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

Acute pancreatitis: pathogenesis and emerging therapies

Acute pancreatitis is a severe inflammatory disorder with limited treatment options. Improved understanding of disease mechanisms has led to new and potential therapies. Here we summarize what we view as some of the most promising new therapies for treating acute pancreatitis, emphasizing the rationale of specific treatments based on disease mechanisms. Targeted pharmacologic interventions are highlighted. We explore potential treatment benefits and risks concerning reducing acute injury, minimizing complications, and improving long-term outcomes. Mechanisms associated with acute pancreatitis initiation, perpetuation, and reconstitution are highlighted, along with potential therapeutic targets and how these relate to new treatments.

Associations between Melatonin, Neuroinflammation, and Brain Alterations in Depression

Pro-inflammatory systemic conditions that can cause neuroinflammation and subsequent alterations in brain regions involved in emotional regulation have been suggested as an underlying mechanism for the pathophysiology of major depressive disorder (MDD). A prominent feature of MDD is disruption of circadian rhythms, of which melatonin is considered a key moderator, and alterations in the melatonin system have been implicated in MDD. Melatonin is involved in immune system regulation and has been shown to possess anti-inflammatory properties in inflammatory conditions, through both immunological and non-immunological actions. Melatonin has been suggested as a highly cytoprotective and neuroprotective substance and shown to stimulate all stages of neuroplasticity in animal models. The ability of melatonin to suppress inflammatory responses through immunological and non-immunological actions, thus influencing neuroinflammation and neurotoxicity, along with subsequent alterations in brain regions that are implicated in depression, can be demonstrated by the antidepressant-like effects of melatonin. Further studies that investigate the associations between melatonin, immune markers, and alterations in the brain structure and function in patients with depression could identify potential MDD biomarkers.

Molecular links between endocrine, nervous and immune system during chronic stress

INTRODUCTION

The stress response is different in various individuals, however, the mechanisms that could explain these distinct effects are not well known and the molecular correlates have been considered one at the time. Particular harmful conditions occur if the subject, instead to cope the stressful events, succumb to them, in this case, a cascade reaction happens that through different signaling causes a specific reaction named "sickness behaviour." The aim of this article is to review the complex relations among important molecules belonging to Central nervous system (CNS), immune system (IS), and endocrine system (ES) during the chronic stress response.

METHODS

After having verified the state of art concerning the function of cortisol, norepinephrine (NE), interleukin (IL)-1β and melatonin, we describe as they work together.

RESULTS

We propose a speculative hypothesis concerning the complex interplay of these signaling molecules during chronic stress, highlighting the role of IL-1β as main biomarker of this effects, indeed, during chronic stress its increment transforms this inflammatory signal into a nervous signal (NE), in turn, this uses the ES (melatonin and cortisol) to counterbalance again IL-1β. During cortisol resistance, a vicious loop occurs that increments all mediators, unbalancing IS, ES, and CNS networks. This IL-1β increase would occur above all when the individual succumbs to stressful events, showing the Sickness Behaviour Symptoms. IL-1β might, through melatonin and vice versa, determine sleep disorders too.

CONCLUSION

The molecular links here outlined could explain how stress plays a role in etiopathogenesis of several diseases through this complex interplay.

Melatonin treatment of pigs with acute pancreatitis reduces inflammatory reaction of pancreatic tissue and enhances fitness score of pigs: experimental research

Background

Severe acute pancreatitis is associated with high morbidity and mortality. Melatonin is known as the activator of antioxidant enzymes. The main purpose of this study was to evaluate the clinical effect of melatonin treatment in a pig model with induced acute pancreatitis.

Methods

In this study, acute pancreatitis was induced in 38 German domestic pigs (German Hybrid). After induction of acute pancreatitis, 18 animals were treated with melatonin. Intraoperative clinical data, postoperative blood parameters, fitness, and Porcine Well-being (PWB) score, and post-mortal histopathological data were analyzed in both study groups.

Results

The matching procedure created two groups (melatonin group and control group) which were very similar. The fitness and PWB score were postoperative significantly enhanced in the melatonin group as compared to the control group (p = 0.005 and p = 0.003). Additionally, histological analysis revealed that acinar necrosis, fat tissue necrosis, and edema were significantly reduced in the melatonin group as compared to the non-melatonin group (p = 0.025, p = 0.003, and p = 0.028).

