Ultrastructural clues for the protective effect of melatonin against oxidative damage in cerulein-induced pancreatitis

Interleukin‑22 alleviates arginine‑induced pancreatic acinar cell injury via the regulation of intracellular vesicle transport system: Evidence from proteomic analysis

Acute pancreatitis (AP) is a severe inflammatory condition characterized by the activation of pancreatic enzymes within acinar cells, leading to tissue damage and inflammation. Interleukin (IL)-22 is a potential therapeutic agent for AP owing to its anti-inflammatory properties and ability to promote tissue repair. The present study evaluated the differentially expressed proteins in arginine-induced pancreatic acinar cell injury following treatment with IL-22, and the possible mechanisms involved in IL-22-mediated alleviation of AP. AR42J cells were stimulated using L-arginine to establish an acinar cell injury model in vitro and the damaged cells were subsequently treated with IL-22. The characteristics of the model and the potential therapeutic effects of IL-22 were examined by CCK-8 assay, flow cytometry, TUNEL assay, transmission electron microscopy and ELISA. Differentially expressed proteins in cells induced by arginine and treated with IL-22 were assessed using liquid chromatography-mass spectrometry. The identified proteins were further subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis to elucidate their functional roles. The present study demonstrated that arginine-stimulated cells showed significant pathological changes resembling those in AP, which were alleviated after IL-22 treatment. Proteomic analysis then demonstrated that in IL-22-treated cells, proteins related to the formation and fusion of autophagosomes with lysosomes were significantly downregulated, whereas endocytosis related proteins were enriched in the upregulated proteins. After IL-22 treatment, western blotting demonstrated reduced expression of autophagy-associated proteins. In conclusion, by inhibiting the formation and fusion of autophagosomes with lysosomes, IL-22 may have mitigated premature trypsinogen activation, subsequently minimizing acinar cell injury induced by L-arginine. This was accompanied by concurrent upregulation of endocytosis, which serves a pivotal role in sustaining regular cellular material transport and signal propagation. This research underscored the potential of IL-22 in mitigating arginine-induced AR42J injury, which could be valuable in refining treatment strategies for AP.

St13 protects against disordered acinar cell arachidonic acid pathway in chronic pancreatitis

BACKGROUND

Early diagnosis and treatment of chronic pancreatitis (CP) are limited. In this study, St13, a co-chaperone protein, was investigated whether it constituted a novel regulatory target in CP. Meanwhile, we evaluated the value of micro-PET/CT in the early diagnosis of CP.

METHODS

Data from healthy control individuals and patients with alcoholic CP (ACP) or non-ACP (nACP) were analysed. PRSS1 transgenic mice (PRSS1^Tg) were treated with ethanol or caerulein to mimic the development of ACP or nACP, respectively. Pancreatic lipid metabolite profiling was performed in human and PRSS1^Tg model mice. The potential functions of St13 were investigated by crossing PRSS1^Tg mice with St13^-/- mice via immunoprecipitation and lipid metabolomics. Micro-PET/CT was performed to evaluate pancreatic morphology and fibrosis in CP model.

RESULTS

The arachidonic acid (AA) pathway ranked the most commonly dysregulated lipid pathway in ACP and nACP in human and mice. Knockout of St13 exacerbated fatty replacement and fibrosis in CP model. Sdf2l1 was identified as a binding partner of St13 as it stabilizes the IRE1α-XBP1s signalling pathway, which regulates COX-2, an important component in AA metabolism. Micro-PET/CT with ⁶⁸Ga-FAPI-04 was useful for evaluating pancreatic morphology and fibrosis in CP model mice 2 weeks after modelling.

CONCLUSION

St13 is functionally activated in acinar cells and protects against the cellular characteristics of CP by binding Sdf2l1, regulating AA pathway. ⁶⁸Ga-FAPI-04 PET/CT may be a very valuable approach for the early diagnosis of CP. These findings thus provide novel insights into both diagnosis and treatment of CP.

Effect of acetyl-L-carnitine on hypersensitivity in acute recurrent caerulein-induced pancreatitis and microglial activation along the brain’s pain circuitry

BACKGROUND

Acute pancreatitis (AP) and recurring AP are serious health care problems causing excruciating pain and potentially lethal outcomes due to sepsis. The validated caerulein- (CAE) induced mouse model of acute/recurring AP produces secondary persistent hypersensitivity and anxiety-like behavioral changes for study.

AIM

To determine efficacy of acetyl-L-carnitine (ALC) to reduce pain-related behaviors and brain microglial activation along the pain circuitry in CAE-pancreatitis.

METHODS

Pancreatitis was induced with 6 hly intraperitoneal (i.p.) injections of CAE (50 µg/kg), 3 d a week for 6 wk in male C57BL/6J mice. Starting in week 4, mice received either vehicle or ALC until experiment’s end. Mechanical hyper-sensitivity was assessed with von Frey filaments. Heat hypersensitivity was determined with the hotplate test. Anxiety-like behavior was tested in week 6 using elevated plus maze and open field tests. Microglial activation in brain was quantified histologically by immunostaining for ionized calcium-binding adaptor molecule 1 (Iba1).

RESULTS

Mice with CAE-induced pancreatitis had significantly reduced mechanical withdrawal thresholds and heat response latencies, indicating ongoing pain. Treatment with ALC attenuated inflammation-induced hypersensitivity, but hypersensitivity due to abdominal wall injury caused by repeated intraperitoneal injections persisted. Animals with pancreatitis displayed spontaneous anxiety-like behavior in the elevated plus maze compared to controls. Treatment with ALC resulted in increased numbers of rearing activity events, but time spent in “safety” was not changed. After all the abdominal injections, pancreata were translucent if excised at experiment’s end and opaque if excised on the subsequent day, indicative of spontaneous healing. Post mortem histopathological analysis performed on pancreas sections stained with Sirius Red and Fast Green identified wide-spread fibrosis and acinar cell atrophy in sections from mice with CAE-induced pancreatitis that was not rescued by treatment with ALC. Microglial Iba1 immunostaining was significantly increased in hippocampus, thalamus (intralaminar nuclei), hypothalamus, and amygdala of mice with CAE-induced pancreatitis compared to naïve controls but unchanged in the primary somatosensory cortex compared to naïves.

CONCLUSION

CAE-induced pancreatitis caused increased pain-related behaviors, pancreatic fibrosis, and brain microglial changes. ALC alleviated CAE-induced mechanical and heat hypersensitivity but not abdominal wall injury-induced hypersensitivity caused by the repeated injections.

Superoxide Dismutase Predicts Persistent Circulation Failure and Mortality in the Early Stage of Acute Pancreatitis

OBJECTIVES

Oxidative stress is an important event in the pathogenesis of acute pancreatitis. Superoxide dismutase is a major antioxidant enzyme in the body. The aim of this study was to investigate the changes in superoxide dismutase activity early in the onset of acute pancreatitis and its value in predicting the risk of organ failure and mortality.

