albuminuria who attended a second visit 9.4 years later. Kidney outcomes were incident CKD (estimated glomerular filtration rate [eGFR] <60 ml/min per 1.73 m2 and ≥40% decline or onset of new end-stage kidney disease), incident ≥30% eGFR decline, and incident albuminuria (albumin-to-creatinine ratio [ACR] ≥30 mg/g). Sequentially adjusted logistic regression models assessed the association of biomarkers with kidney outcomes.

Results

Median age of participants was 62 years, 49% were women, and 46% identified as Black. Of the participants, 228 (6.9%) developed CKD, 613 (18.9%) experienced ≥30% decline in eGFR, and 356 (11.4%) developed albuminuria. The adjusted odds ratios (ORs) for incident CKD per 1 SD increment biomarker was 1.12 for ICAM-1 (95% confidence interval [CI]: 1.02-1.22), 1.10 for VCAM-1 (95% CI: 1.01-1.20), 1.15 for FVIII (95% CI: 1.06-1.24), and 1.10 for E-selectin (95% CI: 1.01-1.20). Results were similar for incident ≥30% eGFR decline but not albuminuria, where only higher FVIII was positively associated.

Conclusion

Higher concentration of ICAM-1, VCAM-1, FVIII, and E-selectin were associated with incident CKD and ≥30% eGFR decline in a large cohort study. Higher FVIII was also associated with incident albuminuria.

Epigenetically regulated inflammation in vascular senescence and renal progression of chronic kidney disease

Chronic kidney disease (CKD) and its complications, including vascular senescence and progressive renal fibrosis, are associated with inflammation. Vascular senescence, in particular, has emerged as an instrumental mediator of vascular inflammation that potentially worsens renal function. Epigenetically regulated inflammation involving histone modification, DNA methylation, actions of microRNAs and other non-coding RNAs, and their reciprocal reactions during vascular senescence and inflammaging are underappreciated. Their synergistic effects can contribute to CKD progression. Vascular senotherapeutics or pharmacological anti-senescent therapies based on epigenetic machineries can therefore be plausible options for ameliorating vascular aging and even halting the worsening of renal fibrosis. These include histone deacetylase modulators, histone methyltransferase modulators, other histone modification effectors, DNA methyltransferase inhibitors, telomerase reverse transcriptase enhancers, microRNA mimic delivery, and small molecules with microRNA-regulating potentials. Some of these molecules have already been tested and have shown anecdotal evidence for treating uremic vasculopathy and renal fibrosis, supporting the feasibility of this approach.

Precision nephrology identified tumor necrosis factor activation variability in minimal change disease and focal segmental glomerulosclerosis

The diagnosis of nephrotic syndrome relies on clinical presentation and descriptive patterns of injury on kidney biopsies, but not specific to underlying pathobiology. Consequently, there are variable rates of progression and response to therapy within diagnoses. Here, an unbiased transcriptomic-driven approach was used to identify molecular pathways which are shared by subgroups of patients with either minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS). Kidney tissue transcriptomic profile-based clustering identified three patient subgroups with shared molecular signatures across independent, North American, European, and African cohorts. One subgroup had significantly greater disease progression (Hazard Ratio 5.2) which persisted after adjusting for diagnosis and clinical measures (Hazard Ratio 3.8). Inclusion in this subgroup was retained even when clustering was limited to those with less than 25% interstitial fibrosis. The molecular profile of this subgroup was largely consistent with tumor necrosis factor (TNF) pathway activation. Two TNF pathway urine markers were identified, tissue inhibitor of metalloproteinases-1 (TIMP-1) and monocyte chemoattractant protein-1 (MCP-1), that could be used to predict an individual's TNF pathway activation score. Kidney organoids and single-nucleus RNA-sequencing of participant kidney biopsies, validated TNF-dependent increases in pathway activation score, transcript and protein levels of TIMP-1 and MCP-1, in resident kidney cells. Thus, molecular profiling identified a subgroup of patients with either MCD or FSGS who shared kidney TNF pathway activation and poor outcomes. A clinical trial testing targeted therapies in patients selected using urinary markers of TNF pathway activation is ongoing.

Activation of STAT3 signaling pathway in the kidney of COVID-19 patients

BACKGROUND

Acute kidney injury is common in patients with COVID-19, however mechanisms of kidney injury remain unclear. Since cytokine storm is likely a cause of AKI and glomerular disease, we investigated the two major transcription factors, STAT3 and NF-kB, which are known to be activated by cytokines.

METHODS

This is an observational study of the postmortem kidneys of 50 patients who died with COVID-19 in the Mount Sinai Hospital during the first pandemic surge. All samples were reviewed under light microscopy, electron microscopy, and immunofluorescence by trained renal pathologists. In situ hybridization evaluation for SARS-CoV-2 and immunostaining of transcription factors STAT3 and NF-kB were performed.

RESULTS

Consistent with previous findings, acute tubular injury was the major pathological finding, together with global or focal glomerulosclerosis. We were not able to detect SARS-CoV-2 in kidney cells. ACE2 expression was reduced in the tubular cells of patients who died with COVID-19 and did not co-localize with TMPRSS2. SARS-CoV-2 was identified occasionally in the mononuclear cells in the peritubular capillary and interstitium. STAT3 phosphorylation at Tyr705 was increased in 2 cases in the glomeruli and in 3 cases in the tubulointerstitial compartments. Interestingly, STAT3 phosphorylation at Ser727 increased in 9 cases but only in the tubulointerstitial compartment. A significant increase in NF-kB phosphorylation at Ser276 was also found in the tubulointerstitium of the two patients with increased p-STAT3 (Tyr705).

CONCLUSIONS

Our findings suggest that, instead of tyrosine phosphorylation, serine phosphorylation of STAT3 is commonly activated in the kidney of patients with COVID-19.

Podocyte Aging: Why and How Getting Old Matters

The effects of healthy aging on the kidney, and how these effects intersect with superimposed diseases, are highly relevant in the context of the population's increasing longevity. Age-associated changes to podocytes, which are terminally differentiated glomerular epithelial cells, adversely affect kidney health. This review discusses the molecular and cellular mechanisms underlying podocyte aging, how these mechanisms might be augmented by disease in the aged kidney, and approaches to mitigate progressive damage to podocytes. Furthermore, we address how biologic pathways such as those associated with cellular growth confound aging in humans and rodents.

The Aging Kidney-As Influenced by Heavy Metal Exposure and Selenium Supplementation

The aging process in the kidneys has been well studied. It is known that the glomerular filtration rate (GFR) declines with age in subjects older than 50–60 years. However, there is still insufficient knowledge regarding the response of the aged kidney to environmental toxicants such as mercury, cadmium, and lead. Here, we present a review on the functional decline and proposed mechanisms in the aging kidney as influenced by metal pollutants. Due to the prevalence of these toxicants in the environment, human exposure is nearly unavoidable. Further, it is well known that acute and chronic exposures to toxic metals may be detrimental to kidneys of normal adults, thus it may be hypothesized that exposure of individuals with reduced GFR will result in additional reductions in renal function. Individuals with compromised renal function, either from aging or from a combination of aging and disease, may be particularly susceptible to environmental toxicants. The available data appear to show an association between exposure to mercury, cadmium and/or lead and an increase in incidence and severity of renal disease in elderly individuals. Furthermore, some physiological thiols, as well as adequate selenium status, appear to exert a protective action. Further studies providing improved insight into the mechanisms by which nephrotoxic metals are handled by aging kidneys, as well as possibilities of therapeutic protection, are of utmost importance.