Conclusions

Pigs, which were treated with melatonin, were characterized by higher fitness and PWB scores than those of the control group. Moreover, melatonin treatment reduces the acinar necrosis, fat tissue necrosis, and edema of pancreatic tissue. Thus, melatonin might be a useful therapeutic option in severe acute pancreatitis.

Dim light at night: physiological effects and ecological consequences for infectious disease

Light pollution has emerged as a pervasive component of land development over the past century. Several detrimental impacts of this anthropogenic influence have been identified in night shift workers, laboratory rodents, and a plethora of wildlife species. Circadian, or daily, patterns are interrupted by the presence of light at night and have the capacity to alter rhythmic physiological or behavioral characteristics. Indeed, biorhythm disruption can lead to metabolic, reproductive, and immunological dysfunction depending on the intensity, timing, duration, and wavelength of light exposure. Light pollution, in many forms and by many pathways, is thus apt to affect the nature of host-pathogen interactions. However, no research has yet investigated this possibility. The goal of this manuscript is to outline how dim light at night, a relevant and common form of light pollution, may affect disease dynamics by interrupting circadian rhythms and regulation of immune responses as well as opportunities for host-parasite interactions and subsequent transmission risk including spillover into humans. We close by proposing some promising interventions including alternative lighting methods or vector control efforts.

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.

Calendula officinalis ameliorates l-arginine-induced acute necrotizing pancreatitis in rats

CONTEXT

Calendula officinalis L. (Asteraceae) has been traditionally used in treating inflammation of internal organs, gastrointestinal tract ulcers and wound healing.

OBJECTIVE

The present study investigates the effect of ethanol extract (95%) of Calendula officinalis flowers in l-arginine induced acute necrotizing pancreatitis in rats.

MATERIALS AND METHODS

Rats were divided into four groups: normal control, l-arginine control, Calendula officinalis extract (COE) treated and melatonin treated (positive control), which were further divided into subgroups (24 h, day 3 and 14) according to time points. Two injections of l-arginine 2 g/kg i.p. at 1 h intervals were administered in l-arginine control, COE and melatonin-treated groups to produce acute necrotizing pancreatitis. Biochemical parameters [serum amylase, lipase, pancreatic amylase, nucleic acid content, total proteins, transforming growth factor-β1 (TGF-β1), collagen content, lipid peroxidation, reduced glutathione and nitrite/nitrate] and histopathological studies were carried out.

RESULTS

COE treatment (400 mg/kg p.o.) was found to be beneficial. This was evidenced by significantly lowered histopathological scores (2 at day 14). Nucleic acid content (DNA 21.1 and RNA 5.44 mg/g pancreas), total proteins (0.66 mg/mL pancreas) and pancreatic amylase (1031.3 100 SU/g pancreas) were significantly improved. Marked reduction in pancreatic oxidative and nitrosative stress; collagen (122 μmoles/100 mg pancreas) and TGF-β1 (118.56 pg/mL) levels were noted. Results obtained were comparable to those of positive control.

DISCUSSION AND CONCLUSION

The beneficial effect of COE may be attributed to its antioxidant, antinitrosative and antifibrotic actions. Hence, the study concludes that COE promotes spontaneous repair and regeneration of the pancreas.

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.

Endoplasmic reticulum stress is activated in acute pancreatitis

Endoplasmic reticulum (ER) is one of the most important cell organelles in the body, regulating protein synthesis, folding and aggregation. Endoplasmic reticulum stress (ERS) is a particular subcellular pathological process involving an imbalance of homeostasis and ER disorder. In the early stage of ERS, cells show a protective unfolded protein response that changes the cellular transcriptional and translational programs to alleviate the process. Therefore, a certain degree of ERS can activate the protective adaptation of cells, whereas sustained severe ERS triggers an apoptotic signal and leads to apoptosis. Acute pancreatitis is a disease caused by trypsin digestion of the pancreas, although the pathogenesis is not completely understood. However, a close association has been suggested between pancreatitis and ERS. This article reviewed relevant research advances and discussed the effect of ERS on the development and progression of acute pancreatitis.

