Regulation of protein kinases and coregulatory interplay of S-100beta and serotonin transporter on serotonin levels in diabetic rat brain.

Protein kinases are critical component in the regulation of signal transduction pathways, including neurotransmitters. Our previous studies have shown that serotonin (5-HT) altered under diabetic condition was accompanied by alterations of protein kinase C-alpha (PKC-alpha) and CaMKII, and those alterations were reversed after insulin administration. The current study showed that alloxan-induced diabetic animals revealed hyperglycemia and was associated with an increase in the content of 5-HT, PKC-alpha expression and PKC activity (P < 0.05) simultaneously in striatum (ST), midbrain (MB), pons medulla (PM), cerebellum (CB), and cerebral cortex (CCX) from 7 days to 60 days. Although the 5-HT levels in hippocampus (HC) and hypothalamus (HT) were not altered, the PKC-alpha expression and PKC activity showed increases (P < 0.05) in level in HC. Insulin administration reversed all these changes to a normal level. In contrast, the in vitro study has shown that the 5-HT levels correlated with PKC-alpha expressions as well as PKC activity (P < 0.05) only in ST, MB, and CB either after induction with phorbol 12-myristate 13-acetate (PMA) or blocking with chelerythrine, whereas PM and CCX remained elevated (P < 0.05), implying a regulatory role for PKC-alpha only in ST, MB, and CB. However, our consecutive studies have shown that the 5-HT level in PM was regulated by p38-mitogen-activated protein kinase (p38-MAPK) both in vivo and in vitro, whereas the 5-HT level in CCX was coregulated by S-100beta by protein-protein interaction with serotonin transporter (SERT) via 8-bromoadenosine 3',5'-cyclic monophosphate sodium salt (8-Br-cAMP)-induced cAMP/PKAII pathway(s). 2008 Wiley-Liss, Inc.