Jonas, Jean-Christophe
[UCL]
Guiot, Yves
[UCL]
Rahier, Jacques
[UCL]
Henquin, Jean-Claude
[UCL]
AIM/HYPOTHESIS: Increased expression of haeme-oxygenase 1 (HO1) and other antioxidant enzymes could improve pancreatic beta-cell survival under stressful conditions, including hyperglycaemia. However, how hyperglycaemia increases islet HO1 expression is not known. METHODS: Rat islets were pre-cultured for 1 week in RPMI medium containing 10 mmol x l(-1) glucose (G10), and further cultured overnight in G5-G30 plus various test substances. Islet HO1 mRNA and protein expression was measured by semiquantitative RT-PCR, western blot, and immunohistochemistry. RESULTS: Islet HO1 mRNA expression was minimal after overnight culture in G10, slightly increased in G5, and increased by five- to ten-fold in G30 in parallel with a heterogeneous increase in beta-cell HO1 protein expression. The effect of G30 was fully inhibited by agents decreasing cytosolic Ca2+ (diazoxide, nimodipine), but was only slightly reproduced by agents raising Ca2+ (tolbutamide, 30 mmol x l(-1) potassium). It was also suppressed by the alpha2-adrenoceptor agonist clonidine, whereas dibutyryl-cyclic-AMP largely increased beta-cell HO1 expression. The induction of HO1 mRNA expression by G30 was independent from changes in medium insulin concentration, but was completely inhibited by a cocktail of antioxidants. In contrast to HO1, islet mRNA expression of glutathione peroxidase and constitutive haeme-oxygenase 2 were not affected by G30, nor by dibutyryl-cyclic-AMP. CONCLUSION/INTERPRETATION: High glucose and dibutyryl-cyclic-AMP stimulate expression of HO1 in rat pancreatic beta cells. The inhibition of HO1 expression in G30 by nimodipine, clonidine, and antioxidants, suggests that Ca2+ influx and cyclic-AMP are necessary for the generation of oxidative stress by G30, or for the stimulation of beta-cell HO1 expression by increased oxidative stress.
Bibliographic reference |
Jonas, Jean-Christophe ; Guiot, Yves ; Rahier, Jacques ; Henquin, Jean-Claude. Haeme-oxygenase 1 expression in rat pancreatic beta cells is stimulated by supraphysiological glucose concentrations and by cyclic AMP.. In: Diabetologia : clinical and experimental diabetes and metabolism, Vol. 46, no. 9, p. 1234-1244 (2003) |
Permanent URL |
http://hdl.handle.net/2078.1/12865 |