Downregulation of matrix metalloproteinase-9 by melatonin during prevention of alcohol-induced liver injury in mice

Significance of Melatonin in the Regulation of Circadian Rhythms and Disease Management

Melatonin, the 'hormone of darkness' is a neuronal hormone secreted by the pineal gland and other extra pineal sites. Responsible for the circadian rhythm and seasonal behaviour of vertebrates and mammals, melatonin is responsible for regulating various physiological conditions and the maintenance of sleep, body weight and the neuronal activities of the ocular sites. With its unique amphiphilic structure, melatonin can cross the cellular barriers and elucidate its activities in the subcellular components, including mitochondria. Melatonin is a potential scavenger of oxygen and nitrogen-reactive species and can directly obliterate the ROS and RNS by a receptor-independent mechanism. It can also regulate the pro- and anti-inflammatory cytokines in various pathological conditions and exhibit therapeutic activities against neurodegenerative, psychiatric disorders and cancer. Melatonin is also found to show its effects on major organs, particularly the brain, liver and heart, and also imparts a role in the modulation of the immune system. Thus, melatonin is a multifaceted candidate with immense therapeutic potential and is still considered an effective supplement on various therapies. This is primarily due to rectification of aberrant circadian rhythm by improvement of sleep quality associated with risk development of neurodegenerative, cognitive, cardiovascular and other metabolic disorders, thereby enhancing the quality of life.

Melatonin Prevents Alcohol- and Metabolic Dysfunction- Associated Steatotic Liver Disease by Mitigating Gut Dysbiosis, Intestinal Barrier Dysfunction, and Endotoxemia

Melatonin (MT) has often been used to support good sleep quality, especially during the COVID-19 pandemic, as many have suffered from stress-related disrupted sleep patterns. It is less known that MT is an antioxidant, anti-inflammatory compound, and modulator of gut barrier dysfunction, which plays a significant role in many disease states. Furthermore, MT is produced at 400-500 times greater concentrations in intestinal enterochromaffin cells, supporting the role of MT in maintaining the functions of the intestines and gut-organ axes. Given this information, the focus of this article is to review the functions of MT and the molecular mechanisms by which it prevents alcohol-associated liver disease (ALD) and metabolic dysfunction-associated steatotic liver disease (MASLD), including its metabolism and interactions with mitochondria to exert its antioxidant and anti-inflammatory activities in the gut-liver axis. We detail various mechanisms by which MT acts as an antioxidant, anti-inflammatory compound, and modulator of intestinal barrier function to prevent the progression of ALD and MASLD via the gut-liver axis, with a focus on how these conditions are modeled in animal studies. Using the mechanisms of MT prevention and animal studies described, we suggest behavioral modifications and several exogenous sources of MT, including food and supplements. Further clinical research should be performed to develop the field of MT in preventing the progression of liver diseases via the gut-liver axis, so we mention a few considerations regarding MT supplementation in the context of clinical trials in order to advance this field of research.

Melatonin loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles reduce inflammation, inhibit apoptosis and protect rat's liver from the hazardous effects of CCL4

Liver is an important organ that carries out major important functions including the detoxification of harmful chemicals. Numerous studies have lately focused on the impact of various substances, such as chemical pollutants and pharmaceutical drugs, on the liver. Melatonin (Mel) has been reported for the protection against liver injury. In order to enhance Mel therapeutic benefits and prevent any potential negative effects, Mel has to be delivered to the injured liver. Therefore, the goal of the current investigation was to create Mel-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (Mel-PLGA NPs) to alleviate carbon tetrachloride (CCL4)-induced liver damage in male Sprague Dawley rats. The prepared Mel-PLGA NPs were physically characterized to determine its size and charge. Moreover, Mel-PLGA NPs were examined, in vitro, to determine its antioxidant, anticoagulant, anti-inflammatory and cytotoxicity effects before being used in vivo. The effect of NPs on liver injury was evaluated through biochemical, immunological, histopathological examination and flow cytometry technique. Mel-PLGA NPs were smooth and spherical with no signs of aggregation and have in vitro antioxidant, anti-inflammatory and anticoagulant effects. NPs varied in size from 87 to 96 nm in transmission electron microscope images, while their hydrodynamic diameter was 41 nm and their zeta potential was -6 mV. Mel-PLGA NPs had encapsulation efficiency (EE%) and drug loading (DL%) of 59.9 and 12.5%, respectively. Treatment with Mel-PLGA NPs ameliorated all histopathological changes, in liver sections, that resulted from CCL4 administration; where, liver sections of treated groups were similar to those of healthy control GI. NPs administration were superior to free Mel and reversed the elevated levels of liver function enzymes, inflammatory cytokines and matrix metalloproteinases to their normal levels. Moreover, liver sections of groups treated with NPs showed negative immunostaining for nuclear factor-κB (NF-κB) and C-reactive protein indicating their anti-inflammatory behavior. Mel-PLGA NPs significantly protected liver from the toxicity of CCL4. The effective dose of NPs was 5 mg/kg indicating a reduction in the required Mel dose and its associated adverse effects.

