A higher level of O-glicnacylation of sp1 down regulates gene expression of pi class glutathione s-transferase in diabetic mice.

OLIVERI LEDA; BUZALEH ANA MARIA; MORA SANDRA; ESTHER GEREZ; ZUCCOLI JOHANNA

MAR DEL PLATA

Congreso; LXIII CONGRESO DE SOCIEDAD DE INVESTIGACIÓN CLÍNICA; 2018

SAIC

Diabetes mellitus is characterized by chronic hyperglycemia caused by defects in secretion and/or action of insulin. Hyperglycemia creates free radicals producing oxidative stress, which debilitates the endogenous antioxidant defense system. Glutathione S-transferases (GSTs) are a multigene superfamily of enzymes that catalyze the conjugation of glutathione with electrophilic compounds including those produced during oxidative stress. GSTP, one of the GST isoenzymes, catalyzes conjugation of glutathione with different electrophilic substrates with a particularly high affinity for small unsaturated aldehydes. Little is known about the regulation and expression of GSTP in diabetes. The aim of this study was to evaluate how GSTP is regulated in diabetes. Animals were diabetized with a single dose of streptozotocin. Diabetic animals were treated with vanadate (STZ+V), or insulin (STZ+I) or no treatment (STZ). Total GST activity and expression of GSTP mRNA decrease right after the onset of diabetes and remained low throughout the whole period of the experiment (32 days). Insulin abolished hyperglicemia and restored both GST activity and GSTP mRNA levels. However, vanadate, a well-known insulin mimetic agent, restored the GST activity but only showed a partial effect on hyperglycemia. Since the 5?-regulatory region of mouse GSTP gene contains activator protein-1 (AP1) and SP1 sites involved in transcription activation, we measured both AP1 and Sp1 glycosylation levels in all groups. Both Sp1 and Sp1 O-glycosilated increased in liver of diabetic animals while insulin treatment impaired overexpression and hyperglycosilation maintaining both parameters at the levels of control group. On the other hand, vanadate treatment yielded expression and glycosilation of Sp1 lower than those of control group. JUN protein levels were lower than control in all groups, whereas cFOS protein expression did not differ between treated and control groups. These results suggest that Sp1 hyperglicosilation might be involved in the changes of GSTP expression caused by diabetes