Retinoic acid receptor responder1 promotes development of glomerular diseases via the Nuclear Factor-κB signaling pathway

Inflammatory pathways are activated in most glomerular diseases but molecular mechanisms driving them in kidney tissue are poorly known. We identified retinoic acid receptor responder 1 (Rarres1) as a highly podocyte-enriched protein in healthy kidneys. Studies in podocyte-specific knockout animals indicated that Rarres1 was not needed for the normal development or maintenance of the glomerulus filtration barrier and did not modulate the outcome of kidney disease in a model of glomerulonephritis. Interestingly, we detected an induction of Rarres1 expression in glomerular and peritubular capillary endothelial cells in IgA and diabetic kidney disease, as well as in ANCA-associated vasculitis. Analysis of publicly available RNA data sets showed that the induction of Rarres1 expression was a common molecular mechanism in chronic kidney diseases. A conditional knock-in mouse line, overexpressing Rarres1 specifically in endothelial cells, did not show any obvious kidney phenotype. However, the overexpression promoted the progression of kidney damage in a model of glomerulonephritis. In line with this, conditional knock-out mice, lacking Rarres1 in endothelial cells, were partially protected in the disease model. Mechanistically, Rarres1 promoted inflammation and fibrosis via transcription factor Nuclear Factor-κB signaling pathway by activating receptor tyrosine kinase Axl. Thus, induction of Rarres1 expression in endothelial cells is a prevalent molecular mechanism in human glomerulopathies and this seems to have a pathogenic role in driving inflammation and fibrosis via the Nuclear Factor-κB signaling pathway.

Generation of a novel decay accelerating factor (DAF) knock-out rat model using clustered regularly-interspaced short palindromic repeats, (CRISPR)/associated protein 9 (Cas9), genome editing

Decay accelerating factor (DAF), a key complement activation control protein, is a 70 kDa membrane bound glycoprotein which controls extent of formation of the C3 and C5 convertases by accelerating their decay. Using clustered regularly-interspaced short palindromic repeats, (CRISPR)/associated protein 9 (Cas9) genome editing we generated a novel DAF deficient (Daf^-/-) rat model. The present study describes the renal and extrarenal phenotype of this model and assesses renal response to complement-dependent injury induced by administration of a complement-fixing antibody (anti-Fx1A) against the glomerular epithelial cell (podocyte). Rats generated were healthy, viable and able to reproduce normally. Complete absence of DAF was documented in renal as well as extra-renal tissues at both protein and mRNA level compared to Daf^+/+ rats. Renal histology in Daf^-/- rats showed no differences regarding glomerular or tubulointerstitial pathology compared to Daf^+/+ rats. Moreover, there was no difference in urine protein excretion (ratio of urine albumin to creatinine) or in serum creatinine and urea levels. In Daf^-/- rats, proteinuria was significantly increased following binding of anti-Fx1A antibody to podocytes while increased C3b deposition was observed. The DAF knock-out rat model developed validates the role of this complement cascade regulator in immune-mediated podocyte injury. Given the increasing role of dysregulated complement activation in various forms of kidney disease and the fact that the rat is the preferred animal for renal pathophysiology studies, the rat DAF deficient model may serve as a useful tool to study the role of this complement activation regulator in complement-dependent forms of kidney injury.

Soluble RARRES1 induces podocyte apoptosis to promote glomerular disease progression

Using the Nephrotic Syndrome Study Network Consortium data set and other publicly available transcriptomic data sets, we identified retinoic acid receptor responder protein 1 (RARRES1) as a gene whose expression positively correlated with renal function decline in human glomerular disease. The glomerular expression of RARRES1, which is largely restricted to podocytes, increased in focal segmental glomerulosclerosis (FSGS) and diabetic kidney disease (DKD). TNF-α was a potent inducer of RARRES1 expression in cultured podocytes, and transcriptomic analysis showed the enrichment of cell death pathway genes with RARRES1 overexpression. The overexpression of RARRES1 indeed induced podocyte apoptosis in vitro. Notably, this effect was dependent on its cleavage in the extracellular domain, as the mutation of its cleavage site abolished the apoptotic effect. Mechanistically, the soluble RARRES1 was endocytosed and interacted with and inhibited RIO kinase 1 (RIOK1), resulting in p53 activation and podocyte apoptosis. In mice, podocyte-specific overexpression of RARRES1 resulted in marked glomerular injury and albuminuria, while the overexpression of RARRES1 cleavage mutant had no effect. Conversely, podocyte-specific knockdown of Rarres1 in mice ameliorated glomerular injury in the setting of adriamycin-induced nephropathy. Our study demonstrates an important role and the mechanism of RARRES1 in podocyte injury in glomerular disease.

Downregulated PEG3 ameliorates cardiac fibrosis and myocardial injury in mice with ischemia/reperfusion through the NF-κB signaling pathway

Expression of paternally-expressed gene 3 (PEG3) has been identified in new cardiac adult stem cell population, which is involved in post-myocardial infarction remodeling. The cardiac fibroblasts function in the repair and remodeling events after myocardial ischemia, while the role of PEG3 in these events has not been investigated yet. In this study, artificial knockdown of PEG3 through p-LV-GFP-sh-PEG3 injection was performed in a ischemia/reperfusion (I/R) mouse model to explore the role of PEG3 in cardiac fibrosis, myocardial injury and cardiomyocyte apoptosis. Besides, the involvement of nuclear factor kappa B (NF-κB) pathway was illuminated by transduction of inhibitor pyrrolidine dithiocarbamate (PDTC). Both shRNA-mediated silencing of PEG3 and inhibition of the NF-κB signaling pathway were shown to significantly reduce myocardial injury, infarction size, alleviated myocardium remodeling and cardiac fibrosis, along with repressed cardiomyocyte apoptosis. Additionally, we also found that the NF-κB signaling pathway activation was blocked by PEG3 silencing, which could further enhance the protective effects of PEG3 inhibition against I/R induced injury. This study highlights the importance of PEG3 silencing in preventing cardiac fibrosis and myocardial injury after I/R by inactivating the NF-κB signaling pathway.

Anti-aging Effects of Calorie Restriction (CR) and CR Mimetics based on the Senoinflammation Concept

Chronic inflammation, a pervasive feature of the aging process, is defined by a continuous, multifarious, low-grade inflammatory response. It is a sustained and systemic phenomenon that aggravates aging and can lead to age-related chronic diseases. In recent years, our understanding of age-related chronic inflammation has advanced through a large number of investigations on aging and calorie restriction (CR). A broader view of age-related inflammation is the concept of senoinflammation, which has an outlook beyond the traditional view, as proposed in our previous work. In this review, we discuss the effects of CR on multiple phases of proinflammatory networks and inflammatory signaling pathways to elucidate the basic mechanism underlying aging. Based on studies on senoinflammation and CR, we recognized that senescence-associated secretory phenotype (SASP), which mainly comprises cytokines and chemokines, was significantly increased during aging, whereas it was suppressed during CR. Further, we recognized that cellular metabolic pathways were also dysregulated in aging; however, CR mimetics reversed these effects. These results further support and enhance our understanding of the novel concept of senoinflammation, which is related to the metabolic changes that occur in the aging process. Furthermore, a thorough elucidation of the effect of CR on senoinflammation will reveal key insights and allow possible interventions in aging mechanisms, thus contributing to the development of new therapies focused on improving health and longevity.

Identification of proteins potentially associated with renal aging in rats

We established a young (Y)-old (O) rat kidney transplantation model. With this model, we detected no age-related differences in renal structure between Y→Y and Y→O kidneys or O→O and O→Y kidneys. However, we did detect differences in levels of the senescence markers β-gal and p16 as well as the inflammatory cytokines TNF-α and IL-1β. Using proteomics analysis we detected 66 proteins associated with suppression of aging and 73 proteins associated with enhancement of aging. After construction of a protein-protein interaction network, a total of 73 nodes and 99 edges were analyzed using MCODE, and three significant modules were selected. GO and KEGG analyses showed that these proteins were mainly located in mitochondria and were largely related to oxidative stress. Among them, SOD1 expression was lower in Y→O than Y→Y kidneys and higher in O→Y than O→O kidneys. Acetylated (Ac)-NF-κB showed the opposite expression profile. In addition, SOD1 expression was higher in primary tubular epithelial cells from young rats than old rats, and SOD1 knockdown led to increased Ac-NF-κB expression. These findings suggest the local renal environment, particularly oxidative stress/mitochondrial function, affects renal aging.