Newly Synthesized 3-Indolyl Furanoid Inhibits Matrix Metalloproteinase-9 Activity and Prevents Nonsteroidal Anti-inflammatory Drug-Induced Gastric Ulceration

Indomethacin, a known nonsteroidal anti-inflammatory drug (NSAID) induces gastric inflammation, causing degradation of the extracellular matrix by specific matrix metalloproteinases (MMPs). We investigated the antiulcer efficacy of 3-indolyl furanoids (3g and 3c, i.e., methoxy substitution at 4- and 5-positions of the indole ring, respectively), derived from indomethacin. Interestingly, 3g protected against indomethacin-induced gastropathy in vivo by inhibiting MMP-9. Our work established a chemical modification strategy for the development of safer NSAIDs. Moreover, in vitro and in silico studies confirmed that 3g inhibited MMP-9 activity with an IC₅₀ value of 50 μM by binding to the catalytic cleft of MMP-9, leading to ulcer prevention. Pharmacokinetics was presented as the mean concentration-time profile in the rat plasma, and the extraction efficiency was greater than 70%, showing a C_max of 104.48 μg/mL after 6.0 h (t_max) treatment with half-life and area under the curve being 7.0 h and 1273.8 h μg/mL, respectively, indicating the higher antiulcer potency of 3g.

Melatonin: A novel candidate for the treatment of osteoarthritis

Osteoarthritis (OA), characterized by cartilage erosion, synovium inflammation, and subchondral bone remodeling, is a common joint degenerative disease worldwide. OA pathogenesis is regulated by multiple predisposing factors, including imbalanced matrix metabolism, aberrant inflammatory response, and excessive oxidative stress. Moreover, melatonin has been implicated in development of several degenerative disorders owing to its potent biological functions. With regards to OA, melatonin reportedly promotes synthesis of cartilage matrix, inhibition of chondrocyte apoptosis, attenuation of inflammatory response, and suppression of matrix degradation by regulating the TGF-β, MAPK, or NF-κB signaling pathways. Notably, melatonin has been associated with amelioration of oxidative damage by restoring the OA-impaired intracellular antioxidant defense system in articular cartilage. Findings from preliminary application of melatonin or melatonin-loaded biomaterials in animal models have affirmed its potential anti-arthritic effects. Herein, we summarize the anti-arthritic effects of melatonin on OA cartilage and demonstrate that melatonin has potential therapeutic efficacy in treating OA.

Omeprazole prevents stress induced gastric ulcer by direct inhibition of MMP-2/TIMP-3 interactions

