Identification of a novel stress activated kinase in kidney and heart

Resveratrol reverses ET-1-evoked mitogenic effects in human coronary arterial cells by activating the kinase-G to inhibit ERK-enzymes

In human coronary smooth muscle cells (HCSMC), treatment with the vascular mitogen; endothelin-1 (ET-1), induced cell proliferation and stimulated ERK-1/2 phosphorylation at active sites. Pretreatment with the MEK-ERK inhibitor (PD98059) appreciably reversed the mitogenic effects of ET-1. On the other hand, pretreatment with the polyphenolic stilbene resveratrol (RSVL, 1-100 microM) triggered more prominent inhibition of ET-1-evoked cell proliferation and ERK1/2 activation. Besides, RSVL also markedly (2-3 fold) and rapidly enhanced cGMP formation, but had no effect on cAMP levels. This RSVL-evoked upregulation of cGMP was insensitive to pretreatment with the soluble guanylyl cyclase (sGC)-inhibitor (ODQ, 10 microM), but was ablated with an inhibitor of pGC (PMA, 0.1 microM). Further, pretreatment with the specific cGMP-phosphodiesterase inhibitor, zaprinast (10 microM) appreciably augmented RSVL-evoked cGMP formation, ERK inhibition, and cytostatic response. Moreover, the RSVL-induced ERK-inhibitory effects were significantly reversed by the kinase-G inhibitor, KT-5823 (10 microM; 69%), but not by the kinase-A inhibitor (KT-5720). These results demonstrate a novel signaling pathway for RSVL that leads from activation of the pGC/kinase-G system to inhibition of ERK1/2 and their downstream nuclear targets. This pathway functions to counteract the atherogenic signaling induced by vascular mitogens.

Poly(ADP-ribose) polymerase-mediated cell injury in acute renal failure

Acute Renal Failure (ARF) is the most costly kidney disease in hospitalized patients and remains as a serious problem in clinical medicine. The mortality rate among ARF patients remains around 50% and no pharmaceutical agents are currently available to improve its clinical outcome. Although several successful therapeutic approaches have been developed in animal models of the disease, translation of the results to clinical ARF remains elusive. Understanding the cellular and molecular mechanisms of vascular and tubular dysfunction in ARF is important for developing acceptable therapeutic interventions. Following an ischemic episode, cells of the affected nephron undergo necrotic and/or apoptotic cell death. Necrotic cell death is widely considered to be a futile process that cannot be modulated by pharmacological means as opposed to apoptosis. However, recent reports from various laboratories including ours indicate that inhibition or absence of poly(ADP)-ribose polymerase (PARP), one of the molecules involved in cell death, provides remarkable protection in disease models such as stroke, myocardial infarction and renal ischemia which are characterized predominantly by necrotic type of cell death. Overactivation of PARP in conditions such as ischemic renal injury leads to cellular depletion of its substrate NAD+ and consequently ATP. The severely compromised cellular energetic state induces acute cell injury and diminishes renal functions. PARP activation also enhances the expression of proinflammatory agents and adhesion molecules in ischemic kidneys. Pharmacological inhibition and gene ablation of PARP-1 decreased energy depletion, inflammatory response and improved renal functions in the setting renal ischemia/reperfusion injury. The biochemical pathways and the cellular and molecular mechanisms mediated by PARP-1 activation in eliciting the energy depletion and inflammatory responses in ischemic kidney are not fully elucidated. Dissecting the molecular mechanisms by which PARP activation contributes to oxidant-induced cell death will provide new strategies to interfere in those pathways to modulate cell death in renal ischemia. The current review evaluates the experimental evidences in animal and cell culture models implicating PARP as a pathophysiological modulator of acute renal failure with particular emphasis on ischemic renal injury.

Inhibition of p38 mitogen-activated protein kinase may decrease intestinal epithelial cell apoptosis and improve intestinal epithelial barrier function after ischemia- reperfusion injury

AIM: To investigate the role of p38 mitogen-activated protein kinase in rat small intestine after ischemia-reperfusion (I/R) insult and the relationship between activation of p38 MAPK and apoptotic cell death of intestine.

METHODS: Ninety Wistar rats were divided randomly into three groups, namely sham-operated group (C), I/R vehicle group (R) and SB203580 pre-treated group (S). In groups R and S, the superior mesenteric artery (SMA) was separated and occluded for 45 min, then released for reperfusion for 0.25, 0.5, 1, 2, 6, 12 and 24 h. In group C, SMA was separated without occlusion. Plasma D-lactate levels were examined and histological changes were observed under a light microscope. The activity of p38 MAPK was determined by Western immunoblotting and apoptotic cells were detected by the terminal deoxynucleotidyl transferase (TdT)-mediated dUDP-biotin nick end labeling (TUNEL).

RESULTS: Intestinal ischemia followed by reperfusion activated p38 MAPK, and the maximal level of activation (7.3-fold vs sham-operated group) was reached 30 min after I/R. Treatment with SB 203580, a p38 MAPK inhibitor, reduced intestinal apoptosis (26.72±3.39% vs 62.50±3.08% in I/R vehicle, P<0.01) and decreased plasma D-lactate level (0.78±0.15 mmol/L in I/R vehicle vs 0.42±0.17 mmol/L in SB-treated group) and improved post-ischemic intestinal histological damage.