METHODS

Data for 2549 patients hospitalized from 2013 to 2017 were extracted from the prospective database, and we selected 854 adult patients who were admitted within 24 h of disease onset with complete data. Serum superoxide dismutase activities on the first, second, and third days of hospital admission for patients with different severities, organ failure, and mortality were compared. The areas under the curve for the prediction of organ failure, pancreatic necrosis, and mortality were estimated using receiver operating characteristic curves.

RESULTS

Among the 854 adult patients, superoxide dismutase activities were significantly different among patients with mild acute pancreatitis, moderately severe acute pancreatitis, and severe acute pancreatitis (P = 0.005). Superoxide dismutase activity was significantly decreased in patients with persistent renal failure (77.8 ± 37.2), persistent circulatory failure (66.2 ± 14.9), and mortality (64.3 ± 16.0). The accuracy of superoxide dismutase with regard to predicting persistent circulatory failure and mortality was high, and the areas under the receiver operating characteristic curves were 0.83 and 0.84, respectively.

CONCLUSIONS

Superoxide dismutase activity was negatively correlated with the severity and clinical outcome of AP. Superoxide dismutase activity is highly accurate at predicting persistent circulation failure and mortality in the early stage of AP.

Stem cell therapy: a potential for the perils of pancreatitis

Acute and chronic pancreatitis carry a significant disease burden and there is no definite treatment that exists for either. They are associated with local and systemic inflammation and lead to numerous complications. Stem cell therapy has been explored for other disease processes and is a topic of research that has gained momentum with regards to implications for acute and chronic pancreatitis. They not only carry the potential to aid in regeneration but also prevent pancreatic injury as well as injury of other organs and hence the resultant complications. Stem cells appear to have immunomodulatory properties and clinical potential as evidenced by numerous studies in animal models. This review article discusses the types of stem cells commonly used and the properties that show promise in the field of pancreatitis.

ATF6 aggravates acinar cell apoptosis and injury by regulating p53/AIFM2 transcription in Severe Acute Pancreatitis

Background: There is no curative therapy for severe acute pancreatitis (SAP) due to poor understanding of its molecular mechanisms. Endoplasmic reticulum (ER) stress is involved in SAP and increased expression of ATF6 has been detected in SAP patients. Here, we aimed to investigate the role of ATF6 in a preclinical SAP mouse model and characterize its regulatory mechanism. Methods: Pancreatic tissues of healthy and SAP patients were collected during surgery. Humanized PRSS1 transgenic mice were treated with caerulein to mimic the SAP development, which was crossed to an ATF6 knockout mouse line, and pancreatic tissues from the resulting pups were screened by proteomics. Adenovirus-mediated delivery to the pancreas of SAP mice was used for shRNA-based knockdown or overexpression. The potential functions and mechanisms of ATF6 were clarified by immunofluorescence, immunoelectron microscopy, Western blotting, qRT-PCR, ChIP-qPCR and luciferase reporter assay. Results: Increased expression of ATF6 was associated with elevated apoptosis, ER and mitochondrial disorder in pancreatic tissues from SAP patients and PRSS1 mice. Knockout of ATF6 in SAP mice attenuated acinar injury, apoptosis and ER disorder. AIFM2, known as a p53 target gene, was identified as a downstream regulatory partner of ATF6, whose expression was increased in SAP. Functionally, AIFM2 could reestablish the pathological disorder in SAP tissues in the absence of ATF6. p53 expression was also increased in SAP mice, which was downregulated by ATF6 knockout. p53 knockout significantly suppressed acinar apoptosis and injury in SAP model. Mechanistically, ATF6 promoted AIFM2 transcription by binding to p53 and AIFM2 promoters. Conclusion: These results reveal that ATF6/p53/AIFM2 pathway plays a critical role in acinar apoptosis during SAP progression, highlighting novel therapeutic target molecules for SAP.

N-Acetylcysteine enhances the therapeutic efficacy of bone marrow-derived mesenchymal stem cell transplantation in rats with severe acute pancreatitis

BACKGROUND

Severe acute pancreatitis (SAP) is a high mortality disease, for which there is a lack of effective therapies. Previous research has demonstrated that bone marrow-derived mesenchymal stem cells (BMSCs), which have immunomodulatory and antioxidant properties, have potential for the treatment of SAP. It remains unclear, however, whether the free radical scavenger N-acetylcysteine (NAC) can enhance the therapeutic efficacy of BMSC transplantation in SAP. In this study, we investigated the effect of combining treatment with NAC and BMSCs in a rat model of SAP.

METHODS

SAP was induced by injection of sodium taurocholate into the pancreatic duct and, after successful induction of SAP, the rats were treated with BMSCs and NAC, either singly or in combination.

RESULTS

After 3 days, serum levels of amylase, proinflammatory factors, malondialdehyde, and reactive oxygen species were significantly decreased in animals treated with BMSCs or NAC, compared with vehicle-treated animals. In contrast, total glutathione, superoxide dismutase and catalase were markedly increased after treatment with BMSCs or NAC. However, oxidative stress markers and inflammatory factors were significantly improved in the SAP + BMSCs + NAC group compared with those in the SAP + NAC group and the SAP + BMSCs group.

CONCLUSIONS

Combined NAC and BMSC therapy was found to alleviate oxidative stress damage to the pancreas and to inhibit the inflammatory response to a significantly greater extent than single therapy with either BMSCs or NAC. Because NAC enhances the therapeutic efficacy of BMSC transplantation in a rat model of SAP, combined therapy may provide a promising new approach for the treatment of SAP.