Glomerular function in relation to circulating adhesion molecules and inflammation markers in a general population

Background

Inflammation is a hallmark of chronic kidney disease (CKD) and stimulates glomerular expression of vascular adhesion molecules (VCAMs). We investigated in a general population whether estimated glomerular filtration rate (eGFR) is associated with circulating adhesion molecules, inflammation markers or both.

Methods

We measured serum levels of five adhesion molecules [VCAM-1, intracellular adhesion molecule-1 (ICAM-1), P-selectin, E-selectin and monocyte chemoattractant protein-1 (MCP-1)] and seven inflammation markers [C-reactive protein (CRP), neutrophil gelatinase-associated lipocalin (NGAL), tumour necrosis factor receptor 1 (TNF-R1), TNF-α, interleukin 6 (IL-6), IL-8 and vascular endothelial growth factor] in 1338 randomly recruited people (50.8% women, mean age 51.7 years, eGFR 79.9 mL/min/1.73 m²).

Results

In multivariable-adjusted analyses, eGFR decreased (P ≤ 0.004) with higher VCAM-1 (association size expressed in mL/min/1.73 m² for a doubling of the marker, −2.99), MCP-1 (−1.19), NGAL (−1.19), TNF receptor 1 (−2.78), TNF-α (−2.28) and IL-6 (−0.94). The odds ratios of having eGFR <60 versus ≥60 mL/min/1.73 m² (n = 138 versus 1200) were significant (P ≤ 0.001) for VCAM-1 (1.77), MCP-1 (1.32), NGAL (1.26), TNF-R1 (1.49), TNF-α (1.45) and IL-6 (1.20). Compared with 24-h albuminuria, VCAM-1 increased (P <0.0001) the area under the curve from 0.57 to 0.65, MCP-1 to 0.67 and TNF-R1 to 0.79, but TNF-R1 outperformed both adhesion molecules (P < 0.0001).

Conclusions

In a general population, eGFR is inversely associated with circulating adhesion molecules VCAM-1 and MCP-1 and several inflammation markers, but inflammation markers, in particular TNF-R1 and TNF-α, identify patients with eGFR <60 mL/min/1.73 m² more accurately.

A Young Blood Environment Decreases Aging of Senile Mice Kidneys

Whether changes in internal body environment affect kidney aging remains unclear. Specifically, it is unknown whether transplanted kidneys from older donors recover from tissue damage after placement in younger recipients. In this study, a parabiosis animal model was established to investigate the effects of a young internal body environment on aged kidneys. The animals were divided into six groups: young (Ycon) and old control (Ocon) groups, isochronic youth-youth group (Y-IP), elderly-elderly group (O-IP), and heterochronic youth (Y-HP) and elderly (O-HP) groups. After parabiosis, tubule and interstitial tissue scores in the O-HP group were significantly lower than in the Ocon and O-IP groups. The expression of aging-related protein p16 and SA-β-gal in the O-HP group was significantly reduced compared with the Ocon and O-IP groups. Autophagy factors Atg5 and LC3BII were significantly upregulated, whereas the expression of the autophagic degradation marker (P62) was significantly downregulated in the O-HP group compared with the Ocon and O-IP groups. With the same comparison, the positive cells of TUNEL staining and the expression of IL-6 and IL-1β were significantly reduced, whereas the total/cleaved caspase-3 and total/pNF-κB were significantly increased in the O-HP group. The results demonstrated that a young blood environment significantly reduces kidney aging. These findings provide new evidence supporting an increase in the upper age limit for human kidney transplantation donors.

Tyro3 is a podocyte protective factor in glomerular disease

Our previous work demonstrated a protective role of protein S in early diabetic kidney disease (DKD). Protein S exerts antiinflammatory and antiapoptotic effects through the activation of TYRO3, AXL, and MER (TAM) receptors. Among the 3 TAM receptors, we showed that the biological effects of protein S were mediated largely by TYRO3 in diabetic kidneys. Our data now show that TYRO3 mRNA expression is highly enriched in human glomeruli and that TYRO3 protein is expressed in podocytes. Interestingly, glomerular TYRO3 mRNA expression increased in mild DKD but was suppressed in progressive DKD, as well as in focal segmental glomerulosclerosis (FSGS). Functionally, morpholino-mediated knockdown of tyro3 altered glomerular filtration barrier development in zebrafish larvae, and genetic ablation of Tyro3 in murine models of DKD and Adriamycin-induced nephropathy (ADRN) worsened albuminuria and glomerular injury. Conversely, the induction of TYRO3 overexpression specifically in podocytes significantly attenuated albuminuria and kidney injury in mice with DKD, ADRN, and HIV-associated nephropathy (HIVAN). Mechanistically, TYRO3 expression was suppressed by activation of TNF-α/NF-κB pathway, which may contribute to decreased TYRO3 expression in progressive DKD and FSGS, and TYRO3 signaling conferred antiapoptotic effects through the activation of AKT in podocytes. In conclusion, TYRO3 plays a critical role in maintaining normal podocyte function and may be a potential new drug target to treat glomerular diseases.

Oridonin protects against the inflammatory response in diabetic nephropathy by inhibiting the TLR4/p38-MAPK and TLR4/NF-κB signaling pathways

Inflammation plays a pivotal role in the development and progression of diabetic nephropathy (DN). Oridonin (Ori), a component isolated from Rabdosia rubescens, possesses remarkable anti-inflammatory, immunoregulatory and antitumor properties. However, the renoprotective effects of Ori and the underlying molecular mechanisms have not been explored in DN. In this study, we aimed to investigate the protective effects and potential mechanisms responsible for the anti-inflammatory effects of Ori in diabetes-induced renal injury in vivo and in vitro. Our results showed that Ori significantly attenuated diabetes-induced renal injury and markedly decreased urinary protein excretion levels, serum creatinine concentrations and blood urea nitrogen concentrations in rats. Ori also significantly alleviated infiltration of inflammatory cells (cluster of differentiation (CD)68) in kidney tissues and reduced the levels of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-1β and monocyte chemotactic protein 1 (MCP-1), both in vivo and in vitro. TLR4 is a principal mediator of innate immune and inflammatory responses and participates in the development of DN. Our molecular studies indicated that Ori administration significantly down-regulated TLR4 overexpression in DN. Additional studies were conducted to investigate the effect of Ori on the p38-mitogen-activated protein kinase (p38-MAPK) and nuclear factor (NF)-κB pathways. The results showed that Ori inhibited IκBα, p65, and p38 phosphorylation, as well as NF-κB DNA-binding activity. In conclusion, these results demonstrated that Ori exerts protective effects in diabetes-induced renal injury in vivo and in vitro. These effects may be ascribed to its anti-inflammatory and modulatory effects on the TLR4/p38-MAPK and TLR4/NF-κB signaling pathways.

A molecular morphometric approach to diabetic kidney disease can link structure to function and outcome

Diabetic kidney disease is the leading cause of kidney failure. However, studies of molecular mechanisms of early kidney damage are lacking. Here we examined for possible linkage between transcriptional regulation and quantitative structural damage in early diabetic kidney disease in Pima Indians with type 2 diabetes. Tissue obtained from protocol kidney biopsies underwent genome-wide compartment-specific gene expression profiling and quantitative morphometric analysis. The ultrastructural lesion most strongly associated with transcriptional regulation was cortical interstitial fractional volume (VvInt), an index of tubule-interstitial damage. Transcriptional co-expression network analysis identified 1843 transcripts that correlated significantly with VvInt. These transcripts were enriched for pathways associated with mitochondrial dysfunction, inflammation, migratory mechanisms, and tubular metabolic functions. Pathway network analysis identified IL-1β as a key upstream regulator of the inflammatory response and five transcription factors cooperating with p53 to regulate metabolic functions. VvInt-associated transcripts showed significant correlation with the urine albumin to creatinine ratio and measured glomerular filtration rate 10 years after biopsy, establishing a link between the early molecular events and long-term disease progression. Thus, molecular mechanisms active early in diabetic kidney disease were revealed by correlating intrarenal transcripts with quantitative morphometry and long-term outcomes. This provides a starting point for identification of urgently needed therapeutic targets and non-invasive biomarkers of early diabetic kidney disease.