Melatonin induces the expression of Nrf2-regulated antioxidant enzymes via PKC and Ca2+ influx activation in mouse pancreatic acinar cells

The goal of this study was to evaluate the potential activation of the nuclear factor erythroid 2-related factor and the antioxidant-responsive element (Nrf2-ARE) signaling pathway in response to melatonin in isolated mouse pancreatic acinar cells. Changes in intracellular free Ca(2+) concentration were followed by fluorimetric analysis of fura-2-loaded cells. The activations of PKC and JNK were measured by Western blot analysis. Quantitative reverse transcription-polymerase chain reaction was employed to detect the expression of Nrf2-regulated antioxidant enzymes. Immunocytochemistry was employed to determine nuclear location of phosphorylated Nrf2, and the cellular redox state was monitored following MitoSOX Red-derived fluorescence. Our results show that stimulation of fura-2-loaded cells with melatonin (1 µM to 1 mM), in the presence of Ca(2+) in the extracellular medium, induced a slow and progressive increase of [Ca(2+)](c) toward a stable level. Melatonin did not inhibit the typical Ca(2+) response induced by CCK-8 (1 nM). When the cells were challenged with indoleamine in the absence of Ca(2+) in the extracellular solution (medium containing 0.5 mM EGTA) or in the presence of 1 mM LaCl(3), to inhibit Ca(2+) entry, we could not detect any change in [Ca(2+)](c). Nevertheless, CCK-8 (1 nM) was able to induce the typical mobilization of Ca(2+). When the cells were incubated with the PKC activator PMA (1 µM) in the presence of Ca(2+) in the extracellular medium, we observed a response similar to that noted when the cells were challenged with melatonin 100 µM. However, in the presence of Ro31-8220 (3 µM), a PKC inhibitor, stimulation of cells with melatonin failed to evoke changes in [Ca(2+)]c. Immunoblots, using an antibody specific for phospho-PKC, revealed that melatonin induces PKCα activation, either in the presence or in the absence of external Ca(2+). Melatonin induced the phosphorylation and nuclear translocation of the transcription factor Nrf2, and evoked a concentration-dependent increase in the expression of the antioxidant enzymes NAD(P)H-quinone oxidoreductase 1, catalytic subunit of glutamate-cysteine ligase, and heme oxygenase-1. Incubation of MitoSOX Red-loaded pancreatic acinar cells in the presence of 1 nM CCK-8 induced a statistically significant increase in dye-derived fluorescence, reflecting an increase in oxidation, that was abolished by pretreatment of cells with melatonin (100 µM) or PMA (1 µM). On the contrary, pretreatment with Ro31-8220 (3 µM) blocked the effect of melatonin on CCK-8-induced increase in oxidation. Finally, phosphorylation of JNK in the presence of CCK-8 or melatonin was also observed. We conclude that melatonin, via modulation of PKC and Ca(2+) signaling, could potentially stimulate the Nrf2-mediated antioxidant response in mouse pancreatic acinar cells.

Laboratory markers predicting severity of acute pancreatitis

Acute pancreatitis (AP) is an inflammatory disease of highly variable severity, ranging from mild cases with low mortality to severe cases with high mortality. Numerous biomarkers have been studied as potential early predictors of the severity of this disease so that treatment can be optimally tailored to prevent complications. We aim to present and discuss the most relevant biomarkers for early severity assessment in AP that have been studied to date. We review the current literature on biomarkers that have been used to predict the severity in AP. C-reactive protein (CRP) is still considered to be the gold standard, with a cut-off value of 150 mg/ml 48 h after disease onset. Other markers, including procalcitonin (PCT) and interleukin 6 (IL-6) have been implemented in some hospitals, but are not used on a routine basis. Most other markers, including acute phase proteins (LBP, SAA, PTX3), cytokines (Il-8, TNF-a, MIF), activation peptides of pancreatic proteases (TAP, CAPAP, PLAP), antiproteases (AAT, a2M), adhesion molecules (ICAM-1, selectins, E-cadherin) and leukocyte-derived enzymes (PA2, PMN-E) have shown some promising results but have not been routinely implemented. Furthermore, new and interesting biomarkers (Copeptin, TRX-1, Ang-2, E-2) have shown good results, but more research is needed to determine if they could play a role in the future. Various reasons why new markers for disease severity have not been adopted in daily routine include low accuracy, cumbersome laboratory techniques and high cost. Despite these difficulties, research is still very active in finding new markers to predict the severity of AP.