Diplomats' Mystery Illness and Pulsed Radiofrequency/Microwave Radiation

Importance: A mystery illness striking U.S. and Canadian diplomats to Cuba (and now China) "has confounded the FBI, the State Department and US intelligence agencies" (Lederman, Weissenstein, & Lee, 2017). Sonic explanations for the so-called health attacks have long dominated media reports, propelled by peculiar sounds heard and auditory symptoms experienced. Sonic mediation was justly rejected by experts. We assessed whether pulsed radiofrequency/microwave radiation (RF/MW) exposure can accommodate reported facts in diplomats, including unusual ones. Observations: (1) Noises: Many diplomats heard chirping, ringing or grinding noises at night during episodes reportedly triggering health problems. Some reported that noises were localized with laser-like precision or said the sounds seemed to follow them (within the territory in which they were perceived). Pulsed RF/MW engenders just these apparent "sounds" via the Frey effect. Perceived "sounds" differ by head dimensions and pulse characteristics and can be perceived as located behind in or above the head. Ability to hear the "sounds" depends on high-frequency hearing and low ambient noise. (2) Signs/symptoms: Hearing loss and tinnitus are prominent in affected diplomats and in RF/MW-affected individuals. Each of the protean symptoms that diplomats report also affect persons reporting symptoms from RF/MW: sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each. Both encompass vision, balance, and speech problems and nosebleeds. Brain injury and brain swelling are reported in both. (3) Mechanisms: Oxidative stress provides a documented mechanism of RF/MW injury compatible with reported signs and symptoms; sequelae of endothelial dysfunction (yielding blood flow compromise), membrane damage, blood-brain barrier disruption, mitochondrial injury, apoptosis, and autoimmune triggering afford downstream mechanisms, of varying persistence, that merit investigation. (4) Of note, microwaving of the U.S. embassy in Moscow is historically documented. Conclusions and relevance: Reported facts appear consistent with pulsed RF/MW as the source of injury in affected diplomats. Nondiplomats citing symptoms from RF/MW, often with an inciting pulsed-RF/MW exposure, report compatible health conditions. Under the RF/MW hypothesis, lessons learned for diplomats and for RF/MW-affected civilians may each aid the other.

Ceruloplasmin and hephaestin jointly protect the exocrine pancreas against oxidative damage by facilitating iron efflux

Little is known about the iron efflux from the pancreas, but it is likely that multicopper ferroxidases (MCFs) are involved in this process. We thus used hephaestin (Heph) and ceruloplasmin (Cp) single-knockout mice and Heph/Cp double-knockout mice to investigate the roles of MCFs in pancreatic iron homeostasis. We found that both HEPH and CP were expressed in the mouse pancreas, and that ablation of either MCF had limited effect on the pancreatic iron levels. However, ablation of both MCFs together led to extensive pancreatic iron deposition and severe oxidative damage. Perls’ Prussian blue staining revealed that this iron deposition was predominantly in the exocrine pancreas, while the islets were spared. Consistent with these results, plasma lipase and trypsin were elevated in Heph/Cp knockout mice, indicating damage to the exocrine pancreas, while insulin secretion was not affected. These data indicate that HEPH and CP play mutually compensatory roles in facilitating iron efflux from the exocrine pancreas, and show that MCFs are able to protect the pancreas against iron-induced oxidative damage.

Melatonin Regulates Apoptosis and Autophagy Via ROS-MST1 Pathway in Subarachnoid Hemorrhage

Compelling evidence has indicated that imbalance between apoptosis and autophagy may be involved in subarachnoid hemorrhage (SAH). We aimed to investigate the effects and mechanisms of melatonin in the homeostasis of apoptosis and autophagy. One-hundred and forty-eight male Sprague-Dawley rats were intraperitoneally injected with melatonin or vehicle 2 h after SAH induction. Western blotting and an immunofluorescent assay were performed to detect the expression of apoptosis- and autophagy-related proteins. The neuroprotective effect of melatonin attenuating SAH-induced neurological deficit and brain edema may be associated with the suppression of SAH-induced neuronal apoptosis and autophagy. Furthermore, melatonin inhibited the cleavage of mammalian sterile 20-like kinase 1 (MST1) protein by reducing reactive oxygen species (ROS) content. These effects of melatonin on regulating the homeostasis between apoptosis and autophagy could be reversed by an MST1 agonist, chelerythrine, via enhancement of MST1 cleavage. In conclusion, exogenous melatonin alleviates SAH-induced early brain injury (EBI) by suppressing excessive neuronal apoptosis and autophagy. The underlying mechanism may, at least in part, involve the ROS-MST1 pathway.

Effects of Melatonin and Its Analogues on Pancreatic Inflammation, Enzyme Secretion, and Tumorigenesis

Melatonin is an indoleamine produced from the amino acid l-tryptophan, whereas metabolites of melatonin are known as kynuramines. One of the best-known kynuramines is N¹-acetyl-N¹-formyl-5-methoxykynuramine (AFMK). Melatonin has attracted scientific attention as a potent antioxidant and protector of tissue against oxidative stress. l-Tryptophan and kynuramines share common beneficial features with melatonin. Melatonin was originally discovered as a pineal product, has been detected in the gastrointestinal tract, and its receptors have been identified in the pancreas. The role of melatonin in the pancreatic gland is not explained, however several arguments support the opinion that melatonin is probably implicated in the physiology and pathophysiology of the pancreas. (1) Melatonin stimulates pancreatic enzyme secretion through the activation of entero-pancreatic reflex and cholecystokinin (CCK) release. l-Tryptophan and AFMK are less effective than melatonin in the stimulation of pancreatic exocrine function; (2) Melatonin is a successful pancreatic protector, which prevents the pancreas from developing of acute pancreatitis and reduces pancreatic damage. This effect is related to its direct and indirect antioxidant action, to the strengthening of immune defense, and to the modulation of apoptosis. Like melatonin, its precursor and AFMK are able to mimic its protective effect, and it is commonly accepted that all these substances create an antioxidant cascade to intensify the pancreatic protection and acinar cells viability; (3) In pancreatic cancer cells, melatonin and AFMK activated a signal transduction pathway for apoptosis and stimulated heat shock proteins. The role of melatonin and AFMK in pancreatic tumorigenesis remains to be elucidated.

Snapshot: implications for melatonin in endoplasmic reticulum homeostasis

The endoplasmic reticulum (ER) is an important intracellular membranous organelle. Previous studies have demonstrated that the ER is responsible for protein folding and trafficking, lipid synthesis and the maintenance of calcium homeostasis. Interestingly, the morphology and structure of the ER were recently found to be important. Melatonin is a hormone that anticipates the daily onset of darkness in mammals, and it is well known that melatonin acts as an antioxidant by scavenging free radicals and increasing the activity of antioxidant enzymes in the body. Notably, the existing evidence demonstrates that melatonin is involved in ER homeostasis, particularly in the morphology of the ER, indicating a potential protective role of melatonin. This review discusses the existing knowledge regarding the implications for the involvement of melatonin in ER homeostasis.

Effects of melatonin on the acute inflammatory response associated with endoscopic retrograde cholangiopancreatography: A randomized, double-blind, placebo-controlled trial

INTRODUCTION

Endoscopic retrograde cholangiopancreatography (ERCP) is associated with an acute inflammatory response and melatonin has a variety of immunomodulatory and antioxidant effects studied experimentally in pancreatobiliary pathology.

AIMS

The aim of our study was to evaluate the effects of peri-procedural administration of melatonin on the inflammatory response and lipid peroxidation associated with ERCP.

METHODS

In this proof-of-concept clinical trial, 37 patients with a high probability of choledocholithiasis were randomized to receive peri-procedure (ERCP) melatonin or placebo. We measured the serum concentration of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), vascular endothelial growth factor (VEGF), lipid peroxidation, amylase, and liver function tests 24h before and after the procedure.