Cellular senescence, senescence-associated secretory phenotype, and chronic kidney disease

Chronic kidney disease (CKD) is increasingly being accepted as a type of renal ageing. The kidney undergoes age-related alterations in both structure and function. To date, a comprehensive analysis of cellular senescence and senescence-associated secretory phenotype (SASP) in CKD is lacking. Hence, this review mainly discusses the relationship between the two phenomena to show the striking similarities between SASP and CKD-associated secretory phenotype (CASP). It has been reported that replicative senescence, stress-induced premature ageing, and epigenetic abnormalities participate in the occurrence and development of CKD. Genomic damage and external environmental stimuli cause increased levels of oxidative stress and a chronic inflammatory state as a result of irreversible cell cycle arrest and low doses of SASP. Similar to SASP, CASP factors activate tissue repair by multiple mechanisms. Once tissue repair fails, the accumulated SASP or CASP species aggravate DNA damage response (DDR) and cause the senescent cells to secrete more SASP factors, accelerating the process of cellular ageing and eventually leading to various ageing-related changes. It is concluded that cellular senescence and SASP participate in the pathological process of CKD, and correspondingly CKD accelerated the progression of cell senescence and the secretion of SASP. These results will facilitate the integration of these mechanisms into the care and management of CKD and other age-related diseases.

Disease drivers of aging

It has long been known that aging, at both the cellular and organismal levels, contributes to the development and progression of the pathology of many chronic diseases. However, much less research has examined the inverse relationship-the contribution of chronic diseases and their treatments to the progression of aging-related phenotypes. Here, we discuss the impact of three chronic diseases (cancer, HIV/AIDS, and diabetes) and their treatments on aging, putative mechanisms by which these effects are mediated, and the open questions and future research directions required to understand the relationships between these diseases and aging.

FSGS as an Adaptive Response to Growth-Induced Podocyte Stress

Glomerular sclerotic lesions develop when the glomerular filtration surface area exceeds the availability of podocyte foot process coverage, but the mechanisms involved are incompletely characterized. We evaluated potential mechanisms using a transgenic (podocin promoter-AA-4E-BP1) rat in which podocyte capacity for hypertrophy in response to growth factor/nutrient signaling is impaired. FSGS lesions resembling human FSGS developed spontaneously by 7 months of age, and could be induced earlier by accelerating kidney hypertrophy by nephrectomy. Early segmental glomerular lesions occurred in the absence of a detectable reduction in average podocyte number per glomerulus and resulted from the loss of podocytes in individual glomerular capillary loops. Parietal epithelial cell division, accumulation on Bowman's capsule, and tuft invasion occurred at these sites. Three different interventions that prevented kidney growth and glomerular enlargement (calorie intake reduction, inhibition of mammalian target of rapamycin complex, and inhibition of angiotensin-converting enzyme) protected against FSGS lesion development, even when initiated late in the process. Ki67 nuclear staining and unbiased transcriptomic analysis identified increased glomerular (but not podocyte) cell cycling as necessary for FSGS lesion development. The rat FSGS-associated transcriptomic signature correlated with human glomerular transcriptomes associated with disease progression, compatible with similar processes occurring in man. We conclude that FSGS lesion development resulted from glomerular growth that exceeded the capacity of podocytes to adapt and adequately cover some parts of the filtration surface. Modest modulation of the growth side of this equation significantly ameliorated FSGS progression, suggesting that glomerular growth is an underappreciated therapeutic target for preservation of renal function.

The aging kidney and the nephrotoxic effects of mercury

Owing to advances in modern medicine, life expectancies are lengthening and leading to an increase in the population of older individuals. The aging process leads to significant alterations in many organ systems, with the kidney being particularly susceptible to age-related changes. Within the kidney, aging leads to ultrastructural changes such as glomerular and tubular hypertrophy, glomerulosclerosis, and tubulointerstitial fibrosis, which may compromise renal plasma flow (RPF) and glomerular filtration rate (GFR). These alterations may reduce the functional reserve of the kidneys, making them more susceptible to pathological events when challenged or stressed, such as following exposure to nephrotoxicants. An important and prevalent environmental toxicant that induces nephrotoxic effects is mercury (Hg). Since exposure of normal kidneys to mercuric ions might induce glomerular and tubular injury, aged kidneys, which may not be functioning at full capacity, may be more sensitive to the effects of Hg than normal kidneys. Age-related renal changes and the effects of Hg in the kidney have been characterized separately. However, little is known regarding the influence of nephrotoxicants, such as Hg, on aged kidneys. The purpose of this review was to summarize known findings related to exposure of aged and diseased kidneys to the environmentally relevant nephrotoxicant Hg.

Inflammation and elevated levels of fibroblast growth factor 23 are independent risk factors for death in chronic kidney disease

Inflammation is a consequence of chronic kidney disease (CKD) and is associated with adverse outcomes in many clinical settings. Inflammation stimulates production of fibroblast growth factor 23 (FGF23), high levels of which are independently associated with mortality in CKD. Few large-scale prospective studies have examined inflammation and mortality in patients with CKD, and none tested the interrelationships among inflammation, FGF23, and risk of death. Therefore, we conducted a prospective investigation of 3875 participants in the Chronic Renal Insufficiency Cohort (CRIC) study with CKD stages 2 to 4 to test the associations of baseline plasma interleukin-6, high-sensitivity C-reactive protein, and FGF23 levels with all-cause mortality, censoring at the onset of end-stage renal disease. During a median follow-up of 6.9 years, 550 participants died (20.5/1000 person-years) prior to end-stage renal disease. In separate multivariable-adjusted analyses, higher levels of interleukin-6 (hazard ratio per one standard deviation increase of natural log-transformed levels) 1.35 (95% confidence interval, 1.25-1.46), C-reactive protein 1.28 (1.16-1.40), and FGF23 1.45 (1.32-1.60) were each independently associated with increased risk of death. With further adjustment for FGF23, the risks of death associated with interleukin-6 and C-reactive protein were minimally attenuated. Compared to participants in the lowest quartiles of inflammation and FGF23, the multivariable-adjusted hazard ratio of death among those in the highest quartiles of both biomarkers was 4.38 (2.65-7.23) for interleukin-6 and FGF23, and 5.54 (3.04-10.09) for C-reactive protein and FGF23. Thus, elevated levels of interleukin-6, C-reactive protein, and FGF23 are independent risk factors for mortality in CKD.

Heme Oxygenase 1 Up-Regulates Glomerular Decay Accelerating Factor Expression and Minimizes Complement Deposition and Injury

Complement-activation controllers, including decay accelerating factor (DAF), are gaining emphasis as they minimize injury in various dysregulated complement-activation disorders, including glomerulopathies. Heme oxygenase (HO)-1 overexpression or induction has been shown to attenuate injury in complement-dependent models of glomerulonephritis. This study investigated whether up-regulation of DAF by heme oxygenase 1 (HO-1) is an underlying mechanism by using Hmox-1-deficient rats (Hmox1^+/-; Hmox1^-/-) or rats with HO-1 overexpression targeted to glomerular epithelial cells (GEC^HO-1), which are particularly vulnerable to complement-mediated injury owing to their terminally differentiated nature. Constitutively expressed DAF was decreased in glomeruli of Hmox1^-/- rats and augmented in glomeruli of GEC^HO-1 rats. In GEC^HO-1 rats with anti-glomerular basement membrane antibody mediated, complement-dependent injury, complement component C3 fragment b (C3b) deposition was reduced, whereas proteinuria was diminished. In glomeruli of wild-type rats, the natural Hmox substrate, hemin, induced glomerular DAF. This effect was attenuated in glomeruli of Hmox1^-/- rats and augmented in glomeruli of GEC^HO-1 rats. Hemin analogues differing in either metal or porphyrin ring functionalities, acting as competitive Hmox-substrate inhibitors, also increased glomerular DAF and reduced C3b deposition after spontaneous complement activation. In the presence of a DAF-blocking antibody, the reduction in C3b deposition was reversed. These observations establish HO-1 as a physiologic regulator of glomerular DAF and identify hemin analogues as inducers of functional glomerular DAF able to minimize C3b deposition.

