Distinct and sequential upregulation of genes regulating cell growth and cell cycle progression during hepatic ischemia-reperfusion injury

Abstract

Ischemia-reperfusion injury (IRI) in liver and other organs is manifested as an injury phase followed by recovery and resolution. Control of cell growth and proliferation is essential for recovery from the injury. We examined the expression of three related regulators of cell cycle progression in liver IRI: spermidine/spermine N-acetyltransferase (SSAT), p21 (a cyclin-dependent kinase inhibitor), and stathmin. Mice were subjected to hepatic IRI, and liver tissues were harvested at timed intervals. The expression of SSAT, the rate-limiting enzyme in the polyamine catabolic pathway, had increased fivefold 6 h after IRI and correlated with increased putrescine levels in the liver, consistent with increased SSAT enzymatic activity in IRI. The expression of p21, which is transactivated by p53, was undetectable in sham-operated animals but was heavily induced at 12 and 24 h of reperfusion and declined to undetectable baseline levels at 72 h of reperfusion. The interaction of the polyamine pathway with the p53-p21 pathway was shown in vitro, where activation of SSAT with polyamine analog or the addition of putrescine to cultured hepatocytes induced the expression of p53 and p21 and decreased cell viability. The expression of stathmin, which is under negative transcriptional regulation by p21 and controls cell proliferation and progression through mitosis, remained undetectable at 6, 12, and 24 h of reperfusion and was progressively and heavily induced at 48 and 72 h of reperfusion. Double-immunofluorescence labeling with antibodies against stathmin and PCNA, a marker of cell proliferation, demonstrated colocalization of stathmin and PCNA at 48 and 72 h of reperfusion in hepatocytes, indicating the initiation of cell proliferation. The distinct and sequential upregulation of SSAT, p21, and stathmin, along with biochemical activation of the polyamine catabolic pathway in IRI in vivo and the demonstration of p53-p21 upregulation by SSAT and putrescine in vitro, points to the important role of regulators of cell growth and cell cycle progression in the pathophysiology and/or recovery in liver IRI. The data further suggest that SSAT may play a role in the initiation of injury, whereas p21 and stathmin may be involved in the resolution and recovery after liver IRI.

Distinct contributions of CD4+T cell subsets in hepatic ischemia/reperfusion injury

“…We have previously shown that after hepatic I/R, signals for liver recovery/regeneration do not occur until after 24 h of reperfusion (3,22). Accordingly, although no differences were seen in the degree of liver injury as manifested by serum ALT levels and histology after 8 h of reperfusion in this study, TCR-␦ deficiency may have effects on liver recovery and regeneration.…”

Overexpression of far upstream element binding proteins: A mechanism regulating proliferation and migration in liver cancer cells

“…21,22 The microtubule-destabilizing protein stathmin is indeed expressed only in small quantities by resting hepatocytes but is highly expressed by mitotic hepatocytes during regeneration after hepatic ischemia/reperfusion and partial hepatectomy and in hepatocarcinogenesis. 4,23 Therefore, stathmin fulfills all the requirements of a protein whose expression is temporarily induced in hepatocytes of normal liver tissue after stimulation of cell growth but is reduced to a basal level after cessation of stimuli. Although a fast effect on stathmin expression was observed after FBP-1 inhibition (⌬6 hours), no previously described FUSE site was found upstream of the first STMN1 exon (up to Ϫ2,000 bp).…”

Hepatocyte-specific ablation of spermine/spermidine-N1-acetyltransferase gene reduces the severity of CCl4-induced acute liver injury

“…A P value of Ͻ 0.05 was considered statistically significant. 4 -treated mice. The hepatic expression of SSAT, SMO, and ODC transcripts is induced as early as 6 h post-CCl 4 administration (Fig.…”

“…Although SSAT expression increases in CCl 4 -induced liver injury its role and the contribution of enhanced polyamine catabolism to the pathophysiology of hepatotoxic injuries in general, and CCl 4 -induced liver injury in particular, are not understood (21). Recent studies indicate that ␣-methylspermidine, a stable polyamine mimetic, has an ameliorative effect on CCl 4 -induced liver toxicity, suggesting that polyamines and their catabolism are important mediators of this injury (13). We hypothesize that increased SSAT expression and activity in the hepatocytes of animals treated with CCl 4 contributes to liver injury.…”

“…1). The expression and activity of SSAT increases in organs (e.g., liver, kidney, and brain) subjected to ischemia-reperfusion and septic and traumatic injuries (4,35,37,39). The ablation of the SSAT gene reduces the severity of renal and hepatic ischemia-reperfusion and endotoxin-induced renal injuries (35,37).…”