Protein kinase C-delta mediates neuronal apoptosis in the retinas of diabetic rats via the Akt signaling pathway.
OBJECTIVE
Protein kinase C (PKC)-delta, an upstream regulator of the Akt survival pathway, contributes to cellular dysfunction in the pathogenesis of diabetes. Herein, we examined the role of PKC-delta in neuronal apoptosis through Akt in the retinas of diabetic rats.


METHODS
We used retinas from 24- and 35-week-old male Otsuka Long-Evans Tokushima fatty (OLETF) diabetic and Long-Evans Tokushima Otsuka (LETO) nondiabetic rats. To assess whether PKC-delta affects Akt signaling and cell death in OLETF rat retinas, we examined 1) PKC-delta activity and apoptosis; 2) protein levels of phosphatidylinositol 3-kinase (PI 3-kinase) p85, heat shock protein 90 (HSP90), and protein phosphatase 2A (PP2A); 3) Akt phosphorylation; and 4) Akt binding to HSP90 or PP2A in LETO and OLETF retinas in the presence or absence of rottlerin, a highly specific PKC-delta inhibitor, or small interfering RNAs (siRNAs) for PKC-delta and HSP90.


RESULTS
In OLETF retinas from 35-week-old rats, ganglion cell death, PKC-delta and PP2A activity, and Akt-PP2A binding were significantly increased and Akt phosphorylation and Akt-HSP90 binding were decreased compared with retinas from 24-week-old OLETF and LETO rats. Rottlerin and PKC-delta siRNA abrogated these effects in OLETF retinas from 35-week-old rats. HSP90 siRNA significantly increased ganglion cell death and Akt-PP2A complexes and markedly decreased HSP90-Akt binding and Akt phosphorylation in LETO retinas from 35-week-old rats compared with those from nontreated LETO rats.


CONCLUSIONS
PKC-delta activation contributes to neuro-retinal apoptosis in diabetic rats by inhibiting Akt-mediated signaling pathways.
Kim
Young-Hee
YH
Department of Anatomy and Neurobiology, School of Medicine, Institute of Health Science, Gyeongsang National University, Jinju, Gyeongnam, South Korea.
Kim
Yoon-Sook
YS
Park
Chang-Hwan
CH
Chung
In-Yong
IY
Yoo
Ji-Myong
JM
Kim
Jae-Geun
JG
Lee
Byung-Ju
BJ
Kang
Sang-Soo
SS
Cho
Gyeong-Jae
GJ
Choi
Wan-Sung
WS
D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001578:Benzopyrans / Q000494:pharmacology; D001835:Body Weight / Q000187:drug effects; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism / Q000503:physiopathology*; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D020287:In Situ Nick-End Labeling; D008297:Male; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010424:Pentobarbital / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011430:Propoxycaine / Q000494:pharmacology; D011485:Protein Binding; D051745:Protein Kinase C-delta / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D020334:Rats, Inbred OLETF; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D000098:Acetophenones; D001578:Benzopyrans; D018841:HSP90 Heat-Shock Proteins; D034741:RNA, Small Interfering; C005717:proxymetacaine; C085746:rottlerin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D051745:Protein Kinase C-delta; D054648:Protein Phosphatase 2; D011430:Propoxycaine; D010424:Pentobarbital