[Abstract unavailable

Relaxin is a potent inhibitor of TGF-beta1-induced extracellular matrix (ECM) synthesis and secretion as well as fibroblast activation. Furthermore, it induces ECM degradation by induction of MMP-2 and MMP-9. These effects are mediated, at least in part, by inhibition of TGF-beta1 signaling.

Excessive TGF-b signaling in epithelial cells, pericytes, or fibroblasts has been implicated in CKD. This list has recently been joined by endothelial cells (ECs) undergoing mesenchymal transition. Although several studies focused on the effects of ablating epithelial or fibroblast TGF-b signaling on development of fibrosis, there is a lack of information on ablating TGF-b signaling in the endothelium because this ablation causes embryonic lethality. We generated endothelium-specific heterozygous TGF-b receptor knockout (TbRII endo+/2 ) mice to explore whether curtailed TGF-b signaling significantly modifies nephrosclerosis.These mice developed normally, but showed enhanced angiogenic potential compared with TbRII endo+/+ mice under basal conditions. After induction of folic acid nephropathy or unilateral ureteral obstruction, TbRII endo+/2 mice exhibited less tubulointerstitial fibrosis, enhanced preservation of renal microvasculature, improvement in renal blood flow, and less tissue hypoxia than TbRII endo+/+ counterparts. In addition, partial deletion of TbRII in the endothelium reduced endothelial-to-mesenchymal transition (EndoMT). TGF-b-induced canonical Smad2 signaling was reduced in TbRII +/2 ECs; however, activin receptor-like kinase 1 (ALK1)-mediated Smad1/5 phosphorylation in TbRII +/2 ECs remained unaffected. Furthermore, the S-endoglin/L-endoglin mRNA expression ratio was significantly lower in TbRII +/2 ECs compared with TbRII +/+ ECs. These observations support the hypothesis that EndoMT contributes to renal fibrosis and curtailing endothelial TGF-b signals favors Smad1/5 proangiogenic programs and dictates increased angiogenic responses. Our data implicate endothelial TGF-b signaling and EndoMT in regulating angiogenic and fibrotic responses to injury.

High mobility group box 1 (HMGB1) undergoes acetylation, nuclear-to-cytoplasmic translocation and release from stressed kidneys, unleashing a signaling cascade of events leading to systemic inflammation. Here we tested whether the deacetylase activity of Sirtuin1 (SIRT1) participates in regulating nuclear retention of HMGB1 to ultimately modulate damage signaling initiated by HMGB1 secretion during stress. When immunoprecipitated acetylated HMGB1 was incubated with SIRT1, HMGB1 acetylation decreased by 57%. Proteomic analysis showed that SIRT1 deacetylates HMGB1 at four lysine residues (55, 88, 90 and 177) within the pro-inflammatory and nuclear localization signal domains of HMGB1. Genetic ablation or pharmacological inhibition of SIRT1 in endothelial cells increased HMGB1 acetylation and translocation. In vivo, deletion of SIRT1 reduced nuclear HMGB1 while increasing its acetylation and release into circulation during basal and ischemic conditions causing increased renal damage. Conversely, resveratrol pretreatment led to decreased HMGB1 acetylation, its nuclear retention, decreased systemic release and reduced tubular damage. Thus, a vicious cycle is set into motion in which the inflammation-induced repression of SIRT1 disables deacetylation of HMGB1, facilitates its nuclear-to-cytoplasmic translocation and systemic release, thereby maintaining inflammation.

Sirtuin 1 (SIRT1) depletion in vascular endothelial cells mediates endothelial dysfunction and premature senescence in diverse cardiovascular and renal diseases. However, the molecular mechanisms underlying these pathologic effects remain unclear. Here, we examined the phenotype of a mouse model of vascular senescence created by genetically ablating exon 4 of Sirt1 in endothelial cells (Sirt1 endo2/2 ). Under basal conditions, Sirt1 endo2/2 mice showed impaired endothelium-dependent vasorelaxation and angiogenesis, and fibrosis occurred spontaneously at low levels at an early age. In contrast, induction of nephrotoxic stress (acute and chronic folic acid-induced nephropathy) in Sirt1 endo2/2 mice resulted in robust acute renal functional deterioration followed by an exaggerated fibrotic response compared with control animals. Additional studies identified matrix metalloproteinase-14 (MMP-14) as a target of SIRT1. In the kidneys of Sirt1 endo2/2 mice, impaired angiogenesis, reduced matrilytic activity, and retention of the profibrotic cleavage substrates tissue transglutaminase and endoglin accompanied MMP-14 suppression. Furthermore, restoration of MMP-14 expression in SIRT1-depeleted mice improved angiogenic and matrilytic functions of the endothelium, prevented renal dysfunction, and attenuated nephrosclerosis. Our findings establish a novel mechanistic molecular link between endothelial SIRT1 depletion, downregulation of MMP-14, and the development of nephrosclerosis.

