Adolfo Cruz

Melatonin reduces apoptosis and necrosis induced by ischemia/reperfusion injury of the pancreas.

Abstract:  The pancreas is highly susceptible to the oxidative stress induced by ischemia/reperfusion (IR) injury leading to the generation of acute pancreatitis. Melatonin has been shown to be useful in the prevention of the damage by ischemia‐reperfusion in liver, brain, myocardium, gut and kidney. The aim of the study was to evaluate the cytoprotective properties of melatonin against injury induced by IR in pancreas. The obstruction of gastro‐duodenal and inferior splenic arteries induced pancreatic IR in male Wistar rats. Melatonin was intraperitoneally administered before or/and after IR injury. The animals were killed at 24 and 48 hr after reperfusion and there were evaluated parameters of oxidative stress (lipoperoxides, superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione), glandular endocrine and exocrine function (lipase, amylase, insulin) and cell injury (apoptosis and necrosis). The IR induced a marked enhancement of oxidative stress and impaired pancreatic function. The histological analysis showed that IR induced acute pancreatitis with the accumulation of inflammatory infiltrate, disruption of tissue structure, cell necrosis and hemorrhage. Melatonin administration before or after pancreatic IR prevented all tissue markers of oxidative stress, biochemical and histological signs of apoptosis and necrosis, and restored glandular function. No histological signs of pancreatitis were observed 48 hr after reperfusion in 80% of the animals treated with melatonin, with only a mild edematous pancreatitis being observed in the remaining rats. Preventive or therapeutic administration of melatonin protected against the induction of oxidative stress and tissue injury, and restored cell function in experimental pancreatic IR in rats.

Melatonin Prevents Oxidative Stress and Hepatocyte Cell Death Induced by Experimental Cholestasis

The induction of oxidative stress precedes liver injury during experimental obstructive jaundice (OJ). In this sense, different evidences suggest that melatonin (MEL), as antioxidant, may be useful in the protection against apoptosis and necrosis during experimental cholestasis. In addition, we will also assess if MEL-dependent protection is related to a recovery of antioxidant status disturbances induced by OJ. Cholestasis was achieved by double ligature and sectioning of the principal bile duct. MEL was injected intraperitoneally (500 μg/kg/day). Lipid peroxidation was evaluated by the measurement of malondialdehyde (MDA) content in liver. Different parameters related to antioxidant status, such as reduced glutathione (GSH), glutathione peroxidase (GPx), catalase and superoxide dismutase (SOD) were determined in liver. Liver injury was assessed by alanine aminotransferase (ALT) in serum, histological examination, DNA fragmentation and TUNEL assay. The activation of perisinusoidal stellate cells was evaluated by immunohistochemical measurement of α-smooth muscle actin in liver sections. The induction of OJ increased all the parameters related to apoptosis and necrosis in liver. The induction of liver injury was associated with stellate cell activation, as well as an increase in MDA (p<0.0001) and a reduction in GSH, GPx, catalase and SOD content (p<0.0001) in liver. MEL reduced hepatic apoptosis and necrosis (p<0.004) with a significant improvement in all oxidative stress markers. In conclusion, our results showed that MEL recovered the antioxidant status and reduced apoptosis and necrosis induced by experimental cholestasis.

Melatonin prevents experimental liver cirrhosis induced by thioacetamide in rats

Abstract:  Liver cirrhosis is a critical stage of chronic liver diseases that can produce liver failure, portal hypertension and hepatocarcinoma. Sustained oxidative stress plays a key role in cell damage and fibrosis induced during liver cirrhosis. We evaluated the effect of oxidative stress regulation by melatonin on the development of parenchymal destruction and stellate cell activation in experimental liver cirrhosis. Melatonin was administered to rats with liver cirrhosis induced by thioacetamide (TAA) for 1 or 3 months. Liver injury was assessed by serological analysis, as well as hematoxylin‐eosin staining and the in situ apoptosis detection assay in liver sections. Oxidative stress was evaluated by lipoperoxide and reduced glutathione levels, and by the measurement of catalase and superoxide dismutase activities in liver and serum respectively. The activation of stellate cells was evaluated by α‐smooth muscle actin expression in liver sections. Our results showed that TAA induced oxidative stress with extensive tissue damage and enhanced α‐smooth muscle actin expression in liver. Melatonin prevented the oxidative stress‐related changes associated with TAA toxicity. In conclusion, the study showed that melatonin prevents the tissue damage and fibrosis associated with TAA‐induced liver cirrhosis in rats.

Melatonin protects against renal oxidative stress after obstructive jaundice in rats.

