Bioactive peptides control receptor for advanced glycated end product-induced elevation of kidney insulin receptor substrate 2 and reduce albuminuria in diabetic mice

Mitochondrial Peptide Humanin Protects Silver Nanoparticles-Induced Neurotoxicity in Human Neuroblastoma Cancer Cells (SH-SY5Y)

The extensive usage of silver nanoparticles (AgNPs) as medical products such as antimicrobial and anticancer agents has raised concerns about their harmful effects on human beings. AgNPs can potentially induce oxidative stress and apoptosis in cells. However, humanin (HN) is a small secreted peptide that has cytoprotective and neuroprotective cellular effects. The aim of this study was to assess the harmful effects of AgNPs on human neuroblastoma SH-SY5Y cells and also to investigate the protective effect of HN from AgNPs-induced cell death, mitochondrial dysfunctions, DNA damage, and apoptosis. AgNPs were prepared with an average size of 18 nm diameter to study their interaction with SH-SY5Y cells. AgNPs caused a dose-dependent decrease of cell viability and proliferation, induced loss of plasma-membrane integrity, oxidative stress, loss of mitochondrial membrane potential (MMP), and loss of ATP content, amongst other effects. Pretreatment or co-treatment of HN with AgNPs protected cells from several of these AgNPs induced adverse effects. Thus, this study demonstrated for the first time that HN protected neuroblastoma cells against AgNPs-induced neurotoxicity. The mechanisms of the HN-mediated protective effect on neuroblastoma cells may provide further insights for the development of novel therapeutic agents against neurodegenerative diseases.

Humanin and age-related diseases: a new link?

Humanin (HN) is 24-amino acid mitochondria-associated peptide. Since its initial discovery over a decade ago, a role for HN has been reported in many biological processes such as apoptosis, cell survival, substrate metabolism, inflammatory response, and response to stressors such as oxidative stress, ischemia, and starvation. HN and its potent analogs have been shown to have beneficial effects in many age-related diseases including Alzheimer's disease, stroke, diabetes, myocardial ischemia and reperfusion, atherosclerosis, amyotrophic lateral sclerosis, and certain types of cancer both in vitro and in vivo. More recently, an association between HN levels, growth hormone/insulin-like growth factor-1 (GH/IGF axis), and life span was demonstrated using various mouse models with mutations in the GH/IGF axis. The goal of this review is to summarize the current understanding of the role of HN in aging and age-related diseases.

Pharmacokinetics and tissue distribution of humanin and its analogues in male rodents

Humanin (HN) is a novel 24-amino acid mitochondrial-derived peptide that has demonstrated diverse cytoprotective effects, including an emerging role in diabetes. The purpose of this study was to examine the pharmacokinetics of humanin analogues, which show great potential as therapeutic agents (HNG and the non-IGFBP-3 binding, HNGF6A). 11-week-old male IGFBP-3(-/-) and wild type (WT) mice were divided into 3 groups: WT mice treated with HNG, WT mice treated with HNGF6A, and IGFBP-3(-/-) mice treated with HNG. Plasma was obtained from mice following ip injection with HN analogues, and HN levels were measured with ELISA. WT mice treated with HNGF6A and IGFBP-3(-/-) mice treated with HNG displayed a longer half-life of HN compared with WT mice treated with HNG. Following HNG injection, both IGF-1 and IGFBP-3 levels decreased over time. Adult male Sprague Dawley rats were also ip injected with HNG, and HN levels were measured in various tissues (plasma, liver, heart, and brain) by ELISA. The half-life of HN was found to be longer in rats compared with mice. In rats, HN levels were found to be highest in plasma, present in liver, and undetectable in brain or heart. The current study provides evidence of HN and IGFBP-3 association in the circulation and suggests that native HN may modulate the distribution of IGF-1 and IGFBP-3. The results also demonstrate varying kinetic profiles of HN analogues and interspecies variation in rodents. Sustainable levels of circulating HN measured in plasma underline the potential value of HN analogues as a new therapeutic intervention in the treatment of diabetes.

The myofibroblast matrix: implications for tissue repair and fibrosis

Myofibroblasts, and the extracellular matrix (ECM) in which they reside, are critical components of wound healing and fibrosis. The ECM, traditionally viewed as the structural elements within which cells reside, is actually a functional tissue whose components possess not only scaffolding characteristics, but also growth factor, mitogenic, and other bioactive properties. Although it has been suggested that tissue fibrosis simply reflects an 'exuberant' wound-healing response, examination of the ECM and the roles of myofibroblasts during fibrogenesis instead suggest that the organism may be attempting to recapitulate developmental programmes designed to regenerate functional tissue. Evidence of this is provided by the temporospatial re-emergence of embryonic ECM proteins by fibroblasts and myofibroblasts that induce cellular programmatic responses intended to produce a functional tissue. In the setting of wound healing (or physiological fibrosis), this occurs in a highly regulated and exquisitely choreographed fashion which results in cessation of haemorrhage, restoration of barrier integrity, and re-establishment of tissue function. However, pathological tissue fibrosis, which oftentimes causes organ dysfunction and significant morbidity or mortality, likely results from dysregulation of normal wound-healing processes or abnormalities of the process itself. This review will focus on the myofibroblast ECM and its role in both physiological and pathological fibrosis, and will discuss the potential for therapeutically targeting ECM proteins for treatment of fibrotic disorders.

