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Proteinuria and hyperglycemia induce endoplasmic reticulum stress.

ABSTRACT: The endoplasmic reticulum (ER) is an important site for protein folding and becomes "stressed" when its capacity to fold proteins is overwhelmed. In response, "unfolded protein response" (UPR) genes are induced, increasing the capacity to fold proteins; if the response is insufficient, then apoptosis ensues. For investigation of whether proteinuria and hyperglycemia induce ER stress in renal epithelial cells, microarray data from biopsies of established diabetic nephropathy (DN) were analyzed. Expression of UPR genes was significantly different in these biopsies than in control kidneys or biopsies of patients with mild DN, suggesting an association between the degree of DN and UPR gene expression. Expression of the transcription factor XBP1 and the ER chaperones HSPA5 and HYOU1 were increased, but the proapoptotic gene DDIT3 was unchanged. These findings were replicated in an independent cohort of patients with established DN by real-time reverse transcriptase-PCR. Immunofluorescence of renal biopsies from patients with DN confirmed the upregulation for HSPA5 and HYOU1 proteins in tubular epithelia. In biopsies of minimal-change disease, the mRNA levels of some ER stress molecules were also induced, but protein expression of HSPA5 and HYOU1 remained significantly lower than that observed in DN. Exposure of renal tubular epithelial cells to albumin and high glucose in vitro enhanced expression of genes involved in ER stress. These observations suggest that in proteinuric diseases, tubular epithelial cells undergo ER stress, which induces an adaptive, protective UPR. Although this may protect the cells from ER stress, persistence of hyperglycemia and proteinuria may eventually lead to apoptosis.

SUBMITTER: Lindenmeyer MT

PROVIDER: S-EPMC2573014 | biostudies-literature | 2008 Nov

REPOSITORIES: biostudies-literature

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Proteinuria and hyperglycemia induce endoplasmic reticulum stress.

Lindenmeyer Maja T MT Rastaldi Maria P MP Ikehata Masami M Neusser Matthias A MA Kretzler Matthias M Cohen Clemens D CD Schlöndorff Detlef D

Journal of the American Society of Nephrology : JASN 20080905 11

The endoplasmic reticulum (ER) is an important site for protein folding and becomes "stressed" when its capacity to fold proteins is overwhelmed. In response, "unfolded protein response" (UPR) genes are induced, increasing the capacity to fold proteins; if the response is insufficient, then apoptosis ensues. For investigation of whether proteinuria and hyperglycemia induce ER stress in renal epithelial cells, microarray data from biopsies of established diabetic nephropathy (DN) were analyzed. E ...[more]

PMID: 18776125

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Project description:BACKGROUND:Silicon dioxide nanoparticles (SiO2 NPs) are one of the most widely utilized NPs in various food sectors. However, the potential endocrine toxicity of SiO2 NPs has not been characterized. RESULTS:In the present study, mice were orally administered a series of doses of SiO2 NPs. All doses of SiO2 NPs were absorbed into the blood, liver, and pancreas of the mice. Administration of 100 mg/kg bw (body weight) of SiO2 NPs significantly increased blood glucose levels in mice. However, the same dose of SiO2 fine-particles (FPs) did not result in altered blood glucose. Whole-genome analysis showed that SiO2 NPs affected the expression of genes associated with reactive oxygen species (ROS) production and endoplasmic reticulum (ER) stress. In addition, we showed that SiO2 NPs activated xenobiotic metabolism, resulting in ER stress. Endoplasmic reticulum stress resulted in increased ROS production, which activated the NF-κB pathway leading to expression of inflammatory cytokines. Increased inflammatory cytokine expression resulted in serine phosphorylation of IRS1, which induced insulin resistance (IR). Furthermore these inflammatory cytokines activated the MAPK pathway, which further promoted the serine phosphorylation of IRS1. Insulin resistance resulted in elevated blood glucose. The ER stress inhibitor 4-phenylbutyric acid (4-PBA) inhibited SiO2 NP-induced ROS production. The ROS scavenger N-acetylcysteine (NAC) did not affect SiO2 NP-induced ER stress, but inhibited SiO2 NP-induced activation of the NF-κB and MAPK pathways, expression of inflammatory cytokines, SiO2 NP-induced serine phosphorylation of IRS1, and SiO2 NP-induced elevations of blood glucose. CONCLUSION:Silicon dioxide NPs induced IR through ER stress and generation of ROS, but SiO2 FPs did not. Therefore, lifelong exposure of humans to SiO2 NPs may result in detrimental effects on blood glucose. The results of this study strongly suggested that non-nanoformed SiO2 should be used as food additives.

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Proteinuria and hyperglycemia induce endoplasmic reticulum stress.

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Proteinuria and hyperglycemia induce endoplasmic reticulum stress.

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