Mitogen-Activated Protein Kinase 14 Promotes AKI

An improved understanding of pathogenic pathways in AKI may identify novel therapeutic approaches. Previously, we conducted unbiased liquid chromatography-tandem mass spectrometry-based protein expression profiling of the renal proteome in mice with acute folate nephropathy. Here, analysis of the dataset identified enrichment of pathways involving NFκB in the kidney cortex, and a targeted data mining approach identified components of the noncanonical NFκB pathway, including the upstream kinase mitogen-activated protein kinase kinase kinase 14 (MAP3K14), the NFκB DNA binding heterodimer RelB/NFκB2, and proteins involved in NFκB2 p100 ubiquitination and proteasomal processing to p52, as upregulated. Immunohistochemistry localized MAP3K14 expression to tubular cells in acute folate nephropathy and human AKI. In vivo, kidney expression levels of NFκB2 p100 and p52 increased rapidly after folic acid injection, as did DNA binding of RelB and NFκB2, detected in nuclei isolated from the kidneys. Compared with wild-type mice, MAP3K14 activity-deficient aly/aly (MAP3K14^aly/aly) mice had less kidney dysfunction, inflammation, and apoptosis in acute folate nephropathy and less kidney dysfunction and a lower mortality rate in cisplatin-induced AKI. The exchange of bone marrow between wild-type and MAP3K14^aly/aly mice did not affect the survival rate of either group after folic acid injection. In cultured tubular cells, MAP3K14 small interfering RNA targeting decreased inflammation and cell death. Additionally, cell culture and in vivo studies identified the chemokines MCP-1, RANTES, and CXCL10 as MAP3K14 targets in tubular cells. In conclusion, MAP3K14 promotes kidney injury through promotion of inflammation and cell death and is a promising novel therapeutic target.

The cytoskeleton as a novel target for treatment of renal fibrosis

The incidence of chronic kidney disease (CKD) is increasing, with an estimated prevalence of 12% in the United States (Synder et al., 2009). While CKD may progress to end-stage renal disease (ESRD), which necessitates renal replacement therapy, i.e. dialysis or transplantation, most CKD patients never reach ESRD due to the increased risk of death from cardiovascular disease. It is well-established that regardless of the initiating insult - most often diabetes or hypertension - fibrosis is the common pathogenic pathway that leads to progressive injury and organ dysfunction (Eddy, 2014; Duffield, 2014). As such, there has been extensive research into the molecular and cellular mechanisms of renal fibrosis; however, translation to effective therapeutic strategies has been limited. While a role for the disruption of the cytoskeleton, most notably the actin network, has been established in acute kidney injury over the past two decades, a role in regulating renal fibrosis and CKD is only recently emerging. This review will focus on the role of the cytoskeleton in regulating pro-fibrotic pathways in the kidney, as well as data suggesting that these pathways represent novel therapeutic targets to manage fibrosis and ultimately CKD.

The epigenetic regulation of the opioid system: new individualized prompt prevention and treatment strategies

The most well-known physiological effect associated with opiod system is their efficacy in pain reduction or analgesia, although their effect on a variety of other physiological and physiophological functions has become apparent in recent years. This review is an attempt to clarify in more detail the epigenetic regulation of opioid system to understand with more precision their transcriptional and posttranscriptional regulation in multiple pyisiological and pharmacological contexts. The opioid receptors show an epigenetic regulation and opioid peptide precursors by methylation, chromatin remodeling and microRNA. Although the opioid receptor promoters have similarity between them, they use different epigenetic regulation forms and they exhibit different pattern of expression during the cell differentiation. DNA methylation is also confirmed in opioid peptide precursors, being important for gene expression and tissue specificity. Understanding the epigenetic basis of those physiological and physiopathological procesess is essential for the development of individualized prompt prevention and treatment strategies.

Podometrics as a Potential Clinical Tool for Glomerular Disease Management

Chronic kidney disease culminating in end-stage kidney disease is a major public health problem costing in excess of $40 billion per year with high morbidity and mortality. Current tools for glomerular disease monitoring lack precision and contribute to poor outcome. The podocyte depletion hypothesis describes the major mechanisms underlying the progression of glomerular diseases, which are responsible for more than 80% of cases of end-stage kidney disease. The question arises of whether this new knowledge can be used to improve outcomes and reduce costs. Podocytes have unique characteristics that make them an attractive monitoring tool. Methodologies for estimating podocyte number, size, density, glomerular volume and other parameters in routine kidney biopsies, and the rate of podocyte detachment from glomeruli into urine (podometrics) now have been developed and validated. They potentially fill important gaps in the glomerular disease monitoring toolbox. The application of these tools to glomerular disease groups shows good correlation with outcome, although data validating their use for individual decision making is not yet available. Given the urgency of the clinical problem, we argue that the time has come to focus on testing these tools for application to individualized clinical decision making toward more effective progression prevention.

Bioinformatics analysis of proteomics profiles in senescent human primary proximal tubule epithelial cells

Background

Dysfunction of renal tubule epithelial cells is associated with renal tubulointerstitial fibrosis. Exploration of the proteomic profiles of senesced tubule epithelial cells is essential to elucidate the mechanism of tubulointerstitium development.

Methods

Primary human proximal tubule epithelial cells from passage 3 (P3) and passage 6 (P6) were selected for evaluation. EdU and SA-β-galactosidase staining were used to detect cell senescence. p53, p21, and p16 were detected by Western blot analysis. Liquid chromatography mass spectrometry (LC-MS) was used to examine differentially expressed proteins (DEPs) between P6 and P3 cells. The expression of DEPs was examined by Western blot analysis. Bioinformatics analysis was performed by protein-protein interaction and gene ontology analyses.

Results

The majority of tubule cells from passage 6 (P6) stained positive for SA-β-galactosidase, whereas passage 3 (P3) cells were negative. Senescence biomarkers, including p53, p21, and p16, were upregulated in P6 cells relative to P3 cells. EdU staining results showed a lower rate of EdU positive cells in P6 cells than in P3 cells. LC-MS was used to examine DEPs between P6 and P3 cells. These DEPs are involved in glycolysis, response to stress, cytoskeleton regulation, oxidative reduction, ATP binding, and oxidative stress. Using Western blot analysis, we validated the down-regulation of AKR1B1, EEF2, EEF1A1, and HSP90 and the up-regulation of VIM in P6 cells seen in the LC-MS data. More importantly, we built the molecular network based on biological functions and protein-protein interactions and found that the DEPs are involved in translation elongation, stress, and glycolysis, and that they are all associated with cytoskeleton regulation, which regulates senescent cell activities such as apoptosis and EMT in tubule epithelial cells.

Conclusions

We explored proteomic profile changes in cell culture-induced senescent cells and built senescence-associated molecular networks, which will help to elucidate the mechanisms of senescence in human proximal tubule epithelial cells.

Aging Biology in the Kidney

The notion that kidney function declines with age in the general population is well known in the Nephrology community and the average loss of glomerular filtration rate (GFR) about 1ml per year in most longitudinal studies. There is much debate within the community about whether this represents "normal aging" or whether this constitutes a form of renal disease. However this debate turns out, the real question is whether this decline is preventable - can it be modified or slowed? Efforts to find drivers of this decline are still in the very earliest stages, but have shown some promise at elucidating some of the pathologies involved. This article will address both the wider issue of the biology of aging as well as the specific pathologies of the aging kidney.