Mammalian target of rapamycin complex 2 regulates inflammatory response to stress

OBJECTIVE AND DESIGN

To explore the role of mammalian target of rapamycin 2 (mTORC2) in the activation of inflammatory and oxidative responses in rodent models of acute injury and metabolic stress.

MATERIAL

The impact of nephrilin, an inhibitor of mTORC2 complex, was assessed in three CD-1 mouse models of acute xenobiotic stress and in a hypertensive Dahl rat model of metabolic stress.

METHODS

Animals received daily subcutaneous bolus injections of saline or 4 mg/kg nephrilin. Tissues were assayed by ELISA, gene arrays and immunohistochemical staining.

RESULTS

Nephrilin significantly inhibited elevations in plasma tumor necrosis factor-alpha, kidney substance P, and CX3CR1, and urinary lipocalin-2 [urinary neutrophil gelatinase-associated lipocalin (uNGAL)] in models of acute xenobiotic stress. UCHL1 gene expression levels dropped and plasma HMGB1 levels rose in the rhabdomyolysis model. Both effects were reversed by nephrilin. The inhibitor also blocked diet-induced elevations of uNGAL and albumin-creatinine ratio (UACR) as well as kidney tissue phosphorylation of PKC-beta-2-T641 and p66shc-S36, and reduced dark ring-like staining of nuclei by anti-phos-p66shc-S36 antibody in frozen sections of diseased kidneys from hypertensive Dahl rats fed an 8 % NaCl diet for 4 weeks.

CONCLUSIONS

Taken together, our results suggest a role for mTORC2 in the inflammatory-oxidative responses to stress.

Regulation of heparanase by albumin and advanced glycation end products in proximal tubular cells

Diabetic nephropathy is one of the main causes of end-stage renal disease, in which the development of tubular damage depends on factors such as high glucose levels, albuminuria and advanced glycation end-product. In this study, we analyzed the involvement of heparanase, a heparan sulfate glycosidase, in the homeostasis of proximal tubular epithelial cells in the diabetic milieu. In vitro studies were performed on a wild-type and stably heparanase-silenced adult tubular line (HK2) and HEK293. Gene and protein expression analyses were performed in the presence and absence of diabetic mediators. Albumin and advanced glycation end-product, but not high glucose levels, increased heparanase expression in adult tubular cells via the AKT/PI3K signaling pathway. This over-expression of heparanase is then responsible for heparan sulfate reduction via its endoglycosidase activity and its capacity to regulate the heparan sulfate-proteoglycans core protein. In fact, heparanase regulates the gene expression of syndecan-1, the most abundant heparan sulfate-proteoglycans in tubular cells. We showed that heparanase is a target gene of the diabetic nephropathy mediators albumin and advanced glycation end-product, so it may be relevant to the progression of diabetic nephropathy. It could take part in several processes, e.g. extracellular-matrix remodeling and cell-cell crosstalk, via its heparan sulfate endoglycosidase activity and capacity to regulate the expression of the heparan sulfate-proteoglycan syndecan-1.

A nuclear complex of rictor and insulin receptor substrate-2 is associated with albuminuria in diabetic mice

BACKGROUND

Signaling events associated with diabetic nephropathy are not well understood. Triangulation of events triggered by unrelated bioactive peptides nephrilin and anephril, both of which inhibit albuminuria in diabetic mice, could reveal a common subset of events associated with albuminuria.

METHODS

db/db mice received 20 microg/day anephril or nephrilin for 7 weeks. Streptozotocin (STZ)-treated DBA/2J mice received 2 mg/kg nephrilin for 26 days. In both studies, urine albumin and creatinine, plasma glucose, and tissue proteins were measured by enzyme-linked immunosorbent assay (ELISA). In a safety study, DBA/2J mice received 20 mg/kg nephrilin for 26 days, and tissues from these mice were fixed in formalin for histological analysis. HEK293 human kidney cells were treated with glycated hemoglobin plus 20 microg/mL nephrilin or anephril for 24 h.

RESULTS

Both peptides reduced albuminuria in db/db mice compared to saline-treated animals without affecting plasma glucose or insulin. In kidney tissues, the immunoreactivities of insulin receptor substrate-2 (IRS2), phosphorylated protein kinase C (p-PKC), and serum- and glucocortocoid-inducible kinase (SGK1) were reduced. Nephrilin, but not anephril, lowered elevated SGK1 in spleens of db/db mice. In STZ-pretreated DBA/2J mice, nephrilin reduced albuminuria and the accumulation of nuclear Rictor, IRS2, and p-PKC in the kidney. In cultured kidney cells, nephrilin disrupted the association of Rictor with IRS2 and nuclear compartmentalization. Histopathological examination of tissues from mice treated with 20 mg/kg nephrilin daily for 26 days showed no significant pathology compared to saline-treated controls.

CONCLUSIONS

We define a subset of signaling markers closely associated with albuminuria. Mammalian target of rapamycin complex 2 (mTORC2)::IRS complexes may play a role in the nuclear accumulation, and possible downstream transcriptional effects, of p-PKC. The activity and apparent safety of nephrilin in rodents suggest a novel intervention strategy for diabetic kidney disease.