The healing of damaged tissues in gastric tract starts with the extracellular matrix (ECM) remodeling by the action of matrix metalloproteinases (MMPs). Particularly, MMP-2 (gelatinase-A) maintains ECM structure and function by degrading type IV collagen, the major component of basement membranes and by clearing denatured collagen. The proteolytic activities of MMPs are critically balanced by endogenous tissue inhibitors of metalloproteinases (TIMPs) and disruption of this balance results in several diseases. The well-known drug omeprazole is a proton pump inhibitor used for curing gastric ulcer. However, the action of omeprazole in ECM remodeling on gastroprotection has never been explored. Herein, using rat model of gastric ulcer, we report that restraint cold stress caused increase apoptosis to surface epithelia of gastric tissues along with TIMP-3 upregulation and inhibition of MMP-2 activity thereon. In contrast, omeprazole treatment suppressed TIMP-3 while increasing MMP-2 activity and thereby, restoring MMP-2/TIMP-3 balance. Additionally, nanomolar binding constant (K_d = 318 nM) of omeprazole with purified MMP-2 indicates a direct effect of omeprazole in restoring MMP-2 activity. Further in silico simulations revealed a plausible mechanism of action of omeprazole for TIMP-3 deactivation. Altogether, omeprazole restores MMP-2 activity and reduces apoptosis while preventing acute stress-induced gastric ulcer that occurs via suppression of nuclear factor kappa B (NF-κB) activity and peroxisome proliferator-activated receptor gamma activity (PPAR-γ). This represents an unprecedented correlation between physical docking of drug molecule to a protease and the severity of organ injury and provides a novel therapeutic approach to prevent stress induced tissue damage.

Exogenous Melatonin Alleviates Skeletal Muscle Wasting by Regulating Hypothalamic Neuropeptides Expression in Endotoxemia Rats

To investigate whether exogenous melatonin (MLT) could alleviate skeletal muscle wasting by regulating hypothalamic neuropeptides expression. Adult male Sprague Dawley rats were intraperitoneally injected with lipopolysaccharide (LPS) (10 mg/kg), followed by MLT (30 mg/kg/day) or saline for 3 days. Hypothalamic tissues and skeletal muscle were obtained on day 3. Skeletal muscle wasting was measured by the mRNA expression of two E3 ubiquitin ligases, muscle atrophy F-box and muscle ring finger 1 as well as 3-methylhistidine (3-MH) and tyrosine release. Three hypothalamic neuropeptides (POMC, AgRP, CART) expression were detected in all groups. POMC expression knockdown was achieved by ARC injection of lentiviruses containing shRNA against POMC. Two weeks after ARC viruses injection, rats were i.p. injected with LPS (10 mg/kg) followed by MLT (30 mg/kg/day) or saline for 3 days. Brain tissues were harvested for immunostaining. In septic rats, 3-MH, tyrosine release and muscle atrophic gene expression were significantly decreased in MLT treated group. POMC and CART expression were lower while AgRP expression was higher in MLT treated group. Furthermore, in septic rats treated with MLT, muscle wasting in those with lower expression of neuropeptide POMC did not differ from those with normal POMC expression. Exogenous MLT could alleviate skeletal muscle wasting in septic rats by regulating hypothalamic neuropeptides.

Melatonin-primed ADMSCs elicit an efficacious therapeutic response in improving high-fat diet induced non-alcoholic fatty liver disease in C57BL/6J mice

Background

Stem cells are widely used for therapy including treatment of liver damage. Adipose-derived mesenchymal stem cells (ADMSCs) administered to treat fatty liver are known to improve liver function but their use is restricted due to a poor success rate. This study investigates efficacy of melatonin-primed ADMSCs (Mel. MSCs) in experimentally induced non-alcoholic fatty liver disease (NAFLD).

Results

MSCs treated with LPS showed prominent DCFDA fluorescence as compared to the untreated cells. Also, the JC-1 staining had accounted for higher intensity of green monomer and a weak fluorescence of red dimer indicating weaker mitochondrial membrane potential. But melatonin co-treatment could make necessary corrective changes as evidenced by reverse set of results. The overall cell survival was also found to be improved following melatonin treatment as evidenced by the MTT assay. Also, the antioxidant (Nrf2 and Ho-1) and anti-inflammatory genes (Il-4 and Il-10) showed a decrement in their mRNA levels following LPS treatment whereas the pro-inflammatory genes (Tnf-α, Il-6, Tlr-4, and Lbp) showed a reciprocal increment in the said group. Melatonin co-treatment accounted for an improved status of antioxidant and anti-inflammatory genes as evidenced by their mRNA levels. High-fat high-fructose diet (HFFD) fed C57BL/6J mice recorded higher serum AST and ALT levels and fatty manifestation in histology of liver along with lowered mRNA levels of antioxidant (Nrf2, Catalase, and Gss) genes and Hgf. These set of parameters showed a significant improvement in HFFD + Mel.MSC group.