The emerging role of coagulation proteases in kidney disease

A role of coagulation proteases in kidney disease beyond their function in normal haemostasis and thrombosis has long been suspected, and studies performed in the past 15 years have provided novel insights into the mechanisms involved. The expression of protease-activated receptors (PARs) in renal cells provides a molecular link between coagulation proteases and renal cell function and revitalizes research evaluating the role of haemostasis regulators in renal disease. Renal cell-specific expression and activity of coagulation proteases, their regulators and their receptors are dynamically altered during disease processes. Furthermore, renal inflammation and tissue remodelling are not only associated, but are causally linked with altered coagulation activation and protease-dependent signalling. Intriguingly, coagulation proteases signal through more than one receptor or induce formation of receptor complexes in a cell-specific manner, emphasizing context specificity. Understanding these cell-specific signalosomes and their regulation in kidney disease is crucial to unravelling the pathophysiological relevance of coagulation regulators in renal disease. In addition, the clinical availability of small molecule targeted anticoagulants as well as the development of PAR antagonists increases the need for in-depth knowledge of the mechanisms through which coagulation proteases might regulate renal physiology.

Presence of an HO-1 expression threshold in renal glomeruli

This article reports data describing HO-1 expression patterns of heme oxygenase (HO)-1 in isolated rat glomeruli and in cultured glomerular epithelial cells (GEC) in response to its natural substrate heme. Qualitative and quantitative data are presented to support presence of a HO-1 expression threshold in glomeruli but not in GEC. Interpretation of our data and further insight into HO-1 expression pattern in glomeruli may be found in ‘HO-1 expression control in the rat glomerulus’ [1].

Aging in the Canine Kidney

Given the irreversible nature of nephron loss, aging of the kidney is of special interest to diagnostic and toxicologic pathologists. There are many similarities among histologic lesions in aged human and canine kidneys, including increased frequency of glomerulosclerosis, interstitial fibrosis, and tubular atrophy. Unfortunately, there are few studies in which renal tissue from aged healthy dogs was adequately examined with advanced diagnostics—namely, transmission electron microscopy and immunofluorescence—so age-associated changes in canine podocytes and glomerular basement membranes are poorly characterized. An age-associated decrease in the glomerular filtration rate in humans and dogs (specifically small breed dogs) has been documented. Although lesions in aged rats and mice differ somewhat from those of aged dogs and humans, the knowledge gained from rodent models is still vital to elucidating the pathogenesis of age-associated renal disease. Many novel molecules implicated in renal aging have been identified through genetically modified rodent models and transcriptomic and proteomic analysis of human kidneys. These molecules represent intriguing therapeutic targets and diagnostic biomarkers. Likewise, influencing critical pathways of cellular aging, such as telomere shortening, cellular senescence, and autophagy, could improve renal function in the elderly.

Glomerular Aging and Focal Global Glomerulosclerosis: A Podometric Perspective

Kidney aging is associated with an increasing proportion of globally scarred glomeruli, decreasing renal function, and exponentially increasing ESRD prevalence. In model systems, podocyte depletion causes glomerulosclerosis, suggesting age-associated glomerulosclerosis could be caused by a similar mechanism. We measured podocyte number, size, density, and glomerular volume in 89 normal kidney samples from living and deceased kidney donors and normal poles of nephrectomies. Podocyte nuclear density decreased with age due to a combination of decreased podocyte number per glomerulus and increased glomerular volume. Compensatory podocyte cell hypertrophy prevented a change in the proportion of tuft volume occupied by podocytes. Young kidneys had high podocyte reserve (podocyte density >300 per 10(6) µm(3)), but by 70-80 years of age, average podocyte nuclear density decreased to, <100 per 10(6) µm(3), with corresponding podocyte hypertrophy. In older age podocyte detachment rate (urine podocin mRNA-to-creatinine ratio) was higher than at younger ages and podocytes were stressed (increased urine podocin-to-nephrin mRNA ratio). Moreover, in older kidneys, proteinaceous material accumulated in the Bowman space of glomeruli with low podocyte density. In a subset of these glomeruli, mass podocyte detachment events occurred in association with podocytes becoming binucleate (mitotic podocyte catastrophe) and subsequent wrinkling of glomerular capillaries, tuft collapse, and periglomerular fibrosis. In kidneys of young patients with underlying glomerular diseases similar pathologic events were identified in association with focal global glomerulosclerosis. Podocyte density reduction with age may therefore directly lead to focal global glomerulosclerosis, and all progressive glomerular diseases can be considered superimposed accelerators of this underlying process.

Protective role of female gender in programmed accelerated renal aging in the rat

The aging kidney exhibits a progressive decline in glomerular filtration rate, accompanied by inflammatory and oxidative damage. We hypothesized that accelerated, age-related progression of renal injury is ovarian hormones-dependant. To address this we used an established model of developmentally programmed accelerated renal aging in the rat, superimposed by ovariectomy to assess interactions between ovarian hormones and the aging process. Under our experimental conditions, we found that kidney function worsens with age, that is GFR reduces over 18 month analyzed time-course and this was worsened by fetal exposure to maternal low-protein diet and absence of estrogen. Reduction in GFR was followed by increases in albuminuria, proteinuria, inflammatory markers, and tissue carbonyls, all suggesting inflammatory response and oxidative stress. This was associated with changes in AGTR2 expression which was greater at 18 months of age compared to earlier time points, but in MLP offspring only. Our studies show an influence of ovarian hormones on programmed accelerated renal aging and the AGTR2 across the lifespan. The main findings are that ovariectomy is a risk factor for increased aging-related renal injury and that this and oxidative damage might be related to changes in AGTR2 expression.

HO-1 expression control in the rat glomerulus

The differential localization of HO-1 in renal cells under conditions of injury, and the demonstration that exaggerated HO-1 expression can have detrimental rather than beneficial effects, raises the question of whether HO-1 expression in these cells is subject to control. The present study identifies a unique HO-1 expression pattern in the renal glomerulus indicative of presence of HO-1 expression control following prolonged HO-1 induction. HO-1 and HO-2 expression in response to the natural HO substrate/inducer Fe(++) protoporphyrin (PP) IX (hemin) was assessed in normal rat glomeruli. Following 18 h incubations with hemin (0-200 μM), HO-1 expression increased in a concentration-dependent manner and via a hemopexin (HPX) independent mechanism with no effect on HO-2. In incubations with higher hemin concentrations (400 μM), likely to be encountered in hemolytic disorders, HO-1 expression, decreased. This was preceded by a prolonged and sustained increase in HO-1 protein and was independent of the Fe(++) moiety as incubations with Cobalt protoporphyrin (CoPP) resulted in an identical expression pattern. The decrease of HO-1 protein could not be accounted for by proteasomal degradation since it was not reversed in co-incubations with hemin and the proteasome inhibitor, MG132, at concentrations sufficient to increase HO-1 glomerular content when used alone. Moreover, in the presence of MG132, a decrease of HO-1 expression also occurred at 100 and 200 μM hemin. The effect of MG132 was mimicked by two additional mechanistically different approaches which also raised HO-1 content: a) co-incubations of hemin with ZnPP which increased HO-1 protein when used alone, and b) glomerular HO-1 over expression achieved by SB transposon mediated transgenesis. In contrast, the decrease in HO-1 levels observed at high hemin concentrations was reversed in co-incubations with hemin and SnPP, which reduced HO-1 content when used alone. Expression of NF-E2 related factor 2 (Nrf2) protein, which mediates HO-1 induction in response to hemin, had a similar expression pattern with that of HO-1 protein indicating involvement of Nrf2 in the response of HO-1 to hemin. The above observations indicate presence of a HO-1 expression control mechanism in the glomerulus that may serve to protect it against potentially detrimental effects of exaggerated HO-1 expression.