Pharmacological dose of melatonin reduces cytosolic calcium load in response to cholecystokinin in mouse pancreatic acinar cells

Intracellular Ca(2+) overload has been considered a common pathological precursor of pancreatic injury. In this study, the effects of melatonin on Ca(2+) mobilization induced by cholecystokinin octapeptide (CCK-8) in freshly isolated mouse pancreatic acinar cells have been examined. Changes in intracellular free Ca(2+) concentration were followed by single cell fluorimetry. For this purpose, cells were loaded with the Ca(2+)-sensitive fluorescent dye fura-2-acetoxymethyl ester. In order to evaluate the contribution of Ca(2+) transport at the plasma membrane, at the endoplasmic reticulum (ER) or at the mitochondria, cells were incubated with CCK-8 alone or in combination with LaCl3, thapsigargin (Tps), or FCCP to, respectively, uncouple Ca(2+) transport at these localizations. The experiments were performed in the absence or in the presence of melatonin in combination with the stimuli mentioned. Our results show that the total Ca(2+) mobilization evoked by CCK-8 was attenuated by a 30% in the presence of 100 µM melatonin compared with the responses induced by CCK-8 alone. Upon inhibition of Ca(2+) transport into the ER by Tps, Ca(2+) mobilization was also reduced in the presence of melatonin. In the presence of LaCl3 plus melatonin, the total Ca(2+) mobilization induced by CCK-8 was significantly decreased, compared with the response obtained without melatonin but in the presence of LaCl3. No major differences were found when the cells were incubated with CCK-8 or Tps alone or in combination with LaCl3 plus melatonin and FCCP, compared with the responses obtained in the absence of FCCP. The initial Ca(2+) release from intracellular stores evoked by CCK-8 or Tps was not significantly reduced in the presence of melatonin. The effect of melatonin could be explained on the basis of a stimulated Ca(2+) transport out of the cell through the plasma membrane and by a stimulation of Ca(2+) reuptake into the ER. Accumulation of Ca(2+) into mitochondria might not be a major mechanism stimulated by melatonin. We conclude that melatonin alleviates intracellular Ca(2+) accumulation, a situation potentially leading to cell damage in the exocrine pancreas.

Melatonin reduces bacterial translocation by preventing damage to the intestinal mucosa in an experimental severe acute pancreatitis rat model

Recent studies have demonstrated that melatonin significantly decreased all studied acute pancreatitis-associated inflammatory parameters, in addition to reducing apoptosis and necrosis associated with pancreatic injury. However, the effect of melatonin on gut barrier dysfunction and bacterial translocation has not been fully elucidated. This study aimed to investigate the protective effects of melatonin on intestinal integrity in a rat model of severe acute pancreatitis (SAP) to evaluate whether melatonin prevented intestine barrier dysfunction and reduced bacterial translocation. Forty male Sprague Dawley (SD) rats were randomly divided into three groups, with 8 rats in the sham operation (SO) group, 18 rats in the SAP group and 14 SAP rats in the melatonin treatment (MT) group. SAP was induced by retrograde injection of 4% taurocholate into the biliopancreatic duct. Melatonin was administered 30 min prior to taurocholate injection in the melatonin-treated rats. All rats were sacrificed 24 h subsequent to pancreatitis induction. Real-time fluorescence quantitative polymerase chain reaction was used to detect and quantify Escherichia coli (E. coli) O157 in postcava blood. The microvilli structure was also analyzed with transmission electron microscopy. The level of E. coli DNA in the MT group was significantly lower than in rats in the SAP group. No E. coli DNA was detected in the control group. Villus height and crypt depth in the ileum were significantly higher in the MT and control groups compared to the SAP group, and were significantly higher in the MT group than in the SAP group. These results suggested that melatonin prevented gut barrier dysfunction and reduced bacterial translocation, resulting in reduced pancreatic-associated infections and decreased early mortality rates.

Neuronostatin ameliorates sodium taurocholate-induced acute pancreatitis in rats

BACKGROUND AND AIMS

Neuronostatin is encoded in the preprosomatostatin gene and exerts important physiological actions on neuronal and cardiovascular regulation and metabolism in diverse tissues. An intraperitoneal injection of neuronostatin can induce c-Jun expression in the periphery of pancreatic islets. Because of the relatively high amount of neuronostatin present in the pancreas, it is necessary to investigate the effects of neuronostatin on pancreas. Furthermore, little is known about the effect of neuronostatin on acute pancreatitis.

METHODS

Neuronostatin (30, 60, and 120 nmol) was injected in to the external jugular vein 30 min before retrograde infusion of 2 % sodium taurocholate into the pancreaticobiliary duct. After 6 h, histological damage of the pancreas was evaluated by pancreas weight and paraffin section. A blood sample was collected to determine the serum amylase and lipase activities.

RESULTS

In our findings, neuronostatin groups had a reduction in interstitial edema, acinar cell vacuolization, and inflammatory infiltration of the pancreas compared with the model group. Biochemical data showed that serum amylase and lipase activities were significantly decreased in neuronostatin-pretreated groups by comparison with the model group.