Conclusion

A significant improvement in viability of MSCs was recorded due to lowered intracellular oxidative stress and improves mitochondrial membrane potential. Further, melatonin-primed MSCs accounted for a significant decrement in fatty manifestations in liver and an improved physiological status of NAFLD in HFFD fed C57BL/6J mice. Taken together, it is hypothesized that melatonin priming to MSCs prior to its use can significantly augment the success of stem cell therapy.

Protective Mechanism of Edible Food Plants against Alcoholic Liver Disease with Special Mention to Polyphenolic Compounds

Alcoholic liver disease (ALD) is one type of liver disease, causing a global healthcare problem and mortality. The liver undergoes tissue damage by chronic alcohol consumption because it is the main site for metabolism of ethanol. Chronic alcohol exposure progresses from alcoholic fatty liver (AFL) to alcoholic steatohepatitis (ASH), which further lead to fibrosis, cirrhosis, and even hepatocellular cancer. Therapeutic interventions to combat ALD are very limited such as use of corticosteroids. However, these therapeutic drugs are not effective for long-term usage. Therefore, additional effective and safe therapies to cope with ALD are urgently needed. Previous studies confirmed that edible food plants and their bioactive compounds exert a protective effect against ALD. In this review article, we summarized the hepatoprotective potential of edible food plants and their bioactive compounds. The underlying mechanism for the prevention of ALD by edible food plants was as follows: anti-oxidation, anti-inflammation, lipid regulation, inhibition of apoptosis, gut microbiota composition modulation, and anti-fibrosis.

The structural characteristics, antioxidant and hepatoprotection activities of polysaccharides from Chimonanthus nitens Oliv. leaves

This work aimed to investigate the structural characteristics, antioxidant activities and hepatoprotection effect of Chimonanthus nitens Oliv. leaves polysaccharides (COP) on alcohol-induced oxidative damage in mice. Physical and chemical analysis showed that COP contained four monosaccharides including arabinose (Ara), mannose (Man), glucose (Glu) and galactose (Gal), with mass percentages of 26.6%, 5.1%, 32.2% and 36.0%, respectively, which was a heteropolysaccharide with both α- and β- configurations. In vivo experiments indicated that oral administration COP significantly reduced the levels of ALT, AST and MDA in serum, and significantly increased the activity of SOD and GSH-Px. Mice pretreated with COP had a higher superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity in liver and lower content of TNF-α, IL-6 and IL-1β in the liver and serum when compared with alcohol exposure. In addition, the liver histopathological changes induced by alcohol returned to normal in the COP pretreatment group. These results suggest that COP has a protective effect on acute liver injury induced by alcohol.

Advances in Characterizing Recently-Identified Molecular Actions of Melatonin: Clinical Implications

Melatonin, N-acetyl-5-methoxy-tryptamine, was discovered to be a product of serotonin metabolism in the mammalian pineal gland where its synthesis is under control of the light:dark cycle. Besides its regulatory pathway involving ganglion cells in the retina, the neural connections between the eyes and the pineal gland include the master circadian clock, the suprachiasmatic nuclei, and the central and peripheral nervous systems. Since pineal melatonin is released into the blood and into the cerebrospinal fluid, it has access to every cell in an organism and it mediates system-wide effects. Subsequently, melatonin was found in several extrapineal organs and, more recently, perhaps in every cell of every organ. In contrast to the pinealocytes, non-pineal cells do not discharge melatonin into the blood; rather it is used locally in an intracrine, autocrine, or paracrine manner. Melatonin levels in non-pineal cells do not exhibit a circadian rhythm and do not depend on circulating melatonin concentrations although when animals are treated with exogenous melatonin it is taken up by presumably all cells. Mitochondria are the presumed site of melatonin synthesis in all cells; the enzymatic machinery for melatonin synthesis has been identified in mitochondria. The association of melatonin with mitochondria, because of its ability to inhibit oxidative stress, is very fortuitous since these organelles are a major site of damaging reactive oxygen species generation. In this review, some of the actions of non-pineal-derived melatonin are discussed in terms of cellular and subcellular physiology.