MRTF-A steers an epigenetic complex to activate endothelin-induced pro-inflammatory transcription in vascular smooth muscle cells

Endothelin (ET-1) was initially identified as a potent vasoconstrictor contributing to the maintenance of vascular rhythm. Later studies have implicated ET-1, when aberrantly up-regulated within the vasculature, in a range of human pathologies associated with disruption of vascular homeostasis. ET-1 has been shown to invoke strong pro-inflammatory response in vascular smooth muscle cells (VSMCs); the underlying mechanism, however, remains elusive. Here, we report that the transcriptional modulator MRTF-A mediates the activation of pro-inflammatory mediators by ET-1 in VSMCs. ET-1 increased nuclear enrichment and activity of MRTF-A in cultured VSMCs. MRTF-A silencing attenuated ET-1 induced synthesis and release of pro-inflammatory mediators including IL-6, MCP-1 and IL-1 likely as a result of diminished NF-κB activity. In addition, MRTF-A was indispensible for the accumulation of active histone modifications on the gene promoters. Of intrigue, MRTF-A interacted with and recruited ASH2, a component of the mammalian histone methyltransferase complex, to transactivate pro-inflammatory genes in response to ET-1 treatment. The chromatin remodeling proteins BRG1 and BRM were also required for ET-1-dependent induction of pro-inflammatory mediators by communicating with ASH2, a process dependent on MRTF-A. In conclusion, our data have identified a novel epigenetic complex responsible for vascular inflammation inflicted by ET-1.

Selective anticancer agents suppress aging in Drosophila

Mutations of the PI3K, TOR, iNOS, and NF-κB genes increase lifespan of model organisms and reduce the risk of some aging-associated diseases. We studied the effects of inhibitors of PI3K (wortmannin), TOR (rapamycin), iNOS (1400W), NF-κB (pyrrolidin dithiocarbamate and QNZ), and the combined effects of inhibitors: PI3K (wortmannin) and TOR (rapamycin), NF-κB (pyrrolidin dithiocarbamates) and PI3K (wortmannin), NF-κB (pyrrolidine dithiocarbamates) and TOR (rapamycin) on Drosophila melanogaster lifespan and quality of life (locomotor activity and fertility). Our data demonstrate that pharmacological inhibition of PI3K, TOR, NF-κB, and iNOS increases lifespan of Drosophila without decreasing quality of life. The greatest lifespan expanding effect was achieved by a combination of rapamycin (5 μM) and wortmannin (5 μM) (by 23.4%). The bioinformatic analysis (KEGG, REACTOME.PATH, DOLite, and GO.BP) showed the greatest aging-suppressor activity of rapamycin, consistent with experimental data.

Epigenetics of progression of chronic kidney disease: fact or fantasy?

Epigenetic modifications are important in the normal functioning of the cell, from regulating dynamic expression of essential genes and associated proteins to repressing those that are unneeded. Epigenetic changes are essential for development and functioning of the kidney, and aberrant methylation, histone modifications, and expression of microRNA could lead to chronic kidney disease (CKD). Here, epigenetic modifications modulate transforming growth factor β signaling, inflammation, profibrotic genes, and the epithelial-to-mesenchymal transition, promoting renal fibrosis and progression of CKD. Identification of these epigenetic changes is important because they are potentially reversible and may serve as therapeutic targets in the future to prevent subsequent renal fibrosis and CKD. In this review we discuss the different types of epigenetic control, methods to study epigenetic modifications, and how epigenetics promotes progression of CKD.

Direct action of endothelin-1 on podocytes promotes diabetic glomerulosclerosis

The endothelin system has emerged as a novel target for the treatment of diabetic nephropathy. Endothelin-1 promotes mesangial cell proliferation and sclerosis. However, no direct pathogenic effect of endothelin-1 on podocytes has been shown in vivo and endothelin-1 signaling in podocytes has not been investigated. This study investigated endothelin effects in podocytes during experimental diabetic nephropathy. Stimulation of primary mouse podocytes with endothelin-1 elicited rapid calcium transients mediated by endothelin type A receptors (ETARs) and endothelin type B receptors (ETBRs). We then generated mice with a podocyte-specific double deletion of ETAR and ETBR (NPHS2-Cre×Ednra(lox/lox)×Ednrb(lox/lox) [Pod-ETRKO]). In vitro, treatment with endothelin-1 increased total β-catenin and phospho-NF-κB expression in wild-type glomeruli, but this effect was attenuated in Pod-ETRKO glomeruli. After streptozotocin injection to induce diabetes, wild-type mice developed mild diabetic nephropathy with microalbuminuria, mesangial matrix expansion, glomerular basement membrane thickening, and podocyte loss, whereas Pod-ETRKO mice presented less albuminuria and were completely protected from glomerulosclerosis and podocyte loss, even when uninephrectomized. Moreover, glomeruli from normal and diabetic Pod-ETRKO mice expressed substantially less total β-catenin and phospho-NF-κB compared with glomeruli from counterpart wild-type mice. This evidence suggests that endothelin-1 drives development of glomerulosclerosis and podocyte loss through direct activation of endothelin receptors and NF-κB and β-catenin pathways in podocytes. Notably, both the expression and function of the ETBR subtype were found to be important. Furthermore, these results indicate that activation of the endothelin-1 pathways selectively in podocytes mediates pathophysiologic crosstalk that influences mesangial architecture and sclerosis.

Slowing the aging process

Research into the aging process is very new. For many years aging was thought to be the natural and inevitable consequence of a life of wear and tear. The idea that aging could be influenced by the genetic code and had a modifiable biologic component is less than 20 years old. During this time, aging has come to be understood as a complex biologic process controlled by signaling pathways and transcription factors. Similar attitudes pervade the field of nephrology. Whether a decline in renal function with age represents normal aging or kidney disease is the subject of much debate.

The aging kidney revisited: a systematic review

As for the whole human body, the kidney undergoes age-related changes which translate in an inexorable and progressive decline in renal function. Renal aging is a multifactorial process where gender, race and genetic background and several key-mediators such as chronic inflammation, oxidative stress, the renin-angiotensin-aldosterone (RAAS) system, impairment in kidney repair capacities and background cardiovascular disease play a significant role. Features of the aging kidney include macroscopic and microscopic changes and important functional adaptations, none of which is pathognomonic of aging. The assessment of renal function in the framework of aging is problematic and the question whether renal aging should be considered as a physiological or pathological process remains a much debated issue. Although promising dietary and pharmacological approaches have been tested to retard aging processes or renal function decline in the elderly, proper lifestyle modifications, as those applicable to the general population, currently represent the most plausible approach to maintain kidney health.

Plasma ceruloplasmin, a regulator of nitric oxide activity, and incident cardiovascular risk in patients with CKD

BACKGROUND AND OBJECTIVES

Increased serum levels of the acute-phase reactant ceruloplasmin predict adverse clinical outcomes in the setting of acute coronary syndromes and heart failure, but their role in patients with CKD is unclear. This study investigated the relationship of ceruloplasmin with clinical outcomes in CKD, especially with regard to traditional cardiac biomarkers.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Serum ceruloplasmin levels in consecutive study participants with CKD (n=654; estimated GFR<60 ml/min per 1.73 m(2)) as well as a control group of non-CKD participants matched for age and sex (n=250) were measured. Study participants were enrolled during 2001-2006 from a population of patients presenting for elective diagnostic coronary angiography and prospectively followed for 3 years (median follow-up=1095 days) to determine incident major adverse cardiac events (defined as a composite of death, nonfatal myocardial infarction, and stroke).

RESULTS

Serum ceruloplasmin levels in CKD patients were elevated versus controls (median [interquartile range]; 25.5 [21.8-29.6] versus 22.7 [19.7-26.5] mg/dl; P<0.001) and associated with increased risk of future major adverse cardiac events (hazard ratio, 1.35; 95% confidence interval, 1.0 to 1.82; P=0.04). After adjusting for traditional risk factors, higher serum ceruloplasmin was still associated with higher risk of major adverse cardiac events at 3 years (hazard ratio, 1.61; 95% confidence interval, 1.15 to 2.25; P=0.01).

CONCLUSION

In CKD patients, increased serum ceruloplasmin, a regulator of nitric oxide activity, is associated with increased risk of long-term adverse cardiovascular events, even after multivariable model adjustment for traditional clinical and biologic risk factors.