RESULTS

We found no pre-procedure or post-procedure differences between the melatonin group or the placebo group (P>.05) in the serum concentrations of TNF-alpha (melatonin: 153.8 vs. 149.4ng/m; placebo: 103.5 vs. 107.3ng/ml), IL-6 (melatonin: 131.8 vs. 133.3ng/ml; placebo: 177.8 vs. 197.8ng/ml), or VEGF (melatonin: 157.3 vs. 157.8pg/ml; placebo: 97.3 vs. 97.8pg/ml), or in relation to lipid peroxidation (melatonin: 39.2 vs. 72.3μg/ml; placebo: 66.4 vs. 90.5μg/ml). After ERCP, a significant decrease in the AST, ALT, and total bilirubin levels was found only in the melatonin group (P<.05). The administration of melatonin was safe and tolerable.

CONCLUSIONS

Melatonin is safe and tolerable in patients undergoing ERCP, but it does not appear to affect inflammatory cytokine concentrations or lipid peroxidation.

Melatonin is more effective than ascorbic acid and β-carotene in improvement of gastric mucosal damage induced by intensive stress

INTRODUCTION

Oxidative stress has been considered to play a primary role in the pathogenesis of stress-induced gastric damage. The aim of this study was to investigate the effects of melatonin, ascorbic acid and β-carotene on stress-induced gastric mucosal damage.

MATERIAL AND METHODS

Fifty-six male Wistar albino rats were divided into control, stress, stress + standard diet, stress + saline, stress + melatonin, stress + ascorbic acid and stress + β-carotene groups. The rats from stress groups were exposed to starvation, immobilization and cold by immobilizing for 8 h at +4°C following 72-hour food restriction. Following stress application, melatonin, ascorbic acid and β-carotene were administered for 7 days. Specimens of gastric tissue were prepared for microscopic and biochemical examinations.

RESULTS

Mean histopathological damage scores and mean tissue malondialdehyde levels were significantly decreased but mean tissue glutathione levels and glutathione peroxidase and superoxide dismutase activities were increased in treatment groups vs. stress groups in general. Mean histopathological damage scores of the stress + Mel group was lower than those of stress + D, stress + S, stress + β-car (p < 0.05) and stress + Asc groups (p < 0.005). Additionally, mean tissue catalase activity of the stress + Mel group was higher than that of stress + S (p < 0.005), stress + D (p < 0.05) and stress + β-car groups (p < 0.05).

CONCLUSIONS

Melatonin is more effective than ascorbic acid and β-carotene in improvement of gastric damage induced by intensive stress. We suggest that as well as the direct antioxidant and free radical scavenging potency of melatonin, its indirect effect via the brain-gut axis might account for its greater beneficial action against stress-induced gastric damage.

Melatonin enhances the occurrence of autophagy induced by oxidative stress in Arabidopsis seedlings

The beneficial effect that melatonin has against mitochondrial dysfunctioning seems to be linked to mitophagy. Roles for melatonin have been demonstrated in promoting health and preventing disease, as well as activating the process of autophagy in general. However, no reports have been made about how the application of melatonin regulates that process when plants are exposed to oxidative stress. We investigated the influence of different concentrations of melatonin (0.0, 0.5, 5.0, 10.0, or 50.0 μm) on autophagy under methyl viologen (MV)-induced oxidative stress. Arabidopsis seedlings that were pretreated with 5 or 10 μm melatonin underwent relatively strong induction of autophagy, as evidenced by the number of monodansylcadaverine (MDC)-stained autophagosomes in root samples. Pretreatment with 10 μm melatonin also alleviated MV-induced photo-oxidation damage and significantly reduced the accumulation of oxidized proteins. Those responses might have been due to the strong upregulation of genes that involved in AtATG8-PE conjugation pathway, which enhanced the capacity for autophagy. Histochemical staining revealed that both O2-· and H2 O2 were highly accumulated upon MV exposure, although the response did not differ significantly between control and melatonin-pretreated seedlings. By contrast, exogenous melatonin upregulated the expression of two genes for H2 O2 -scavenging enzymes, that is, AtAPX1 and AtCATs. The activation of autophagy by melatonin without an alteration in ROS production may be part of a survival mechanism that is enhanced by melatonin after cellular damage. Therefore, it represents a second level of defense to remove damaged proteins when antioxidant activities are compromised.

Amelioration of streptozotocin-induced diabetic nephropathy by melatonin, quercetin, and resveratrol in rats

The role of oxygen radicals are known for the pathogenesis of kidney damage. The aim of the present study was to investigate the antioxidative effects of melatonin, quercetin, and resveratrol on streptozotocin (STZ)-induced diabetic nephropathy in rats. A total of 35 male Wistar rats were divided into 5 groups as follows: control, diabetes mellitus (DM), DM + melatonin, DM + quercetin, and DM + resveratrol. All the injections started on the same day of single-dose STZ injection and continued for 30 days. At the end of this period, kidneys were removed and processed for routine histological procedures. Biochemical parameters and morphological changes were examined. In DM group, blood glucose levels were significantly increased, whereas body weights were decreased compared with the control group. Significant increases in blood urea nitrogen and tissue malondialdehyde (MDA) levels and decreases in superoxide dismutase and catalase activities were detected in DM group. Administration of melatonin, quercetin, and resveratrol significantly reduced these values. Melatonin was more efficient in reducing MDA levels than other antioxidants ( p < 0.05). STZ-induced histopathological alterations including epithelial desquamation, swelling, intracytoplasmic vacuolization, brush border loss and peritubular infiltration. Additionally, basement membrane thickening and sclerotic changes were observed in glomerulus. Transforming growth factor-β1 positive cells were also increased. Melatonin, quercetin, and resveratrol significantly reduced these histopathological changes. Our results indicate that melatonin, quercetin, and resveratrol might be helpful in reducing diabetes-induced renal damage

Melatonin-enhanced autophagy protects against neural apoptosis via a mitochondrial pathway in early brain injury following a subarachnoid hemorrhage

Melatonin is a strong antioxidant that has beneficial effects against early brain injury (EBI) following a subarachnoid hemorrhage (SAH) in rats; protection includes reduced mortality and brain water content. The molecular mechanisms underlying these clinical effects in the SAH model, however, have not been clearly identified. This study was undertaken to determine the influence of melatonin on neural apoptosis and the potential mechanism of these effects in EBI following SAH using the filament perforation model of SAH in male Sprague Dawley rats. Melatonin (150 mg/kg) or vehicle was given via an intraperitoneal injection 2 hr after SAH induction. Brain samples were extracted 24 hr after SAH. The results show that melatonin treatment markedly reduced caspase-3 activity and the number of TUNEL-positive cells, while the treatment increased the LC3-II/LC3-I, an autophagy marker, which indicated that melatonin-enhanced autophagy ameliorated apoptotic cell death in rats subjected to SAH. To further identify the mechanism of autophagy protection, we demonstrated that melatonin administration reduced Bax translocation to the mitochondria and the release of cytochrome c into the cytosol. Taken together, this report demonstrates that melatonin improved the neurological outcome in rats by protecting against neural apoptosis after the induction of filament perforation SAH; moreover, the mechanism of these antiapoptosis effects was related to the enhancement of autophagy, which ameliorated cell apoptosis via a mitochondrial pathway.

