High glucose induced translocation of Aquaporin8 to chicken hepatocyte plasma membrane: involvement of cAMP, PI3K/Akt, PKC, MAPKs, and microtubule.
Aquaporin8 (AQP8) is a transmembrane water channel that is found mainly in hepatocytes. The direct involvement of AQP8 in high glucose condition has not been established. Therefore, this study examined the effects of high glucose on AQP8 and its related signal pathways in primary cultured chicken hepatocytes. High glucose increased the movement of AQP8 from the intracellular membrane to plasma membrane in a 30 mM glucose concentration and in a time- (> or =10 min) dependent manner. On the other hand, 30 mM mannitol did not affect the translocation of AQP8, which suggested the absence of osmotic effect. Thirty millimolar glucose increased intracellular cyclic adenosine 3, 5-monophosphate (cAMP) level. Moreover, high glucose level induced Akt phosphorylation, protein kinase C (PKC) activation, p44/42 mitogen-activated protein kinases (MAPKs), p38 MAPK, and c-jun NH2-terminal kinase (JNK) phosphorylation. On the other hand, inhibition of each pathway by SQ 22536 (adenylate cyclase inhibitor), LY 294002 (PI3-K phosphatidylinositol 3-kinase inhibitor), Akt inhibitor, staurosporine (PKC inhibitor), PD 98059 (MEK inhibitor), SB 203580 (p38 MAPK inhibitor), or SP 600125 (JNK inhibitor) blocked 30 mM glucose-induced AQP8 translocation, respectively. In addition, inhibition of microtubule movement with nocodazole blocked high glucose-induced AQP8 translocation. High glucose level also increased the level of kinesin light chain and dynein protein expression. In conclusion, high glucose level stimulates AQP8 via cAMP, PI3-K/Akt, PKC, and MAPKs pathways in primary cultured chicken hepatocytes.
Suh
Han Na
HN
Biotherapy Human Resources Center, College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Korea.
Lee
Sang Hun
SH
Lee
Min Young
MY
Heo
Jung Sun
JS
Lee
Yu Jin
YJ
Han
Ho Jae
HJ
D000818:Animals; D020346:Aquaporins / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002645:Chickens; D000242:Cyclic AMP / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology*; D022781:Hepatocytes / Q000187:drug effects / Q000502:physiology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008353:Mannitol / Q000494:pharmacology; D008870:Microtubules / Q000187:drug effects / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D015739:Nocodazole / Q000494:pharmacology; D009995:Osmosis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction
D020346:Aquaporins; D004791:Enzyme Inhibitors; C108330:aquaporin 8; D008353:Mannitol; D000242:Cyclic AMP; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D005947:Glucose; D015739:Nocodazole