Cellular ischemia results in activation of a number of kinases, including p38 mitogen-activated protein kinase (MAPK); however, it is not yet clear whether p38 MAPK activation plays a role in cellular damage or is part of a protective response against ischemia. We have developed a model to study ischemia in cultured neonatal rat cardiac myocytes. In this model, two distinct phases of p38 MAPK activation were observed during ischemia. The first phase began within 10 min and lasted less than 1 h, and the second began after 2 h and lasted throughout the ischemic period. Similar to previous studies using in vivo models, the nonspecific activator of p38 MAPK and c-Jun NH 2 -terminal kinase, anisomycin, protected cardiac myocytes from ischemic injury, decreasing the release of cytosolic lactate dehydrogenase by approximately 25%. We demonstrated, however, that a selective inhibitor of p38 MAPK, SB 203580, also protected cardiac myocytes against extended ischemia in a dose-dependent manner. The protective effect was seen even when the inhibitor was present during only the second, sustained phase of p38 MAPK activation. We found that ischemia induced apoptosis in neonatal rat cardiac myocytes and that SB 203580 reduced activation of caspase-3, a key event in apoptosis. These results suggest that p38 MAPK induces apoptosis during ischemia in cardiac myocytes and that selective inhibition of p38 MAPK could be developed as a potential therapy for ischemic heart disease.The heart is subjected to episodes of ischemia followed by reperfusion in a number of situations, including angina, myocardial infarction, and cardiac surgery, and these stresses can result in cell injury and death. Part of the cellular response to ischemia/reperfusion is activation of several members of the mitogen-activated protein kinase (MAPK) 1 family. In many different cell types, p38 MAPK and c-Jun NH 2 -terminal kinase (JNK) family members are activated predominantly by cellular stresses or inflammatory signals, e.g. hyperosmolarity, chemical or heat stress, endotoxin, and cytokines (1-4), whereas the extracellular signal-regulated kinases (ERKs) are activated by mitogenic stimuli (5).In the isolated perfused rat heart, p38 MAPK is activated by global ischemia, and activation is maintained during reperfusion (6, 7). In the same model, neither ERKs nor JNKs are activated by ischemia, whereas reperfusion after ischemia activates JNK (6 -8). Different studies have shown activation (8) or lack of activation (6) of ERKs on reperfusion, possibly the result of different assay methods. More recently, it was observed that although JNK1 (also termed JNK46) is not activated by ischemia, this stress results in translocation of JNK1 to the nucleus, where it is then phosphorylated and activated on reperfusion (9). Ischemia and reperfusion also activate members of the MAPK family in kidney and liver differentially (7, 10, 11). However it is not clear from these studies whether activation of these kinases is part of the protective response of the cell or if these si...

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Pancreatic secretion is required for efficient cholesterol absorption by the intestine, but the factors responsible for this effect have not been clearly defined. To identify factors involved and to investigate their role in cholesterol uptake, we studied the effect of Viokase ® , a porcine pancreatic extract, on cholesterol uptake into human intestinal Caco-2 cells. Viokase is capable of facilitating cholesterol uptake into these cells such that the level of uptake is 5-fold higher in the presence of solubilized Viokase. This stimulation is time-dependent and is dependent on the presence of bile salt. However, bile salt-stimulated pancreatic cholesterol esterase, which has been proposed to mediate cholesterol uptake, is not fully responsible. The major cholesterol transport activity was purified and identified as pancreatic phospholipase A 2 . Anti-phospholipase A 2 antibodies abolished virtually all of the phospholipase A 2 and cholesterol transport activity of solubilized Viokase. We demonstrate that both phospholipase A 2 and cholesterol esterase increase cholesterol uptake by hydrolyzing the phosphatidylcholine that is used to prepare the cholesterol-containing micelles. In the absence of cholesterol esterase or phospholipase A 2 , uptake of cholesterol from micelles containing phosphatidylcholine is not as efficient as uptake from micelles containing phospholipase A 2 -hydrolytic products. These results indicate that phospholipase A 2 may mediate cholesterol absorption by altering the physical-chemical state of cholesterol within the intestine.

These results demonstrate that arachidonic acid selectively activates delta and epsilonPKC in neonatal rat cardiac myocytes, leading to protection from ischaemia. We suggest this is a potential mechanism of PKC activation during PC. In addition, our results suggest that different classes of free fatty acid directly exert cardioprotection from ischaemic injury in cardiac myocytes.

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