Possible application of melatonin treatment in human diseases of the biliary tract

Melatonin was discovered in 1958 by Aaron Lerner. Its name comes from the ability of melatonin to change the shape of amphibian melanophores from stellate to roundish. Starting from the 1980s, the role of melatonin in the regulation of mammalian circadian and seasonal clocks has been elucidated. Presently, several other effects have been identified in different organs. For example, the beneficial effects of melatonin in models of liver damage have been described. This review gives first a general background on experimental and clinical data on the use of melatonin in liver damage. The second part of the review focuses on the findings related to the role of melatonin in biliary functions, suggesting a possible use of melatonin therapy in human diseases of the biliary tree.

Biological effects of melatonin on human adipose‑derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are capable of differentiating into other cell types and exhibit immunomodulatory effects. MSCs are affected by several intrinsic and extrinsic signaling modulators, including growth factors, cytokines, extracellular matrix and hormones. Melatonin, produced by the pineal gland, is a hormone that regulates sleep cycles. Recent studies have shown that melatonin improves the therapeutic effects of stem cells. The present study aimed to investigate whether melatonin enhances the biological activities of human adipose-derived MSCs. The results demonstrated that treatment with melatonin promoted cell proliferation by inducing SRY-box transcription factor 2 gene expression and preventing replicative senescence. In addition, melatonin exerted anti-adipogenic effects on MSCs. PCR analysis revealed that the expression of the CCAAT enhancer binding protein a gene, a key transcription factor in adipogenesis, was decreased following melatonin treatment, resulting in reduced adipogenic differentiation in an in vitro assay. The present study also examined the effect of melatonin on the immunomodulatory response using a co-culture system of human peripheral blood mononuclear cells and MSCs. Activated T cells were strongly inhibited following melatonin exposure compared with those in the control group. Finally, the favorable effects of melatonin on MSCs were confirmed using luzindole, a selective melatonin receptor antagonist. The proliferation-promoting, anti-inflammatory effects of melatonin suggested that melatonin-treated MSCs may be used for effective cell therapy.

Protective role of melatonin in early-stage and end-stage liver cirrhosis

The liver is composed of hepatocytes, cholangiocytes, Kupffer cells, sinusoidal endothelial cells, hepatic stellate cells (HSCs) and dendritic cells; all these functional and interstitial cells contribute to the synthesis and secretion functions of liver tissue. However, various hepatotoxic factors including infection, chemicals, high‐fat diet consumption, surgical procedures and genetic mutations, as well as biliary tract diseases such as sclerosing cholangitis and bile duct ligation, ultimately progress into liver cirrhosis after activation of fibrogenesis. Melatonin (MT), a special hormone isolated from the pineal gland, participates in regulating multiple physiological functions including sleep promotion, circadian rhythms and neuroendocrine processes. Current evidence shows that MT protects against liver injury by inhibiting oxidation, inflammation, HSC proliferation and hepatocyte apoptosis, thereby inhibiting the progression of liver cirrhosis. In this review, we summarize the circadian rhythm of liver cirrhosis and its potential mechanisms as well as the therapeutic effects of MT on liver cirrhosis and earlier‐stage liver diseases including liver steatosis, nonalcoholic fatty liver disease and liver fibrosis. Given that MT is an antioxidative and anti‐inflammatory agent that is effective in eliminating liver injury, it is a potential agent with which to reverse liver cirrhosis in its early stage.

Efficacy of Ozone and Selenium Therapy for Alcoholic Liver Injury: An Experimental Model

BACKGROUND/AIM

Alcoholic liver disease is an important health problem which is reversible during early stages of liver damage, but becomes permanent with time. Nowadays, many studies focus on various agents that prevent, reduce or slow the progression of the toxic effects of alcohol. In our study, we investigated the efficiency of ozone and selenium against oxidative damage in a model of alcohol-induced liver damage.

MATERIALS AND METHODS

Forty-eight female Wistar Albino rats between 4 and 6 months of age and weighing 190-250 g were included in the study and were used as models of alcohol liver damage. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), serum and tissue total oxidant levels, serum and tissue total antioxidant levels, and the histopathological evaluation of the liver were performed in 8 groups.