The goals of this study were to analyze the renal oxidative status in experimental biliary obstruction and to evaluate the impact of melatonin on renal oxidative stress. Cholestasis was done by double ligature and section of the extra-hepatic biliary duct. Melatonin was injected i.p. (500 microg/kg/day). Malondialdehyde, reduced glutathione, catalase, superoxide dismutase, glutathione reductase, glutathione peroxidase and glutathione transferase were determined in the renal tissue. After biliary obstruction, an increase in malondialdehyde (P<0.0001) and a fall in reduced glutathione (P<0.0001) were seen. Moreover, the scavenger enzyme activity had significantly diminished. After melatonin administration, the malondialdehyde fell significantly (P<0.0001), whereas reduced glutathione showed an important increase (P<0.0001) compared with the ligated bile duct group. Experimental bile duct obstruction was associated to an increase of renal oxidative stress. Treatment with melatonin decreased the renal lipid peroxidation, and both the reduced glutathione as well as the scavenger enzyme activity recovered.

Melatonin and celecoxib improve the outcomes in hamsters with experimental pancreatic cancer

Abstract:  Pancreatic cancer is a major health problem because of the aggressiveness of the disease and the lack of effective systemic therapies. Melatonin (MEL) has antioxidant activity and prevents experimental genotoxicity. The specific inhibitor of cyclooxygenase‐2 (COX‐2), celecoxib (CEL), increases the efficacy of chemoradiotherapy in advanced pancreatic cancer. The objective of the study was the comparison and synergic effect of MEL and CEL during either the induction or progression phases of the tumor process, measuring parameters of oxidative stress, number of tumor nodules and survival of animals with pancreatic cancer. Pancreatic cancer was induced by N‐nitrosobis (2‐oxopropyl)amine) (BOP) in Syrian hamsters. Melatonin and/or CEL were administered during the induction, postinduction as well as during both phases. The presence of tumor nodules were observed macroscopically in pancreatic and splenic areas, and the levels of lipoperoxides (LPO), reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH‐Px) in pancreatic tissue were measured. The increases in tumor nodules and LPO as well as the reductions in GSH and enzymatic antioxidants in the pancreas induced by BOP were related to a lower survival rate of animals. The administration of MEL exerted a more potent beneficial effect than CEL treatment on the reduction in tumor nodules, oxidative stress and death of experimental BOP‐treated animals. The combined treatment only exerted a synergistic beneficial effect when administered during the induction phase. Melatonin by itself had significant beneficial actions in improving the survival of hamsters.

Beneficial properties of melatonin in an experimental model of pancreatic cancer

Abstract:  Pancreatic cancer is a major health problem because of the aggressiveness of the disease and the lack of effective systemic therapies. Melatonin has antioxidant activity and prevents experimental genotoxicity. However, the effect of melatonin in pancreatic cancer has not been tested. Pancreatic carcinogenesis was induced by N‐nitrosobis (2‐oxopropyl)amine (BOP) in Syrian hamsters. Melatonin was administered during the BOP‐induction phase (12 wk) and/or following the postinduction phase (12 wk). Different parameters of oxidative stress including lipid peroxides (LPO) and antioxidants (superoxide dismutase, catalase, reduced glutathione and glutathione peroxidase) were determined in pancreatic tissue. Also, the presence of atypical hyperplasia (AH), well and moderately differentiated adenomacarcinoma (ADC‐WD and ADC‐MD, respectively) were studied. The administration of BOP induced an intense oxidative stress and ADC induction in the pancreas. The administration of melatonin during the induction or postinduction phase reduced LPO and improved the antioxidant status, as well as drastically reducing the presence of ADC but some AH remained. In conclusion, treatment with melatonin reduced oxidative damage and cancer nodules induced by BOP in the pancreas.

Melatonin prevents brain oxidative stress induced by obstructive jaundice in rats

The aim of the study was to analyze the impact of melatonin on brain oxidative stress in experimental biliary obstruction. Cholestasis was done by a double ligature and section of the extrahepatic biliary duct. Melatonin was injected intraperitoneally (500 μg/kg/day). Malondialdehyde (MDA), reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) contents were determined in the brain tissue. Biliary obstruction raised MDA and reduced GSH contents in the cortex, cerebellum, and hypothalamus areas. Moreover, the scavenger enzyme activity significantly dropped in all areas of the brain. Melatonin drastically reduced MDA concentration and enhanced GSH concentration, as well as all antioxidant enzyme activity in all brain areas obtained from the bile duct–ligated animals. In conclusion, the treatment with melatonin decreased lipid peroxidation and recovered the antioxidant status in the brain from cholestatic animals.

