GGsTop, a novel and specific γ-glutamyl transpeptidase inhibitor, protects hepatic ischemia-reperfusion injury in rats

Abstract

Ischemia-reperfusion (IR) injury is a major clinical problem and is associated with numerous adverse effects. GGsTop [2-amino-4{[3-(carboxymethyl)phenyl](methyl)phosphono}butanoic acid] is a highly specific and irreversible γ-glutamyl transpeptidase (γ-GT) inhibitor. We studied the protective effects of GGsTop on IR-induced hepatic injury in rats. Ischemia was induced by clamping the portal vein and hepatic artery of left lateral and median lobes of the liver. Before clamping, saline (IR group) or saline containing 1 mg/kg body wt of GGsTop (IR-GGsTop group) was injected into the liver through the inferior vena cava. At 90 min of ischemia, blood flow was restored. Blood was collected before induction of ischemia and prior to restoration of blood flow and at 12, 24, and 48 h after reperfusion. All the animals were euthanized at 48 h after reperfusion and the livers were harvested. Serum levels of alanine transaminase, aspartate transaminase, and γ-GT were significantly lower after reperfusion in the IR-GGsTop group compared with the IR group. Massive hepatic necrosis was present in the IR group, while only few necroses were present in the IR-GGsTop group. Treatment with GGsTop increased hepatic GSH content, which was significantly reduced in the IR group. Furthermore, GGsTop prevented increase of hepatic γ-GT, malondialdehyde, 4-hydroxynonenal, and TNF-α while all these molecules significantly increased in the IR group. In conclusion, treatment with GGsTop increased glutathione levels and prevented formation of free radicals in the hepatic tissue that led to decreased IR-induced liver injury. GGsTop could be used as a pharmacological agent to prevent IR-induced liver injury and the related adverse events.

Inhibition of γ‐glutamyltransferase ameliorates ischaemia‐reoxygenation tissue damage in rats with hepatic steatosis

“…In the current study, arrest of γ‐GT activity employing GGsTop resulted in retaining normal GSH levels and prevented increase of hepatic MDA levels. This observation is in par with our previous report of maintaining normal hepatic GSH levels and blocking MDA formation during GGsTop treatment (Tamura et al, 2016).…”

“…In the current study, we also noticed a significant increase of hepatic γ‐GT activity after IR‐injury. Hepatic Kupffer cells are activated during IR‐injury resulting in increased production of several pro‐inflammatory cytokines, especially TNF‐α (Hirakawa et al, 2019; Tamura et al, 2016). Hepatocytes and hepatic stellate cells could also produce TNF‐α following IR‐injury.…”

“…Recently, we have observed that treatment with GGsTop significantly reduces oxidative stress and formation of free radicals in the hepatic tissue that led to decreased IR-induced liver injury in healthy rats (Tamura et al, 2016). It is well known that serum γ-GT level increases in patients with non-alcoholic fatty liver disease as well as alcoholic liver disease (Sueyoshi et al, 2016).…”

“…No abnormalities were observed in behaviour, body weight and amount of food intake for 2 weeks after intravenous administration of GGsTop at a single dose of 30 or 100 mg·kg −1 in rats (Yamamoto et al, 2011). Recently, we have observed that treatment with GGsTop significantly reduces oxidative stress and formation of free radicals in the hepatic tissue that led to decreased IR‐induced liver injury in healthy rats (Tamura et al, 2016). It is well known that serum γ‐GT level increases in patients with non‐alcoholic fatty liver disease as well as alcoholic liver disease (Sueyoshi et al, 2016).…”

Crystal structures of glutathione- and inhibitor-bound human GGT1: critical interactions within the cysteinylglycine binding site

“…γ-glutamyl transpeptidase (GGT1, aka γglutamyl transferase) is a cell surface enzyme that cleaves extracellular glutathione (GSH), GSH Sconjugates, and other γ-glutamyl compounds (1,2). Overexpression of GGT1 contributes to the severity of a variety of pathological conditions including asthma, reperfusion injury, and cardiovascular disease (3)(4)(5)(6). It stimulates tumor growth and activates compounds including the chemotherapy drug cisplatin to nephrotoxins (7)(8)(9)(10)(11).…”