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Exendin-4 inhibits interleukin-1beta-induced iNOS expression at the protein level, but not at the transcriptional and posttranscriptional levels, in RINm5F beta-cells.
J Endocrinol 2009; 202(1):65-75JE

Abstract

Cytokines such as interleukin-1beta (IL-1beta) stimulate inducible nitric oxide synthase (iNOS) expression and nitric oxide overproduction leading to beta-cell damage. Meanwhile, glucagon-like peptide-1 (GLP-1) and its potent analog exendin-4 (EX-4) were well known for beta-cell proliferation. However, the protective mechanisms of GLP-1 in beta-cells exposed to cytokines were not fully elucidated. Therefore, the effects of EX-4 on the IL-1beta-induced iNOS gene expression were investigated employing RINm5F beta-cells. EX-4 inhibited IL-1beta-induced iNOS protein expression and nitrite production. However, northern blot and promoter analyses showed that EX-4 failed to inhibit IL-1beta-induced iNOS mRNA expression and iNOS promoter activity. By electrophoretic mobility shift assay (EMSA), EX-4 did not alter the binding activity of NF-kappaB to the iNOS promoter. Consistent with the EMSA result, EX-4 did not inhibit nuclear translocation of p65. We also tested the effect of EX-4 on iNOS mRNA stability. Actinomycin D chase experiments showed that EX-4 did not affect the decay rate of iNOS mRNA and the promoter assay using the construct containing 3'-untranslated region of iNOS showed that EX-4 did not alter the stability of iNOS mRNA. Meanwhile, forskolin significantly inhibited IL-1beta-induced iNOS protein, which was reversed by H-89, a protein kinase A (PKA) inhibitor. Moreover, EX-4 pretreatment restored IL-1beta-induced decrease in cAMP toward control level. Additionally, the cycloheximide chase study demonstrated that EX-4 significantly accelerated iNOS protein degradation. We therefore concluded that EX-4 inhibited IL-1beta-induced iNOS protein and nitrite production via cAMP/PKA system irrespective of both transcriptional and posttranscriptional mechanisms of iNOS gene, and this inhibitory effect of EX-4 appears to be regulated at posttranslational level.

Authors+Show Affiliations

Departments of Physiology, College of Medicine, The Catholic University of Korea, Seoul, South Korea.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

19398497

Citation

Kang, Jung-Hoon, et al. "Exendin-4 Inhibits Interleukin-1beta-induced iNOS Expression at the Protein Level, but Not at the Transcriptional and Posttranscriptional Levels, in RINm5F Beta-cells." The Journal of Endocrinology, vol. 202, no. 1, 2009, pp. 65-75.
Kang JH, Chang SY, Jang HJ, et al. Exendin-4 inhibits interleukin-1beta-induced iNOS expression at the protein level, but not at the transcriptional and posttranscriptional levels, in RINm5F beta-cells. J Endocrinol. 2009;202(1):65-75.
Kang, J. H., Chang, S. Y., Jang, H. J., Kim, D. B., Ryu, G. R., Ko, S. H., ... Kim, M. J. (2009). Exendin-4 inhibits interleukin-1beta-induced iNOS expression at the protein level, but not at the transcriptional and posttranscriptional levels, in RINm5F beta-cells. The Journal of Endocrinology, 202(1), pp. 65-75. doi:10.1677/JOE-08-0507.
Kang JH, et al. Exendin-4 Inhibits Interleukin-1beta-induced iNOS Expression at the Protein Level, but Not at the Transcriptional and Posttranscriptional Levels, in RINm5F Beta-cells. J Endocrinol. 2009;202(1):65-75. PubMed PMID: 19398497.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Exendin-4 inhibits interleukin-1beta-induced iNOS expression at the protein level, but not at the transcriptional and posttranscriptional levels, in RINm5F beta-cells. AU - Kang,Jung-Hoon, AU - Chang,Seo-Yoon, AU - Jang,Hyun-Jong, AU - Kim,Dong-Bin, AU - Ryu,Gyeong Ryul, AU - Ko,Seung Hyun, AU - Jeong,In-Kyung, AU - Jo,Yang-Hyeok, AU - Kim,Myung-Jun, Y1 - 2009/04/27/ PY - 2009/4/29/entrez PY - 2009/4/29/pubmed PY - 2009/7/23/medline SP - 65 EP - 75 JF - The Journal of endocrinology JO - J. Endocrinol. VL - 202 IS - 1 N2 - Cytokines such as interleukin-1beta (IL-1beta) stimulate inducible nitric oxide synthase (iNOS) expression and nitric oxide overproduction leading to beta-cell damage. Meanwhile, glucagon-like peptide-1 (GLP-1) and its potent analog exendin-4 (EX-4) were well known for beta-cell proliferation. However, the protective mechanisms of GLP-1 in beta-cells exposed to cytokines were not fully elucidated. Therefore, the effects of EX-4 on the IL-1beta-induced iNOS gene expression were investigated employing RINm5F beta-cells. EX-4 inhibited IL-1beta-induced iNOS protein expression and nitrite production. However, northern blot and promoter analyses showed that EX-4 failed to inhibit IL-1beta-induced iNOS mRNA expression and iNOS promoter activity. By electrophoretic mobility shift assay (EMSA), EX-4 did not alter the binding activity of NF-kappaB to the iNOS promoter. Consistent with the EMSA result, EX-4 did not inhibit nuclear translocation of p65. We also tested the effect of EX-4 on iNOS mRNA stability. Actinomycin D chase experiments showed that EX-4 did not affect the decay rate of iNOS mRNA and the promoter assay using the construct containing 3'-untranslated region of iNOS showed that EX-4 did not alter the stability of iNOS mRNA. Meanwhile, forskolin significantly inhibited IL-1beta-induced iNOS protein, which was reversed by H-89, a protein kinase A (PKA) inhibitor. Moreover, EX-4 pretreatment restored IL-1beta-induced decrease in cAMP toward control level. Additionally, the cycloheximide chase study demonstrated that EX-4 significantly accelerated iNOS protein degradation. We therefore concluded that EX-4 inhibited IL-1beta-induced iNOS protein and nitrite production via cAMP/PKA system irrespective of both transcriptional and posttranscriptional mechanisms of iNOS gene, and this inhibitory effect of EX-4 appears to be regulated at posttranslational level. SN - 1479-6805 UR - https://www.unboundmedicine.com/medline/citation/19398497/Exendin_4_inhibits_interleukin_1beta_induced_iNOS_expression_at_the_protein_level_but_not_at_the_transcriptional_and_posttranscriptional_levels_in_RINm5F_beta_cells_ L2 - https://joe.bioscientifica.com/doi/10.1677/JOE-08-0507 DB - PRIME DP - Unbound Medicine ER -