Nonsteroidal anti-inflammatory drug induces proinflammatory damage in gastric mucosa through NF-κB activation and neutrophil infiltration: anti-inflammatory role of heme oxygenase-1 against nonsteroidal anti-inflammatory drug

Nonsteroidal anti-inflammatory drug (NSAID)-induced mitochondrial oxidative stress (MOS) is an important prostaglandin (PG)-independent pathway of the induction of gastric mucosal injury. However, the molecular mechanism behind MOS-mediated gastric pathology is still obscure. In various pathological conditions of tissue injury oxidative stress is often linked with inflammation. Here we report that MOS induced by indomethacin (an NSAID) induces gastric mucosal inflammation leading to proinflammatory damage. Indomethacin, time dependently stimulated the expression of proinflammatory molecules such as intercellular adhesion molecule 1(ICAM-1), vascular cell adhesion molecule 1(VCAM-1), interleukin1β (IL-1β), and monocyte chemotactic protein-1 (MCP-1) in gastric mucosa in parallel with the increase of neutrophil infiltration and injury of gastric mucosa in rat. Western immunoblotting and confocal microscopic studies revealed that indomethacin induced nuclear translocation of nuclear factor kappa-B (NF-κB) in gastric mucosal cells, which resulted in proinflammatory signaling. The prevention of MOS by antioxidant tryptamine-gallic acid hybrid (SEGA) inhibited indomethacin-induced expression of ICAM-1, VCAM-1, IL-1β, and MCP-1. SEGA also prevented indomethacin-induced NF-κB activation and neutrophil infiltration as documented by chromatin immunoprecipitation studies and neutrophil migration assay, respectively. Heme oxygenase-1 (HO-1), a cytoprotective enzyme associated with tissue repair mechanisms is stimulated in response to oxidative stress. We have investigated the role of HO-1 against MOS and MOS-mediated inflammation in recovering from gastropathy. Indomethacin stimulated the expression of HO-1 and indomethacin-stimulated HO-1 expression was reduced by SEGA, an antioxidant, which could prevent MOS. Thus, the data suggested that the induction of HO-1 was a protective response against MOS developed by indomethacin. Moreover, the induction of HO-1 by cobalt protoporphyrin inhibited inflammation and chemical silencing of HO-1 by zinc protoporphyrin aggravated the inflammation by indomethacin. Thus, NSAID by promoting MOS-induced proinflammatory response damaged gastric mucosa and HO-1 protected NSAID-induced gastric mucosal damage by preventing NF-κB activation and proinflammatory activity.

Functions of the podocyte proteins nephrin and Neph3 and the transcriptional regulation of their genes

Nephrin and Neph-family proteins [Neph1–3 (nephrin-like 1–3)] belong to the immunoglobulin superfamily of cell-adhesion receptors and are expressed in the glomerular podocytes. Both nephrin and Neph-family members function in cell adhesion and signalling, and thus regulate the structure and function of podocytes and maintain normal glomerular ultrafiltration. The expression of nephrin and Neph3 is altered in human proteinuric diseases emphasizing the importance of studying the transcriptional regulation of the nephrin and Neph3 genes NPHS1 (nephrosis 1, congenital, Finnish type) and KIRREL2 (kin of IRRE-like 2) respectively. The nephrin and Neph3 genes form a bidirectional gene pair, and they share transcriptional regulatory mechanisms. In the present review, we summarize the current knowledge of the functions of nephrin and Neph-family proteins and transcription factors and agents that control nephrin and Neph3 gene expression.

Urine podocyte mRNAs, proteinuria, and progression in human glomerular diseases

Model systems demonstrate that progression to ESRD is driven by progressive podocyte depletion (the podocyte depletion hypothesis) and can be noninvasively monitored through measurement of urine pellet podocyte mRNAs. To test these concepts in humans, we analyzed urine pellet mRNAs from 358 adult and pediatric kidney clinic patients and 291 controls (n=1143 samples). Compared with controls, urine podocyte mRNAs increased 79-fold (P<0.001) in patients with biopsy-proven glomerular disease and a 50% decrease in kidney function or progression to ESRD. An independent cohort of patients with Alport syndrome had a 23-fold increase in urinary podocyte mRNAs (P<0.001 compared with controls). Urinary podocyte mRNAs increased during active disease but returned to baseline on disease remission. Furthermore, urine podocyte mRNAs increased in all categories of glomerular disease evaluated, but levels ranged from high to normal, consistent with individual patient variability in the risk for progression. In contrast, urine podocyte mRNAs did not increase in polycystic kidney disease. The association between proteinuria and podocyturia varied markedly by glomerular disease type: a high correlation in minimal-change disease and a low correlation in membranous nephropathy. These data support the podocyte depletion hypothesis as the mechanism driving progression in all human glomerular diseases, suggest that urine pellet podocyte mRNAs could be useful for monitoring risk for progression and response to treatment, and provide novel insights into glomerular disease pathophysiology.

Fn14 in podocytes and proteinuric kidney disease

Non-proliferative proteinuric diseases are the most common primary glomerular disorders causing end-stage renal disease. These disorders may associate low level glomerular inflammation and podocyte expression of inflammatory mediators. However, the factors regulating podocyte expression of inflammatory mediators in vivo in non-immune disorders are poorly understood. We have now explored the regulation and role of TWEAK receptor Fn14 in mediating glomerular inflammation in cultured podocytes and in experimental and human non-immune proteinuria. Transcriptomics disclosed Fn14 and MCP-1 mRNA upregulation in glomeruli from patients with focal segmental glomerulosclerosis, as well as a correlation between the expression of both transcripts. Increased glomerular Fn14 and MCP-1 mRNA was confirmed in a second focal segmental glomerulosclerosis cohort and was also observed in membranous nephropathy. In human non-proliferative proteinuric kidney diseases podocytes displayed Fn14 and MCP-1 expression and NFκB activation. Podocyte Fn14 was increased in murine protein overload-induced proteinuria. In Fn14 knock-out mice with protein overload-induced proteinuria, glomerular and periglomerular macrophage infiltrates were reduced, as were MCP-1 mRNA and podocyte MCP-1 staining and podocyte numbers preserved as compared to wild-type counterparts. Adenovirus-mediated overexpression of TWEAK increased periglomerular macrophage infiltration in mice without prior kidney injury. In cultured podocytes inflammatory cytokines increased Fn14 mRNA and protein levels. TWEAK activated NFκB and increased MCP-1 mRNA and protein, an effect prevented by the NFκB inhibitor parthenolide. In conclusion, Fn14 activation results in NFκB-mediated pro-inflammatory effects on podocytes that may be relevant for the pathogenesis of non-proliferative proteinuric kidney disease of non-immune origin.

Molecular events in matrix protein metabolism in the aging kidney

We explored molecular events associated with aging-induced matrix changes in the kidney. C57BL6 mice were studied in youth, middle age, and old age. Albuminuria and serum cystatin C level (an index of glomerular filtration) increased with aging. Renal hypertrophy was evident in middle-aged and old mice and was associated with glomerulomegaly and increase in mesangial fraction occupied by extracellular matrix. Content of collagen types I and III and fibronectin was increased with aging; increment in their mRNA varied with the phase of aging. The content of ZEB1 and ZEB2, collagen type I transcription inhibitors, and their binding to the collagen type Iα2 promoter by ChIP assay also showed age-phase-specific changes. Lack of increase in mRNA and data from polysome assay suggested decreased degradation as a potential mechanism for kidney collagen type I accumulation in the middle-aged mice. These changes occurred with increment in TGFβ mRNA and protein and activation of its SMAD3 pathway; SMAD3 binding to the collagen type Iα2 promoter was also increased. TGFβ-regulated microRNAs (miRs) exhibited selective regulation. The renal cortical content of miR-21 and miR-200c, but not miR-192, miR-200a, or miR-200b, was increased with aging. Increased miR-21 and miR-200c contents were associated with reduced expression of their targets, Sprouty-1 and ZEB2, respectively. These data show that aging is associated with complex molecular events in the kidney that are already evident in the middle age and progress to old age. Age-phase-specific regulation of matrix protein synthesis occurs and involves matrix protein-specific transcriptional and post-transcriptional mechanisms.