The list of signals sent by an injured organ to systemic circulation, so-called danger signals, is growing to include multiple metabolites and secreted moieties, thus revealing a highly complex and integrated network of interlinked systemic proinflammatory and proregenerative messages. Emerging new data indicate that, apart from the well established local inflammatory response to AKI, danger signaling unleashes a cascade of precisely timed, interdependent, and intensity-gradated mediators responsible for development of the systemic inflammatory response. This fledgling realization of the importance of the systemic inflammatory response to the localized injury and inflammation is at the core of this brief overview. It has a potential to explain the additive effects of concomitant diseases or preexisting chronic conditions that can prime the systemic inflammatory response and exacerbate it out of proportion to the actual degree of acute kidney damage. Although therapies for ameliorating AKI per se remain limited, a potentially powerful strategy that could reap significant benefits in the future is to modulate the intensity of danger signals and consequently the systemic inflammatory response, while preserving its intrinsic proregenerative stimuli.

BackgroundAim of this single center cross-sectional study was to investigate oral behavior, dental, periodontal and microbiological findings in patients undergoing hemodialysis (HD) and after kidney transplantation (KT).MethodsPatients undergoing HD for end-stage renal failure and after KT were investigated. Oral health behavior was recorded using a standardized questionnaire, e.g. dental behavior, tooth brushing, oral hygiene aids. Oral investigation included screening of oral mucosa, dental findings (DMF-T) and periodontal situation (Papilla bleeding index [PBI] periodontal probing depth [PPD] and clinical attachment loss [CAL]). Additionally, microbiological analysis of subgingival biofilm samples (PCR) was performed. Statistical analysis: Student’s t-test or Mann–Whitney-U-test, Fisher’s exact test (α = 5 %).ResultsA total of 70 patients (HD: n = 35, KT: n = 35) with a mean age of 56.4 ± 11.1 (HD) and 55.8 ± 10.9 (KT) years were included. Lack in use of additional oral hygiene (dental floss, inter-dental brush) was found. KT group presented significantly more gingivial overgrowth (p = 0.01). DMF-T was 19.47 ± 5.84 (HD) and 17.61 ± 5.81 (KT; p = 0.21). Majority of patients had clinically moderate and severe periodontitis; showing a need for periodontal treatment of 57 % (HD) and 71 % (KT; p = 0.30). Significantly higher prevalence of Parvimonas micra and Capnocytophaga species in the HD group were found (p < 0.01).ConclusionPeriodontal treatment need and lack in oral behavior for both groups indicate the necessity of an improved early treatment and prevention of dental and periodontal disease, e.g. in form of special care programs. Regarding microbiological findings, no major differences between KT and HD patients were found.

SummaryRenal fibrosis is characterized by excessive accumulation of extracellular matrix (ECM), which compromises organ function by replacing normal organ tissue. The molecular mechanisms leading to renal fibrosis are not fully understood. Here we demonstrated that TGFb1, AGT or PDGF stimulation of renal cells resulted in endoplasmic reticulum (ER) stress followed by activation of the protective unfolded protein response pathway and a high secretory level of protein disulfide isomerase ERP57 (also known as PDIA3). The TGFb1-induced impairment of ER function could be reversed by treatment with BMP7, suggesting a specific involvement in renal fibrosis. A clear correlation between the degree of fibrosis, ER stress and the level of ERP57 could be seen in fibrosis animal models and in biopsies of renal fibrosis patients. Protein interaction studies revealed that secreted ERP57 exhibits a strong interaction with ECM proteins. Knockdown of ERP57 or antibody-targeted inhibition of the secreted form significantly impaired the secretion and accumulation of ECM. Moreover, ERP57 was excreted in the early stages of chronic kidney disease, and its level in urine correlated with the degree of renal fibrosis, suggesting that the secretion of ERP57 represents one of the first signs of renal fibrosis onset and progression.