Central role of mitochondrial injury in the pathogenesis of acute pancreatitis

Acute pancreatitis is an inflammatory disease with no specific treatment. One of the main reasons behind the lack of specific therapy is that the pathogenesis of acute pancreatitis is poorly understood. During the development of acute pancreatitis, the disease-inducing factors can damage both cell types of the exocrine pancreas, namely the acinar and ductal cells. Because damage of either of the cell types can contribute to the inflammation, it is crucial to find common intracellular mechanisms that can be targeted by pharmacological therapies. Despite the many differences, recent studies revealed that the most common factors that induce pancreatitis cause mitochondrial damage with the consequent breakdown of bioenergetics, that is, ATP depletion in both cell types. In this review, we summarize our knowledge of mitochondrial function and damage within both pancreatic acinar and ductal cells. We also suggest that colloidal ATP delivery systems for pancreatic energy supply may be able to protect acinar and ductal cells from cellular damage in the early phase of the disease. An effective energy delivery system combined with the prevention of further mitochondrial damage may, for the first time, open up the possibility of pharmacological therapy for acute pancreatitis, leading to reduced disease severity and mortality.

Experimental and clinical evidence of antioxidant therapy in acute pancreatitis

Oxidative stress has been shown to play an important role in the pathogenesis of acute pancreatitis (AP). Antioxidants, alone or in combination with conventional therapy, should improve oxidative-stress-induced organ damage and therefore accelerate the rate of recovery. In recent years, substantial amounts of data about the efficiency of antioxidants against oxidative damage have been obtained from experiments with rodents. Some of these antioxidants have been found beneficial in the treatment of AP in humans; however, at present there is insufficient clinical data to support the benefits of antioxidants, alone or in combination with conventional therapy, in the management of AP in humans. Conflicting results obtained from experimental animals and humans may represent distinct pathophysiological mechanisms mediating tissue injury in different species. Further detailed studies should be done to clarify the exact mechanisms of tissue injury in human AP. Herein I tried to review the existing experimental and clinical studies on AP in order to determine the efficiency of antioxidants. The use of antioxidant enriched nutrition is a potential direction of clinical research in AP given the lack of clues about the efficiency and safety of antioxidant usage in patients with AP.

Melatonin-induced autophagy protects against human prion protein-mediated neurotoxicity

  Melatonin has neuroprotective effects in the models of neurodegenerative disease including Alzheimer's and Parkinson's disease. Several studies have shown that melatonin prevents neurodegeneration by regulation of mitochondrial function. However, the protective action of melatonin has not been reported in prion disease. We investigated the influence of melatonin on prion-mediated neurotoxicity. Melatonin rescued neuronal cells from PrP(106-126)-induced neurotoxicity by prevention of mitochondrial dysfunction. Moreover, the protective effect of melatonin against mitochondrial dysfunction was related with autophagy activation. Melatonin-treated cells were dose-dependently increased in LC3-II, an autophagy marker. Melatonin-induced autophagy prevented a PrP(106-126)-induced reduction in mitochondrial potential and translocation of Bax to the mitochondria and cytochrome c release. On the other hand, downregulation of autophagy protein 5 with Atg5 siRNA or the autophagy blocker 3-methyladenine prevented the melatonin-mediated neuroprotective effects. This is the first report demonstrating that treatment with melatonin appears to protect against prion-mediated neurotoxicity and that the neuroprotection is induced by melatonin-mediated autophagy signals. The results of this study suggest that regulation of melatonin is a therapeutic strategy for prion peptide-induced apoptosis.

Protective effect of melatonin on acute pancreatitis

Melatonin, a product of the pineal gland, is released from the gut mucosa in response to food ingestion. Specific receptors for melatonin have been detected in many gastrointestinal tissues including the pancreas. Melatonin as well as its precursor, L-tryptophan, attenuates the severity of acute pancreatitis and protects the pancreatic tissue from the damage caused by acute inflammation. The beneficial effect of melatonin on acute pancreatitis, which has been reported in many experimental studies and supported by clinical observations, is related to: (1) enhancement of antioxidant defense of the pancreatic tissue, through direct scavenging of toxic radical oxygen (ROS) and nitrogen (RNS) species, (2) preservation of the activity of antioxidant enzymes; such as superoxide dismutase (SOD), catalase (CAT), or glutathione peroxidase (GPx), (3) the decline of pro-inflammatory cytokine tumor necrosis α (TNFα) production, accompanied by stimulation of an anti-inflammatory IL-10, (4) improvement of pancreatic blood flow and decrease of neutrophil infiltration, (5) reduction of apoptosis and necrosis in the inflamed pancreatic tissue, (6) increased production of chaperon protein (HSP60), and (7) promotion of regenerative process in the pancreas. Conclusion. Endogenous melatonin produced from L-tryptophan could be one of the native mechanisms protecting the pancreas from acute damage and accelerating regeneration of this gland. The beneficial effects of melatonin shown in experimental studies suggest that melatonin ought to be employed in the clinical trials as a supportive therapy in acute pancreatitis and could be used in people at high risk for acute pancreatitis to prevent the development of pancreatic inflammation.

Antioxidant therapy in acute pancreatitis: experimental and clinical evidence

SIGNIFICANCE

Oxidative stress plays an important role in the pathogenesis of both acute and chronic pancreatitis. Although its impact is well investigated and has been studied clinically in chronic pancreatitis, it is less well defined for acute pancreatitis.

RECENT ADVANCES

Pathophysiological aspects of oxidative stress in acute pancreatitis have shown that reactive oxidative species (ROS) participate in the inflammatory cascade, and mediate inflammatory cell adhesion and consecutive tissue damage. Furthermore, ROS are involved in the generation of pain as another important clinical feature of patients suffering from acute pancreatitis.

CRITICAL ISSUES

Despite sufficient basic and experimental knowledge and evidence, the step from bench to bedside has not been successfully performed. Only a limited number of clinical studies are available that can give convincing evidence for the use of antioxidants in the clinical setting of acute pancreatitis.

FUTURE DIRECTIONS

Future studies are required to evaluate potential benefits of antioxidative substances to attenuate the severity of acute pancreatitis. Special focus should be put on the aspect of pain generation and the progression from mild to severe acute pancreatitis in the clinical setting.

