C-peptide signals via Gα i to protect against TNF-α-mediated apoptosis of opossum kidney proximal tubular cells

Nawal M. Al-Rasheed, Gary B. Willars, Nigel J. Brunskill

Research output: Contribution to journalArticle

50 Citations (Scopus)

Abstract

Cell loss by apoptosis occurs in renal injury such as diabetic nephropathy. TNF-α is a cytokine that induces apoptosis and has been implicated in the pathogenesis of diabetic nephropathy. The aim was to investigate whether C-peptide or insulin could modulate TNF-α-mediated cell death in opossum kidney proximal tubular cells and to examine the mechanism(s) of any effects observed. C-peptide and insulin protect against TNF-α-induced proximal tubular cell toxicity and apoptosis. Cell viability was analyzed by methylthiazoletetrazolium assay; cell viability was reduced to 60.8 ± 2.7% of control after stimulation with 300 ng/ml TNF-α. Compromised cell viability was reversed by pretreatment with 5 nM C-peptide or 100 nM insulin. TNF-α-induced apoptosis was detected by DNA nick-end labeling and by measuring histone associated DNA fragments using ELISA. By ELISA assay, 300 ng/ml TNF-α increased apoptosis by 145.8 ± 4.9% compared with controls, whereas 5 nM C-peptide and 100 nM insulin reduced apoptosis to 81.6 ± 4.8 and 77.4 ± 3.1% of control, respectively. The protective effects of C-peptide and insulin were associated with activation of NF-êÂ. Activation of NF-κB by C-peptide was pertussis toxin sensitive and dependent on activation of Gα i. Phosphatidylinositol 3-kinase but not extracellular signal regulated mitogen-activated protein kinase mediated C-peptide and insulin activation of NF-κB. The cytoprotective effects of both C-peptide and insulin were related to increased expression of TNF receptor-associated factor 2, the product of an NF-κB-dependent survival gene. These data suggest that C-peptide and/or insulin activation of NF-κB-regulated survival genes protects against TNF-α-induced renal tubular injury in diabetes. The data further support the concept of C-peptide as a peptide hormone in its own right and suggest a potential therapeutic role for C-peptide.

Original languageEnglish
Pages (from-to)986-995
Number of pages10
JournalJournal of the American Society of Nephrology
Volume17
Issue number4
DOIs
Publication statusPublished - 1 Apr 2006

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Opossums
C-Peptide
Apoptosis
Kidney
Insulin
Cell Survival
Diabetic Nephropathies
TNF Receptor-Associated Factor 2
Enzyme-Linked Immunosorbent Assay
Phosphatidylinositol 3-Kinase
Single-Stranded DNA Breaks
Peptide Hormones
Pertussis Toxin
Wounds and Injuries
Mitogen-Activated Protein Kinases
Histones
Protein Kinase C
Genes
Cell Death

Cite this

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title = "C-peptide signals via Gα i to protect against TNF-α-mediated apoptosis of opossum kidney proximal tubular cells",
abstract = "Cell loss by apoptosis occurs in renal injury such as diabetic nephropathy. TNF-α is a cytokine that induces apoptosis and has been implicated in the pathogenesis of diabetic nephropathy. The aim was to investigate whether C-peptide or insulin could modulate TNF-α-mediated cell death in opossum kidney proximal tubular cells and to examine the mechanism(s) of any effects observed. C-peptide and insulin protect against TNF-α-induced proximal tubular cell toxicity and apoptosis. Cell viability was analyzed by methylthiazoletetrazolium assay; cell viability was reduced to 60.8 ± 2.7{\%} of control after stimulation with 300 ng/ml TNF-α. Compromised cell viability was reversed by pretreatment with 5 nM C-peptide or 100 nM insulin. TNF-α-induced apoptosis was detected by DNA nick-end labeling and by measuring histone associated DNA fragments using ELISA. By ELISA assay, 300 ng/ml TNF-α increased apoptosis by 145.8 ± 4.9{\%} compared with controls, whereas 5 nM C-peptide and 100 nM insulin reduced apoptosis to 81.6 ± 4.8 and 77.4 ± 3.1{\%} of control, respectively. The protective effects of C-peptide and insulin were associated with activation of NF-{\^e}{\^A}. Activation of NF-κB by C-peptide was pertussis toxin sensitive and dependent on activation of Gα i. Phosphatidylinositol 3-kinase but not extracellular signal regulated mitogen-activated protein kinase mediated C-peptide and insulin activation of NF-κB. The cytoprotective effects of both C-peptide and insulin were related to increased expression of TNF receptor-associated factor 2, the product of an NF-κB-dependent survival gene. These data suggest that C-peptide and/or insulin activation of NF-κB-regulated survival genes protects against TNF-α-induced renal tubular injury in diabetes. The data further support the concept of C-peptide as a peptide hormone in its own right and suggest a potential therapeutic role for C-peptide.",
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C-peptide signals via Gα i to protect against TNF-α-mediated apoptosis of opossum kidney proximal tubular cells. / Al-Rasheed, Nawal M.; Willars, Gary B.; Brunskill, Nigel J.

In: Journal of the American Society of Nephrology, Vol. 17, No. 4, 01.04.2006, p. 986-995.

Research output: Contribution to journalArticle

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