CONCLUSIONS

Histopathologic examination suggests that neuronostatin ameliorated the histological damage of sodium taurocholate-induced acute pancreatitis in rats. The biochemical analysis was consistent with that obtained from histopathologic examination, which was toward a trend of attenuating acute pancreatitis. In summary, neuronostatin might be potentially capable of ameliorating pancreatic damage in acute pancreatitis in rats.

Rosiglitazone attenuates the severity of hyperlipidemic severe acute pancreatitis in rats

Peroxisome proliferator-activated receptor-γ (PPAR-γ) ligand regulates adipocyte differentiation and insulin sensitivity, and exerts antihyperlipidemic and anti-inflammatory effects. However, the mechanisms by which PPAR-γ ligands affect hyperlipidemia with severe acute pancreatitis (SAP) have not been fully elucidated. The present study investigated the effects of rosiglitazone, a PPAR-γ ligand, on hyperlipidemia with SAP in a rat model. The hyperlipidemia was induced with a high-fat diet and SAP was induced by the administration of sodium taurocholate (TCA). The hyperlipidemia was shown to aggravate the severity of the sodium taurocholate-induced SAP. However, rosiglitazone demonstrated significant antihyperlipidemic and anti-inflammatory effects in the rats with high-lipid diet-induced hyperlipidemia and SAP.

Melatonin modulates Ca2+ mobilization and amylase release in response to cholecystokinin octapeptide in mouse pancreatic acinar cells

In the present work, we have evaluated the effect of an acute addition of melatonin on cholecystokinin octapeptide (CCK-8)-evoked Ca(2+) signals and amylase secretion in mouse pancreatic acinar cells. For this purpose, freshly isolated mouse pancreatic acinar cells were loaded with fura-2 to study intracellular free Ca(2+) concentration ([Ca(2+)](c)). Amylase release and cell viability were studied employing colorimetric methods. Our results show that CCK-8 evoked a biphasic effect on amylase secretion, finding a maximum at a concentration of 0.1 nM and a reduction of secretion at higher concentrations. Pre-incubation of cells with melatonin (1 μM-1 mM) significantly attenuated enzyme secretion in response to high concentrations of CCK-8. Stimulation of cells with 1 nM CCK-8 led to a transient increase in [Ca(2+)](c), followed by a decrease towards a constant level. In the presence of 1 mM melatonin, stimulation of cells with CCK-8 resulted in a smaller [Ca(2+)](c) peak response, a faster rate of decay of [Ca(2+)](c) and lower values for the steady state of [Ca(2+)](c), compared with the effect of CCK-8 alone. Melatonin also reduced the oscillatory pattern of Ca(2+) mobilization evoked by a physiological concentration of CCK-8 (20 pM), and completely inhibited Ca(2+) mobilization induced by 10 pM CCK-8. On the other hand, Ca(2+) entry from the extracellular space was not affected in the presence of melatonin. Finally, melatonin alone did not change cell viability. We conclude that melatonin, at concentrations higher than those found in blood, might regulate exocrine pancreatic function via modulation of Ca(2+) signals.

Clinical significance of melatonin concentrations in predicting the severity of acute pancreatitis

AIM: To assess the value of plasma melatonin in predicting acute pancreatitis when combined with the acute physiology and chronic health evaluation II (APACHEII) and bedside index for severity in acute pancreatitis (BISAP) scoring systems.

METHODS: APACHEII and BISAP scores were calculated for 55 patients with acute physiology (AP) in the first 24 h of admission to the hospital. Additionally, morning (6:00 AM) serum melatonin concentrations were measured on the first day after admission. According to the diagnosis and treatment guidelines for acute pancreatitis in China, 42 patients suffered mild AP (MAP). The other 13 patients developed severe AP (SAP). A total of 45 healthy volunteers were used in this study as controls. The ability of melatonin and the APACHEII and BISAP scoring systems to predict SAP was evaluated using a receiver operating characteristic (ROC) curve. The optimal melatonin cutoff concentration for SAP patients, based on the ROC curve, was used to classify the patients into either a high concentration group (34 cases) or a low concentration group (21 cases). Differences in the incidence of high scores, according to the APACHEII and BISAP scoring systems, were compared between the two groups.

