Differential regulation of high glucose-induced glyceraldehyde-3-phosphate dehydrogenase nuclear accumulation in Müller cells by IL-1beta and IL-6.
OBJECTIVE
This study determined the role of the proinflammatory cytokines known to be elevated in the diabetic retina, namely IL-1beta, TNFalpha, and IL-6, in a high glucose-induced nuclear accumulation of GAPDH in retinal Müller cells, an event considered crucial for the induction of cell death.


METHODS
With use of the transformed rat Müller cell line (rMC-1) and isolated human Müller cells (HMCs), the authors examined the effect of high glucose (25 mM), IL-1beta, TNFalpha, IL-6, and high glucose (25 mM) plus inhibitors of the caspase-1/IL-1beta signaling pathway on GAPDH nuclear accumulation, which was evaluated by immunofluorescence analysis.


RESULTS
High glucose induced IL-1beta, weak IL-6, and no TNFalpha production by rMC-1 and HMCs. IL-1beta (1-10 ng/mL) significantly increased GAPDH nuclear accumulation in Müller cells in a concentration-dependent manner within 24 hours. Further, high glucose-induced GAPDH nuclear accumulation in Müller cells was mediated by IL-1beta. Inhibition of the IL-1 receptor using an IL-1 receptor antagonist (IL-1ra; 50 ng/mL) or inhibition of IL-1beta production using a specific caspase-1 inhibitor (YVAD-fmk; 100 microM) significantly decreased high glucose-induced GAPDH nuclear accumulation. In contrast, IL-6 (2 ng/mL) had a strong protective effect attenuating high glucose and IL-1beta-induced GAPDH nuclear accumulation in Müller cells. TNFalpha (1-10 ng/mL) did not have any effect on GAPDH nuclear accumulation.


CONCLUSIONS
These results revealed a novel mechanism for high glucose-induced GAPDH nuclear accumulation in Müller cells through production and autocrine stimulation by IL-1beta. The protective role of IL-6 in high glucose- and IL-1beta-induced toxicity indicates that changes in the balance of these cytokines might contribute to cellular damage mediated by elevated glucose levels.
Yego
E Chepchumba K
EC
Department of Physiology and Biophysics, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106, USA.
Vincent
Jason A
JA
Sarthy
Vijay
V
Busik
Julia V
JV
Mohr
Susanne
S
D000818:Animals; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000201:enzymology*; D002470:Cell Survival; D004305:Dose-Response Relationship, Drug; D019084:Fluorescent Antibody Technique, Indirect; D005947:Glucose / Q000494:pharmacology*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism*; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism* / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism* / Q000494:pharmacology; D009457:Neuroglia / Q000187:drug effects* / Q000201:enzymology; D051381:Rats; D012160:Retina / Q000166:cytology; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000031:analogs & derivatives / Q000494:pharmacology
D053583:Interleukin-1beta; D015850:Interleukin-6; C425776:tyrosyl-valyl-alanyl-aspartic acid fluoromethyl ketone; D014108:Tosylphenylalanyl Chloromethyl Ketone; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D020169:Caspases; D005947:Glucose