Decreased Renal Organic Anion Transporter 3 Expression in Type 1 Diabetic Rats

doi:10.1097/MAJ.0b013e3182831740

The American Journal of the Medical Sciences

Volume 347, Issue 3, March 2014, Pages 221-227

https://doi.org/10.1097/MAJ.0b013e3182831740 Get rights and content

Abstract

Background

Organic anion transporter 3 (Oat3) plays an essential role in the renal excretion of organic anions. Reduced renal Oat3 expression potentially contributes to an impaired anion clearance and causes abnormal kidney function. This study examined the effects of diabetes on the expression and function of rat renal Oat3.

Methods

Experimental diabetes was induced by the administration of streptozotocin. Diabetic rats were randomly assigned to the treatment group or no treatment group with insulin for 4 weeks. The expression of renal Oat3, protein kinase Cα (PKCα), phospho-PKCα and nuclear factor kappa B (NF-κB) p65 were determined by immunoblotting. Estrone sulfate (Es) uptake into renal cortical slices was used as an indicator of renal Oat3 function.

Results

The reduced expression of renal Oat3 was related to the decrease in [³H]Es uptake in a renal cortical slice of the diabetic rat. Insulin treatment restored the impairment of renal Oat3 function and expression. These may be because of the hyperglycemia-induced oxidative stress effectively activating the PKCα and NF-κB. Insulin treatment abolished these processes.

Conclusions

These data are the first to show that the decreased function and expression of renal Oat3 in diabetes was associated with an increase in reactive oxygen species production coinciding with the activation of PKC and NF-κB signaling pathway. These events may affect the transporter protein translocation and/or expression.

Section snippets

Chemicals and Reagents

Human insulin was obtained from Eli Lilly Asia Inc (Bangkok, Thailand). Glucose and triglyceride (TG) assay kits were purchased from Biotech (Bangkok, Thailand). Malondialdehyde (MDA) assay kit was obtained from Cayman Chemical Company (Ann Arbor, MI). Polyclonal antibody against Oat3 was purchased from Cosmo Bio Co., Ltd. (Tokyo, Japan). Antibodies against protein kinase Cα (PKCα) (C-20), phospho-PKCα (Ser657) and nuclear factor (NF)κB p65 (C-20) were obtained from Santa Cruz Biotechnology Co.

Effects of 4-Week Diabetes and Insulin Treatment on Body Weight, Kidney Weight, Kidney Weight to Body Weight Ratio, PG and Serum TG

Four weeks after the diabetic condition was confirmed, the BW significantly decreased in diabetic rats as compared with that of control rats (P < 0.01) (Table 1). In addition, diabetic rats showed renal hypertrophy as indicated by a significant increase in the KW/BW ratio, an index of renal hypertrophy, when compared with control rats (P < 0.01). Insulin treatment for 4 weeks in the diabetes + insulin rats resulted in a marked increase in BW and decreased KW/BW ratio as compared with diabetic

DISCUSSION

The STZ-treated rat is widely used as an animal model of type 1 diabetes. In the present study, the metabolic features of the diabetic condition including the prompt development of profound hyperglycemia, marked increase in serum TG, the weight of kidney and the ratio of KW/BW were observed in diabetic rats. Besides the pathological changes, it was shown that the ES uptake into renal cortical slices, which reflected the function of renal Oat3, was reduced in 4-week STZ-induced diabetic rats.

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Citation Excerpt :
The expression and function of Oats under diabetic conditions have been studied in various animal models. One animal study showed that the activity and protein level of Oat3 were decreased in streptozotocin-induced diabetic rats, which could be restored by insulin treatment (Phatchawan, Chutima, Varanuj, & Anusorn, 2014). In another study using Ins2Akita mouse, a model for diabetes, the mRNA and protein expression levels of Oat1, Oat2, and Oat3 were all reduced (C. Xu et al., 2015).
The members of the organic anion transporter (OAT) family are mainly expressed in kidney, liver, placenta, intestine, and brain. These transporters play important roles in the disposition of clinical drugs, pesticides, signaling molecules, heavy metal conjugates, components of phytomedicines, and toxins, and therefore critical for maintaining systemic homeostasis. Alterations in the expression and function of OATs contribute to the intra- and inter-individual variability of the therapeutic efficacy and the toxicity of many drugs, and to many pathophysiological conditions. Consequently, the activity of these transporters must be highly regulated to carry out their normal functions. This review will present an update on the recent advance in understanding the cellular and molecular mechanisms underlying the regulation of renal OATs, emphasizing on the post-translational modification (PTM), the crosstalk among these PTMs, and the remote sensing and signaling network of OATs. Such knowledge will provide significant insights into the roles of these transporters in health and disease.
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Background
Organic anion transporter 1 (OAT1) plays a vital role in avoiding the potential toxicity of various anionic drugs through the involvement of kidney elimination. We previously demonstrated that ubiquitin conjugation to OAT1 led to OAT1 internalization from cell surface, followed by degradation. Ubiquitination is a dynamic process, where deubiquitination is catalyzed by a class of ubiquitin-specific peptidases.
Methods
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Results
We demonstrated that USP8 overexpression in hOAT1-expressing cells led to an increased hOAT1 transporter activity and expression, which correlated well with a reduced hOAT1 ubiquitination. Such phenomenon was not observed in inactive USP8 mutant-transfected cells. In addition, the knockdown of endogenous USP8 by USP8-specific siRNA resulted in an increased hOAT1 ubiquitination, which correlated well with a decrease in hOAT1 expression and transport activity. Biotinylation experiments demonstrated that USP8-induced increase in hOAT1 expression and transport activity occurred through a deceleration of the rates of hOAT1 internalization and degradation.
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Citation Excerpt :
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This study was supported by the Thailand Research Fund Grant MRG4980200 and the Faculty of Medicine Endowment Fund, Chiang Mai University.

The authors have no financial or other conflicts of interest to disclose.

View full text

Basic InvestigationDecreased Renal Organic Anion Transporter 3 Expression in Type 1 Diabetic Rats

Abstract

Background

Methods

Results

Conclusions

Section snippets

Chemicals and Reagents

Effects of 4-Week Diabetes and Insulin Treatment on Body Weight, Kidney Weight, Kidney Weight to Body Weight Ratio, PG and Serum TG

DISCUSSION

J Pharmacol Sci

J Biol Chem

Kidney Int

Pharmacol Ther

Free Radic Biol Med

J Biol Chem

Life Sci

Kidney Int

Kidney Int

Biochem Pharmacol

Kidney Int

Eur J Pharmacol

Prevalence of diabetes and effect on quality of life in older French living in the community: the PAQUID Epidemiological Survey

J Am Geriatr Soc

Organic anion transporter 3 (Slc22a8) is a dicarboxylate exchanger indirectly coupled to the Na + gradient

Am J Physiol Ren Physiol

Molecular and cellular physiology of renal organic cation and anion transport

Physiol Rev

Gene expression levels and immunolocalization of organic ion transporters in the human kidney

J Am Soc Nephrol

The SLC22 drug transporter family

Pflugers Arch Eur J Physiol

Basic Investigation
Decreased Renal Organic Anion Transporter 3 Expression in Type 1 Diabetic Rats