Ischemic preconditioning attenuates postischemic leukocyte--endothelial cell interactions: role of nitric oxide and protein kinase C.
BACKGROUND
Ischemic preconditioning (IPC) produces immediate tolerance to subsequent prolonged ischemia/reperfusion (I/R), although the underlying mechanism remains unknown. The purpose of this study was to examine the role of nitric oxide (NO) and protein kinase C (PKC) in IPC-attenuated post ischemic leukocyte-endothelium interactions.


RESULTS
Male Sprague-Dawley rats were randomized (n=8 per group) into 5 groups: sham-operated control group, IPC group, I/R group (4 h of pubic epigastric artery ischemia followed by 2 h of reperfusion), IPC+I/R group (30 min of ischemia followed by 30 min of reperfusion before I/R), and chelerythrine (PKC inhibitor)+IPC+I/R group. Intravital microscopy was used to observe leukocyte-endothelium interaction and to quantify functional capillaries in rat cremaster muscle flaps. The mRNA expressions of neuronal (n) NO synthase (NOS), inducible (i) NOS, and endothelial (e) NOS were determined by reverse transcription-polymerase chain reaction. The results showed that besides increasing functional capillary density, IPC also prevents I/R-induced increases in leukocyte rolling, adhesion, and migration. In the chelerythrine+IPC+I/R group, the IPC protective action was inhibited by the addition of chelerythrine. It was also observed that IPC upregulated nNOS, iNOS, and eNOS mRNA in I/R injured tissue, but this effect was not blocked by chelerythrine. Furthermore, specifically pretreated nNOS and iNOS inhibitors, along with a nonselective NOS inhibitor, were used in the IPC+I/R group to examine their possible antagonistic effects on leukocyte-endothelium interactions. Inhibition of the nNOS and iNOS activities did not block the beneficial effects of IPC. In contrast, pretreatment with the nonselective NOS inhibitor (NG-nitro-L-arginine methylester) in the IPC+I/R group almost completely blocked the protective effect of IPC.


CONCLUSIONS
Both NOS and PKC play a protective role during IPC, but probably in distinct ways. Furthermore, the results also indicate that eNOS, but not nNOS nor iNOS, is the key mediator of IPC-attenuated I/R-induced microcirculatory disturbance.
Huang
Shiang-Suo
SS
Department of Pharmacology and Institute of Medicine, College of Medicine, Chung Shan Medical University, Taichung, and Chang Gung Memorial Hospital, Tao-Yuan, Taiwan.
Wei
Fu-Chan
FC
Hung
Li-Man
LM
D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D042783:Endothelial Cells / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D019194:Ischemic Preconditioning; D007962:Leukocytes / Q000187:drug effects / Q000502:physiology*; D008833:Microcirculation / Q000502:physiology; D018482:Muscle, Skeletal / Q000201:enzymology; D009569:Nitric Oxide / Q000502:physiology*; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology; D015854:Up-Regulation
D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D011493:Protein Kinase C