Nitric oxide mimics transcriptional and post-translational regulation during α-Tocopherol cytoprotection against glycochenodeoxycholate-induced cell death in hepatocytes

BACKGROUND & AIMS Reactive oxygen species (ROS) and nitric oxide (NO) exert a relevant role during bile acid-induced hepatotoxicity. Whether α-Tocopherol regulates oxidative and nitrosative stress, bile acid transporter expression and their NO-dependent post-translational modifications, and cell death were assessed in vitro and in vivo. METHODS α-Tocopherol and/or NO donors (DETA-NONOate or CSNO, and V-PYRRO/NO) were administered to glycochenodeoxycholic acid (GCDCA)-treated cultured human hepatocytes or to bile duct obstructed rats. Cell injury, superoxide anion (O⁻₂) production, as well as inducible nitric oxide synthase (NOS-2), cytochrome P4507A1 (CYP7A1), heme oxygenase-1, (HO-1) and bile acid transporter expression were determined. Cysteine S-nitrosylation and tyrosine nitration of Na(+)-taurocholate co-transporting polypeptide (NTCP), as well as taurocholic acid (TC) uptake were also evaluated. RESULTS GCDCA-induced cell death was associated with increased (O⁻₂) production, NTCP and HO-1 expression, and with a reduction of CYP7A1 and NOS-2 expression. α-Tocopherol reduced cell death, (O⁻₂) production, CYP7A1, NTCP, and HO-1 expression, as well as increased NOS-2 expression and NO production in GCDCA-treated hepatocytes. α-Tocopherol and NO donors increased NTCP cysteine S-nitrosylation and tyrosine nitration, and reduced TC uptake in hepatocytes. α-Tocopherol and V-PYRRO/NO reduced liver injury and NTCP expression in obstructed rats. CONCLUSIONS The regulation of CYP7A1, NTCP, and HO-1 expression may be relevant for the cytoprotective properties of α-Tocopherol and NO against mitochondrial dysfunction, oxidative stress and cell death in GCDCA-treated hepatocytes. The regulation of NO-dependent post-translational modifications of NTCP by α-Tocopherol and NO donors reduces the uptake of toxic bile acids by hepatocytes.

Melatonin exerts a more potent effect than S-adenosyl-l-methionine against iron metabolism disturbances, oxidative stress and tissue injury induced by obstructive jaundice in rats

Melatonin and S-adenosyl-l-methionine (SAMe) prevent oxidative stress and tissue dysfunction in obstructive jaundice (OJ). Lipid peroxidation is exacerbated in the presence of trace amounts of iron (Fe). The study investigated the regulation by melatonin and SAMe the induction of oxidative stress, iron metabolism disturbances and tissue injury in an experimental model of OJ. Different parameters of lipid peroxidation, antioxidant status, tissue injury and Fe metabolism were determined in liver and blood. OJ induced Fe accumulation in liver, and increased transferrin (Tf) saturation and loosely bound Fe content in blood. Melatonin, and SAMe at lesser extent, enhanced protein Tf content in liver and blood, that reduced loosely bound Fe content in blood. Melatonin and SAMe did not affect ferritin (FT) and Tf mRNA expression, but reduced Tf receptor (TfR) mRNA expression in liver. In conclusion, the effect of melatonin and SAMe on Fe metabolism may be included in the beneficial properties of these agents on lipid peroxidation and tissue injury induced by OJ.

Alteration of the renal regulatory hormonal pattern during experimental obstructive jaundice

OBJECTIVE The alteration of hormones regulating sodium and water status is related to renal failure in obstructive jaundice (OJ). EXPERIMENTAL DESIGN OJ was induced by common bile duct ligation. Samples were obtained from the control (SO) and OJ groups at 24 and 72 hours, and at 7 days. Different parameters related to biliary obstruction, liver and renal injury, and vasoactive mediators such as renin, aldosterone, endothelin-1 (ET-1) and prostaglandin E2 (PGE2) were studied. RESULTS Bile duct ligation caused an increase in total bilirubin (p < 0.001) and alkaline phosphatase (AP) (p < 0.001). The SO and OJ groups had the same values for diuresis, renin, and creatinine clearance at 24 h. However, animals with OJ had a lower sodium concentration in urine than SO animals (p < 0.01), as well as an increase in aldosterone levels (p < 0.03). ANP levels were moderately increased during OJ but did not reach statistical significance when compared to the SO group. In contrast, OJ animals showed a rise in serum ET-1 concentration (p < 0.001) and increased PGE2 in urine (p < 0.001). CONCLUSIONS Biliary obstruction induced an increase in ET-1 release and PGE2 urine excretion. These hormones might play a role during the renal complications associated with renal disturbances that occur during OJ.