Calcium and reactive oxygen species in acute pancreatitis: friend or foe?

SIGNIFICANCE

Acute pancreatitis (AP) is a debilitating and, at times, lethal inflammatory disease, the causes and progression of which are incompletely understood. Disruption of Ca(2+) homeostasis in response to precipitants of AP leads to loss of mitochondrial integrity and cellular necrosis.

RECENT ADVANCES

While oxidative stress has been implicated as a major player in the pathogenesis of this disease, its precise roles remain to be defined. Recent developments are challenging the perception of reactive oxygen species (ROS) as nonspecific cytotoxic agents, suggesting that ROS promote apoptosis that may play a vital protective role in cellular stress since necrosis is avoided.

CRITICAL ISSUES

Fresh clinical findings have indicated that antioxidant treatment does not ameliorate AP and may actually worsen the outcome. This review explores the complex links between cellular Ca(2+) signaling and the intracellular redox environment, with particular relevance to AP.

FUTURE DIRECTIONS

Recent publications have underlined the importance of both Ca(2+) and ROS within the pathogenesis of AP, particularly in the determination of cell fate. Future research should elucidate the subtle interplay between Ca(2+) and redox mechanisms that operate to modulate mitochondrial function, with a view to devising strategies for the preservation of organellar function.

Protective effects of lycopene on cerulein-induced experimental acute pancreatitis in rats

BACKGROUND

The purpose of our study was to evaluate the protective effect of the strong antioxidant and anti-inflammatory agent, lycopene, on oxidative stress in a rat model of cerulein-induced acute edematous pancreatitis.

METHODS

Sprague-Dawley rats were pretreated with lycopene (50 mg/kg, i.p.) or saline 15 min before cerulein was given 20 μg/kg (i.p.) at 1-h intervals within 4 h. Twelve hours after cerulein or saline injections, the animals were killed by decapitation. Blood samples were collected to analyze amylase, lipase, and proinflammatory cytokines (TNF-α and IL-1ß). Pancreatic tissues were taken for the determination of tissue glutathione (GSH) and malondialdehyde (MDA) levels, Na(+)/K(+)-ATPase, and myeloperoxidase (MPO) activities. Tissue samples were also examined histologically.

RESULTS

Acute pancreatitis caused significant decrease in tissue GSH levels and Na(+)/K(+)-ATPase activity, while pancreatic MDA levels and MPO activity were increased. Furthermore, TNF-α, IL-1ß, and amylase lipase levels were also significantly increased. On the other hand, lycopene pretreatment reserved all these biochemical indices as well as histopathologic alterations that were induced by cerulein.

CONCLUSIONS

According to the results, lycopene protects the pancreatic tissues from oxidative damage induced by cerulein, and this effect possibly involves the inhibition of neutrophil infiltration and lipid peroxidation. These results suggest that high dietary intake of tomatoes may have protective effects against acute pancreatitis.

New paradigms in chronic intestinal inflammation and colon cancer: role of melatonin

In intestinal bowel disease (IBD), immune-mediated conditions exert their effects through various cells and proinflammatory mediators. Recent data support a participation of the endoplasmic reticulum stress and mitochondrial dysfunctions in IBD. Moreover, it is evident that chronic degenerative pathologies, including IBD, share comparable disease mechanisms with alteration in the autophagy mechanisms. Chronic inflammation in IBD exposes these patients to a number of signals known to have tumorigenic effects. This circuitry of inflammation and cancer modifies apoptosis and autophagy, and promotes cellular cycle progression, invasion, and angiogenesis. Melatonin has been shown as a specific antioxidant reducing oxidative damage in both lipid and aqueous cell environments. However, several studies provide further insight into the molecular mechanisms of melatonin action in the colon. In this line, recent data suggest that melatonin modulates autophagy and sirtuin activity. An anti-autophagic property of melatonin has been demonstrated, and it could contribute to its anti-oncogenic activity. Nevertheless, there is no information about whether antitumoral effects of melatonin on colon cancer are dependent on autophagy. Sirtuins have pleiotropic effects on cancer development, being reported both as facilitator and as suppressor of colon cancer development. Sirtuins and melatonin are connected through the circadian clock machinery, and melatonin seems able to correct the alterations in sirtuin activity associated with several pathological conditions. Autophagy and sirtuin activities are linked through 5'AMP-activated protein kinase (AMPK) activation, which switches on autophagy and increases sirtuin. The effect of melatonin on AMPK and the impact of this effect on IBD and colon cancer remain an open question.

Protective role of endogenous melatonin in the early course of human acute pancreatitis

Melatonin plays a protective role in experimental acute pancreatitis (AP) because of its antioxidative, antiinflammatory, and immunomodulatory effects. This study presents the first data on the dynamic changes of endogenous melatonin in the early phase of human AP. Morning (08:00 hr) serum melatonin concentrations were measured by ELISA in 75 patients with AP for the first 5 days after the onset of pain. According to the Atlanta classification, 26 patients suffered a mild AP (MAP). The other 49 developed a severe AP (SAP). Median melatonin concentrations of healthy volunteers were used as a control. Median melatonin level in healthy controls was 18.5 pg/mL. Levels of melatonin were significantly higher in the first 24 hr after onset of disease in patients with MAP compared to those with SAP, 51.2 versus 8.7 pg/mL (P = 0.01). Melatonin values were the same in MAP and SAP during the remainder of the study period. Melatonin concentrations during the first 24 hr after the onset of pain in younger patients (<35 yrs old) were significantly higher than levels in older patients (>35 yrs): 73 versus 8.7 pg/mL (P = 0.01). No correlation existed between melatonin levels and the following parameters: gender, etiology (biliary versus alcohol induced), and histological findings (edematous versus necrotizing versus infected necrosis). High endogenous melatonin serum levels in the first 24 hr after the onset of AP played a protective role and favoured a mild course of the disease in humans, especially in young patients.

Melatonin modulates the severity of taurocholate-induced acute pancreatitis in the rat

The aim of this study was to investigate the effects of melatonin on serum amylase, tumor necrosis factor-alpha (TNF-alpha) and histological changes in rats with taurocholate-induced acute pancreatitis. Thirty male Wistar rats were randomly divided into three groups; group 1, group 2 and group 3 were enrolled as melatonin, control and sham groups, respectively (n = 10 per group). Acute pancreatitis was induced by 1 ml/kg body weight using 5% taurocholate injection into the biliopancreatic duct in groups 1 and 2 after clamping the hepatic duct. Those in group 1 received 50 mg/kg body weight melatonin by intraperitoneal (i.p.) injection. Group 2 received physiological saline i.p. at the same dose. Group 3 solely underwent laparotomy with cannulation of the biliopancreatic duct. Twenty-four hours after the intervention, the rats were killed, and serum samples were collected to measure amylase and TNF-alpha levels. Simultaneously, pancreatic tissues were removed, stained with hematoxylin-eosin and examined under a light microscope. Serum amylase and TNF-alpha levels were significantly lower in the melatonin group compared to the controls (P < 0.001). The total histological score, including edema, inflammation, perivascular infiltrate, acinar necrosis, fat necrosis and hemorrhage, was also significantly lower in the melatonin group as compared to the control (P < 0.0001). In conclusion, melatonin is potentially capable of reducing pancreatic damage by decreasing serum TNF-alpha levels in taurocholate-induced acute pancreatitis in rats. This result supports the idea that melatonin might be beneficial in ameliorating the severity of acute pancreatitis.