CONCLUSION: p38 MAPK plays a crucial role in the signal transduction pathway mediating post-ischemic intestinal apoptosis, and inhibition of p38 MAPK may attenuate ischemia-reperfusion injury.

P38 mitogen-activated protein kinase inhibition attenuates ischemia-reperfusion injury of the rat liver

BACKGROUND

Several studies have implicated the mitogen-activated protein kinase (MAPK) signal pathway in non-hepatic organ ischemia-reperfusion injury. However, the role of p38 MAPK in hepatic ischemia-reperfusion injury remains unclear. This study investigated the role of p38 MAPK in hepatic ischemia-reperfusion injury.

METHODS

Male Sprague-Dawley rats were divided into 4 groups (sham, FR-only, control, and FR-treated groups). The animals in the control and FR-treated groups were subjected to 30 minutes of warm ischemia with congestion of the gut. The FR-only and FR-treated groups received FR167653 (FR), which is a novel p38 MAPK inhibitor. The serum levels of aspartate transaminase, alanine transaminase, lactate dehydrogenase, tumor necrosis factor-alpha (TNF-alpha), and interleukin-1beta (IL-1beta) were measured (each, n = 6). Liver tissue blood flow was measured at pre-ischemia, end-ischemia, and 30, 60, 90, and 120 minutes after reperfusion (each, n = 4). The liver tissues in the control and FR-treated groups were excised for p38 MAPK and c-Jun N-terminal kinase (JNK) analyses and histopathology (each, n = 4).

RESULTS

Serum levels of aspartate transaminase, alanine transaminase, lactate dehydrogenase, TNF-alpha, and IL-1beta were significantly lower in the FR-treated group than in the control group, and liver tissue blood flow was significantly higher in the FR-treated group than in the control group. Histopathologically, tissue damage was milder in the FR-treated group than in the control group. Both p38 MAPK and JNK were markedly phosphorylated after 30 minutes of reperfusion, and FR inhibited the phosphorylation of p38 MAPK without affecting the JNK.

CONCLUSIONS

FR decreased serum TNF-alpha and IL-1beta levels and liver injury associated with the inhibition of p38 MAPK activation. These results suggest that inhibiting the activation of p38 MAPK may attenuate warm ischemia-reperfusion injury of the liver.

MAPK signaling and the kidney

Following an overview of the biochemistry of mitogen-activated protein kinase (MAPK) pathways, the relevance of these signaling events to specific models of renal cell function and pathophysiology, both in vitro and in vivo, will be emphasized. In in vitro model systems, events activating the principal MAPK families [extracellular signal-regulated and c-Jun NH(2)-terminal kinase and p38] have been best characterized in mesangial and tubular epithelial cell culture systems and include peptide mitogens, cytokines, lipid mediators, and physical stressors. Several in vivo models of proliferative or toxic renal injury are also associated with aberrant MAPK regulation. It is anticipated that elucidation of downstream effector signaling mechanisms and a clearer understanding of the immediate and remote upstream activating pathways, when applied to these highly clinically relevant model systems, will ultimately provide much greater insight into the basis for specificity now seemingly absent from these signaling events.

Characterization of a novel human serine protease that has extensive homology to bacterial heat shock endoprotease HtrA and is regulated by kidney ischemia

We report the isolation and characterization of a cDNA encoding the novel mammalian serine protease Omi. Omi protein consists of 458 amino acids and has homology to bacterial HtrA endoprotease, which acts as a chaperone at low temperatures and as a proteolytic enzyme that removes denatured or damaged substrates at elevated temperatures. The carboxyl terminus of Omi has extensive homology to a mammalian protein called L56 (human HtrA), but unlike L56, which is secreted, Omi is localized in the endoplasmic reticulum. Omi has several novel putative protein-protein interaction motifs, as well as a PDZ domain and a Src homology 3-binding domain. Omi mRNA is expressed ubiquitously, and the gene is localized on human chromosome 2p12. Omi interacts with Mxi2, an alternatively spliced form of the p38 stress-activated kinase. Omi protein, when made in a heterologous system, shows proteolytic activity against a nonspecific substrate beta-casein. The proteolytic activity of Omi is markedly up-regulated in the mouse kidney following ischemia/reperfusion.

Resveratrol inhibits MAPK activity and nuclear translocation in coronary artery smooth muscle: reversal of endothelin-1 stimulatory effects

In porcine coronary arteries, short-term treatment with resveratrol (RSVL) substantially inhibited MAPK activity (IC50 = 37 microM); and immunoblot analyses revealed consistent reduction in the phosphorylation of ERK-1/-2, JNK-1 and p38, at active sites. Endothelin-1 (ET-1), a primary antecedent in coronary heart diseases, enhanced MAPK activity, phosphorylation and nuclear translocation in a concentration-responsive but RSVL-sensitive manner. RSVL had no effect on basal or forskolin-stimulated cAMP levels, a known downregulator of the MAPK cascade. Likewise, inhibition of MAPK by RSVL was not reversed by the estrogen receptor blockers tamoxifen and ICI-182,780. Conversely, RSVL remarkably attenuated basal and ET-1-evoked protein tyrosine phosphorylation. Because MAPKs promote smooth muscle proliferation and contraction, their current inhibition may contribute to the putative protection by RSVL against coronary heart diseases. These effects apparently do not involve interaction with estrogen receptors.