RESULTS: The MAP patients had increased melatonin levels compared to the SAP (38.34 ng/L vs 26.77 ng/L) (P = 0.021) and control patients (38.34 ng/L vs 30.73 ng/L) (P = 0.003). There was no significant difference inmelatoninconcentrations between the SAP group and the control group. The accuracy of determining SAP based on the melatonin level, the APACHEII score and the BISAP score was 0.758, 0.872, and 0.906, respectively, according to the ROC curve. A melatonin concentration ≤ 28.74 ng/L was associated with an increased risk of developing SAP. The incidence of high scores (≥ 3) using the BISAP system was significantly higher in patients with low melatonin concentration (≤ 28.74 ng/L) compared to patients with high melatonin concentration (> 28.74 ng/L) (42.9% vs 14.7%, P = 0.02). The incidence of high APACHEII scores (≥ 10) between the two groups was not significantly different.

CONCLUSION: The melatonin concentration is closely related to the severity of AP and the BISAP score. Therefore, we can evaluate the severity of disease by measuring the levels of serum melatonin.

Melatonin: buffering the immune system

Melatonin modulates a wide range of physiological functions with pleiotropic effects on the immune system. Despite the large number of reports implicating melatonin as an immunomodulatory compound, it still remains unclear how melatonin regulates immunity. While some authors argue that melatonin is an immunostimulant, many studies have also described anti-inflammatory properties. The data reviewed in this paper support the idea of melatonin as an immune buffer, acting as a stimulant under basal or immunosuppressive conditions or as an anti-inflammatory compound in the presence of exacerbated immune responses, such as acute inflammation. The clinical relevance of the multiple functions of melatonin under different immune conditions, such as infection, autoimmunity, vaccination and immunosenescence, is also reviewed.

The protective effects of taurine on experimental acute pancreatitis in a rat model

The aim of this study was to investigate the protective effects of taurine (Tau) on experimental acute pancreatitis (AP) in a rat model by measuring cytokines and oxidant stress markers.

Forty rats were randomly divided into four groups: sham, AP, Tau and AP + Tau. AP was induced with sodium taurocholate. No treatment was given to the AP. All rats were killed 5 days later. Pancreatic tissues of rats and blood samples were obtained.

Tau treatment significantly decreased serum amylase activity ( p < 0.001), total injury score ( p < 0.001), malondialdehyde levels ( p < 0.001) and myeloperoxidase (MPO) activity ( p < 0.001). There was no significant difference between the Tau and AP + Tau groups in serum and pancreatic tumor necrosis factor-α, interleukin (IL)-1β and IL-6 levels ( p = 1.000). Histopathologic scores in the AP + Tau and Tau groups were significantly lower compared with the AP group (both p < 0.001).

These results showed that Tau reduces lipid peroxidation, amylase and MPO activities and the concentrations of proinflammatory cytokines secondary to AP and also increases superoxide dismutase and glutathione peroxidase activities in rats with sodium taurocholate-induced AP. It also has a marked ameliorative effect at histopathologic lesions. With these effects, Tau protects the cells from oxidative damage, reduces inflammation and promotes regression of pancreatic damage.

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.

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.

Melatonin ameliorates acute necrotizing pancreatitis by the regulation of cytosolic Ca2+ homeostasis

OBJECTIVES

This study aims to investigate the relationship between the protective effects of melatonin in pancreas and the expression of sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) and Na(+)/Ca(2+) exchanger (NCX) in rats with acute necrotizing pancreatitis (ANP), to verify whether melatonin ameliorates ANP by alleviating calcium overload.

METHODS

Ninety-six male Sprague-Dawley rats were randomly divided into four groups (sham operation group, ANP group, melatonin treatment group, melatonin contrast group). ANP was induced by the retrograde injection of 4% taurocholate (1 ml/kg body weight) into the biliopancreatic duct. Melatonin (50 mg/kg body weight) was administered 30 min before the induction of ANP in the melatonin treatment group. Rats in each group were euthanized at 1, 4, and 8 h after ANP induction. Pancreatic tissues were removed to measure SERCA and NCX levels and cytosolic calcium ion (Ca(2+)) concentration ([Ca(2+)](i)).

RESULTS

At each time point, SERCA and NCX levels in the melatonin treatment group were significantly higher than that in the ANP group, and lower than that in the sham group and the melatonin contrast group. These levels did not differ between the 4- and 8-h time points in the ANP group. [Ca(2+)](i) in pancreatic acinar cells was higher in the melatonin treatment group than in the sham group and the melatonin contrast group, but lower than in the ANP group, at each time point.

CONCLUSION

Melatonin can reduce pancreatic damage via the up-regulation of SERCA and NCX expression, which can alleviate calcium overload in pancreatic acinar cells.

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.