The selective inhibition of type IV phosphodiesterase attenuates the severity of the acute pancreatitis in rats

Phosphodiesterases (PDEs) are enzymes primarily responsible for regulation of the intracellular cyclic nucleotides. Among these enzymes, the type 4 PDE is highly expressed in most immune and inflammatory cells and its inhibition causes the suppression of immune and inflammatory cell activity, including production of cytokines. This study was designed to investigate the efficacy of the type 4 PDE inhibitor rolipram on acute pancreatitis in rats. Rats were divided into three groups--treatment, control, and sham. In the treatment and control groups, rats were pretreated with rolipram and vehicle before acute pancreatitis was induced. The pretreatment of rats with rolipram significantly reduced the amylase (P<0.0001) and IL-1β levels (P=0.002) compared to vehicle treated rats. Also, mean histopathological scores were significantly reduced by rolipram treatment (P<0.005). It can be concluded that rolipram ameliorates severity of pancreatitis in rats.

The ultrastructural and biochemical evidences of the beneficial effects of chronic caffeic acid phenethyl ester and melatonin administration on brain and cerebellum of aged rats

Nervous system is highly vulnerable to the deleterious effects of age-related oxidative stress. A large body of researches has consistently confirmed the implication of free radicals both in normal cerebral ageing and ageing-related pathologies. In the present study, in addition to the light and electron microscopic pictures of brain and cerebellum of young, old and antioxidant administered old Sprague-Dawley rats, pro-oxidant status was evaluated in terms of measurements of total glutathione, lipid peroxidation (malondialdehyde) and activities of superoxide dismutase, catalase and glutathione peroxidase. Taking the results together, we suggest that supplemental administration of caffeic acid phenethyl ester and melatonin is beneficial in delaying age-related cellular damage in nervous system.

Melatonin modulates the severity of taurocholate-induced acute pancreatitis in the rat

The aim of this study was to investigate the effects of melatonin on serum amylase, tumor necrosis factor-alpha (TNF-alpha) and histological changes in rats with taurocholate-induced acute pancreatitis. Thirty male Wistar rats were randomly divided into three groups; group 1, group 2 and group 3 were enrolled as melatonin, control and sham groups, respectively (n = 10 per group). Acute pancreatitis was induced by 1 ml/kg body weight using 5% taurocholate injection into the biliopancreatic duct in groups 1 and 2 after clamping the hepatic duct. Those in group 1 received 50 mg/kg body weight melatonin by intraperitoneal (i.p.) injection. Group 2 received physiological saline i.p. at the same dose. Group 3 solely underwent laparotomy with cannulation of the biliopancreatic duct. Twenty-four hours after the intervention, the rats were killed, and serum samples were collected to measure amylase and TNF-alpha levels. Simultaneously, pancreatic tissues were removed, stained with hematoxylin-eosin and examined under a light microscope. Serum amylase and TNF-alpha levels were significantly lower in the melatonin group compared to the controls (P < 0.001). The total histological score, including edema, inflammation, perivascular infiltrate, acinar necrosis, fat necrosis and hemorrhage, was also significantly lower in the melatonin group as compared to the control (P < 0.0001). In conclusion, melatonin is potentially capable of reducing pancreatic damage by decreasing serum TNF-alpha levels in taurocholate-induced acute pancreatitis in rats. This result supports the idea that melatonin might be beneficial in ameliorating the severity of acute pancreatitis.

Ischemic conditioning by short periods of reperfusion attenuates renal ischemia/reperfusion induced apoptosis and autophagy in the rat

Prolonged ischemia amplified iscehemia/reperfusion (IR) induced renal apoptosis and autophagy. We hypothesize that ischemic conditioning (IC) by a briefly intermittent reperfusion during a prolonged ischemic phase may ameliorate IR induced renal dysfunction. We evaluated the antioxidant/oxidant mechanism, autophagy and apoptosis in the uninephrectomized Wistar rats subjected to sham control, 4 stages of 15-min IC (I15 x 4), 2 stages of 30-min IC (I30 x 2), and total 60-min ischema (I60) in the kidney followed by 4 or 24 hours of reperfusion. By use of ATP assay, monitoring O2-. amounts, autophagy and apoptosis analysis of rat kidneys, I60 followed by 4 hours of reperfusion decreased renal ATP and enhanced reactive oxygen species (ROS) level and proapoptotic and autophagic mechanisms, including enhanced Bax/Bcl-2 ratio, cytochrome C release, active caspase 3, poly-(ADP-ribose)-polymerase (PARP) degradation fragments, microtubule-associated protein light chain 3 (LC3) and Beclin-1 expression and subsequently tubular apoptosis and autophagy associated with elevated blood urea nitrogen and creatinine level. I30 x 2, not I15 x 4 decreased ROS production and cytochrome C release, increased Manganese superoxide dismutase (MnSOD), Copper-Zn superoxide dismutase (CuZnSOD) and catalase expression and provided a more efficient protection than I60 against IR induced tubular apoptosis and autophagy and blood urea nitrogen and creatinine level. We conclude that 60-min renal ischemia enhanced renal tubular oxidative stress, proapoptosis and autophagy in the rat kidneys. Two stages of 30-min ischemia with 3-min reperfusion significantly preserved renal ATP content, increased antioxidant defense mechanisms and decreased ischemia/reperfusion enhanced renal tubular oxidative stress, cytosolic cytochrome C release, proapoptosis and autophagy in rat kidneys.

Role of oxidative stress in pancreatic inflammation

Reactive oxygen and reactive nitrogen species (ROS/RNS) have been implicated in the pathogenesis of acute and chronic pancreatitis. Clinical and basic science studies have indicated that ROS/RNS formation processes are intimately linked to the development of the inflammatory disorders. The detrimental effects of highly reactive ROS/RNS are mediated by their direct actions on biomolecules (lipids, proteins, and nucleic acids) and activation of proinflammatory signal cascades, which subsequently lead to activation of immune responses. The present article summarizes the possible sources of ROS/RNS formation and the detailed signaling cascades implicated in the pathogenesis of pancreatic inflammation, as observed in acute and chronic pancreatitis. A therapeutic ROS/RNS-scavenging strategy has been advocated for decades; however, clinical studies examining such approaches have been inconsistent in their results. Emerging evidence indicates that pancreatitis-inducing ROS/RNS generation may be attenuated by targeting ROS/RNS-generating enzymes and upstream mediators.

Pancreatic exocrine insufficiency in LXRbeta-/- mice is associated with a reduction in aquaporin-1 expression

Liver X receptors (LXRs) alpha and beta are nuclear oxysterol receptors with a key role in cholesterol, triglyceride, and glucose metabolism. In LXRbeta(-/-) mice on a normal diet, there is a reduction in size of perigonadal fat pad and, on high-fat diet there is resistance to obesity. In the present study, we investigated the reason for the resistance of LXRbeta(-/-) mice to weight gain. In LXRbeta(-/-) mice we found pancreatic exocrine insufficiency with reduced serum levels of amylase and lipase, reduced proteolytic activity in feces, chronic inflammatory infiltration, and, in the ductal epithelium, an increased apoptosis without compensatory proliferation. Electron microscopy revealed ductal dilatation with intraductal laminar structures characteristic of cystic fibrosis. To investigate the relationship between LXRbeta and pancreatic secretion, we studied the expression of LXRbeta and the water channel, aquaporin-1 (AQP1), in the ductal epithelium of the pancreas. In WT mice, ductal epithelial cells expressed LXRbeta in the nuclei and AQP1 on the plasma membrane. In LXRbeta(-/-) mice neither LXRbeta nor AQP1 was detectable. Moreover, in WT mice the LXR agonist (T2320) increased AQP1 gene expression. These data demonstrate that in LXRbeta(-/-) mice dietary resistance to weight gain is caused by pancreatic insufficiency and that LXRbeta regulates pancreatic exocrine secretion through the control of AQP1 expression. Pancreatic exocrine insufficiency is the main cause of malabsorption syndrome responsible for weight loss in adults and growth failure in children. Several genes are known to be involved in the pathogenesis and susceptibility to pancreatic insufficiency. LXRbeta should be included in that list.

The contradictory effects of nitric oxide in caerulein-induced acute pancreatitis in rats

This study was planned to observe the effects of nitric oxide synthesis on the antioxidative defense enzymes and pancreatic tissue histology in caerulein-induced acute pancreatitis. Acute pancreatitis was induced by intraperitoneal injections of 50 microg/kg caerulein, L-arginine used for NO induction and N(omega)-nitro-L-arginine methyl ester (L-NAME) used for NO inhibition. In the caerulein group acinar cell degeneration, interstitial inflammation, oedema and haemorrhage were detected. Pancreatic damage scores were decreased with both NO induction and inhibition (p<0.05). MDA, GSH-Px, CAT, GSH and SOD activities were significantly changed in the caerulein group and indicated increased oxidative stress. Both NO induction and inhibition decreased this oxidative stress. It is concluded that both nitric oxide induction and inhibition ameliorated caerulein-induced acute pancreatitis. The findings indicate that a certain amount of NO production has beneficial effects in experimental acute pancreatitis, but uncontrolled over-production of NO may be detrimental.

Comparative effects of several therapatic agents on hepatic damage induced by acute experimental pancreatitis

PURPOSE

The prognosis of acute pancreatitis (AP) depends upon the degree of pancreatic necrosis and the intensity of multisystem organ failure. The liver contributes to the systemic manifestations of AP by releasing some cytokines. This study was undertaken to examine comparative effects of melatonin, antioxidant mixture containing L(+)-ascorbic acid and N-acetyl cysteine, pentoxifylline and L-arginine on hepatic damage induced by caerulein-pancreatitis.

RESULTS

The liver specimens of all groups showed histopathological alterations such as hepatocyte necrosis, intracellular vacuolization, vascular congestion, sinusoidal dilatation and inflammatory infiltration. TEM studies revealed vacuole formation, mitochondrial degeneration, lysosome accumulation and necrosis. The mean histopathological score of the caerulein group was significantly different from that of each treatment group.

CONCLUSION

L-Arginine and antioxidant administration be important for reducing hepatic damage induced by AP. Improvement of hepatic damage, in turn, might be beneficial for the prognosis of AP.

Relationship between acute pancreatitis and oxidative stress

Under the imbalance between generation of reactive oxygen species and inadequate antioxidant defense systems, oxidative stress can cause cell damage either directly or indirectly through altering signaling pathways. It is the etiopathogenisis and also the consequence of many diseases. Oxidative injury plays an important role not only in the pathogenesis of acute pancreatitis (AP) but also in pancreatitis-induced damages of other organs such as heart, liver, lung, kidney, alimentary canal and so on. Oxidative stress can produce a higher level of reactive oxygen species (ROS) and reactive nitrogen species (RNS), which induce inflammatory reaction and microcirculation disturbance, and cell necrosis or apoptosis, leading to pancreatic inflammation and multiple organ dysfunction syndromes. The antioxidants can decrease the production of oxygen free radicals (or directly scavenge them), protect the antioxidant enzyme activity, reinforce the antioxidative capacity of bodies, and consequently play an obvious therapeutic effect on AP.

Melatonin modulates acid/base transport in human pancreatic carcinoma cells

Melatonin was found to improve pancreatic organ function in diseased animals. To study whether pancreatic bicarbonate secretion is stimulated by melatonin, investigations were done in two human ductal pancreatic adenocarcinoma cell lines MIA PaCa-2 (MIA) and PANC-1 (PANC). Using the fluorescence pH-sensor BCECF-AM, we monitored melatonin effects on basal intracellular pH (pH(i)), and on pH(i) recovery after intracellular alkalinization produced by the removal of extracellular HCO(3) (-)/CO(2). Exposure to 1 microM melatonin for 24 hrs and presence of the indoleamine during the experiment increases the basal pH(i). Moreover, pHi recovery and HCO(3) (-) secretion are facilitated after the alkaline load. These findings are in line with the observed increase in mRNA expression of the Na(+)/HCO(3) (-)-cotransporter SLC4A4b for the uptake and the Cl(-)/HCO(3) (-)-exchanger SLC26A6 for the secretion of HCO(3) (-). The reduction in Na(+)/H(+)- exchanger SLC9A1 mRNA would favor pH(i) recovery after alkalinization, but it does not explain the initial increase in pHi. This controversial effect and the requirement for continuous presence of melatonin throughout the experiment suggest that nontranscriptional signalling may contribute to the effects of melatonin on acid/base movements. In summary, we show a stimulatory effect of melatonin on bicarbonate secretion in the pancreatic cancer cell lines which may help to prevent duodenal damage.