RESULTS

In the statistical analysis, it was observed that ozone and/or selenium therapies decreased the AST levels. Total oxidant and antioxidant serum levels were found to vary in serum and tissue. Ozone and/or selenium therapies decreased liver damage, according to histopathological findings.

CONCLUSION

Through ozone and/or selenium therapies, less damage was observed histopathologically compared to the alcohol group. It is thought that the results of our study can be used in individual treatments following confirmation of liver damage in alcoholic patients.

The multiple protective roles and molecular mechanisms of melatonin and its precursor N-acetylserotonin in targeting brain injury and liver damage and in maintaining bone health

Melatonin is a neurohormone associated with sleep and wakefulness and is mainly produced by the pineal gland. Numerous physiological functions of melatonin have been demonstrated including anti-inflammation, suppressing neoplastic growth, circadian and endocrine rhythm regulation, and its potent antioxidant activity as well as its role in regeneration of various tissues including the nervous system, liver, bone, kidney, bladder, skin, and muscle, among others. In this review, we summarize the recent advances related to the multiple protective roles of melatonin receptor agonists, melatonin and N-acetylserotonin (NAS), in brain injury, liver damage, and bone health. Brain injury, including traumatic brain injury, ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, and newborn perinatal hypoxia-ischemia encephalopathy, is a major cause of mortality and disability. Liver disease causes serious public health problems and various factors including alcohol, chemical pollutants, and drugs induce hepatic damage. Osteoporosis is the most common bone disease in humans. Due in part to an aging population, both the cost of care of fracture patients and the annual fracture rate have increased steadily. Despite the discrepancy in the pathophysiological processes of these disorders, time frames and severity, they may share several common molecular mechanisms. Oxidative stress is considered to be a critical factor in these pathogeneses. We update the current state of knowledge related to the molecular processes, mainly including anti-oxidative stress, anti-apoptosis, autophagy dysfunction, and anti-inflammation as well as other properties of melatonin and NAS. Particularly, the abilities of melatonin and NAS to directly scavenge oxygen-centered radicals and toxic reactive oxygen species, and indirectly act through antioxidant enzymes are disscussed. In this review, we summarize the similarities and differences in the protection provided by melatonin and/or NAS in brain, liver and bone damage. We analyze the involvement of melatonin receptor 1A (MT1), melatonin receptor 1B (MT2), and melatonin receptor 1C (MT3) in the protection of melatonin and/or NAS. Additionally, we evaluate their potential clinical applications. The multiple mechanisms of action and multiple organ-targeted properties of melatonin and NAS may contribute to development of promising therapies for clinical trials.

Melatonin in regulation of inflammatory pathways in rheumatoid arthritis and osteoarthritis: involvement of circadian clock genes

Rheumatoid arthritis (RA) and osteoarthritis (OA) are the two most prevalent joint diseases. A such, they are important causes of pain and disability in a substantial proportion of the human population. A common characteristic of these diseases is the erosion of articular cartilage and consequently joint dysfunction. Melatonin has been proposed as a link between circadian rhythms and joint diseases including RA and OA. This hormone exerts a diversity of regulatory actions through binding to specific receptors and intracellular targets as well as having receptor-independent actions as a free radical scavenger. Cytoprotective effects of melatonin involve a myriad of prominent receptor-mediated pathways/molecules associated with inflammation, of which the role of omnipresent NF-κB signalling is crucial. Likewise, disturbance of circadian timekeeping is closely involved in the aetiology of inflammatory arthritis. Melatonin is shown to stimulate cartilage destruction/regeneration through direct/indirect modulation of the expression of the main circadian clock genes, such as BMAL, CRY and/or DEC2. In the current article, we review the effects of melatonin on RA and OA, focusing on its ability to regulate inflammatory pathways and circadian rhythms. We also review the possible protective effects of melatonin on RA and OA pathogenesis. LINKED ARTICLES: This article is part of a themed section on Recent Developments in Research of Melatonin and its Potential Therapeutic Applications. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.16/issuetoc.

Capsaicin, the pungent principle of peppers, ameliorates alcohol-induced acute liver injury in mice via modulation of matrix metalloproteinases

Alcohol, the most common cause for hepatic injury, may further deteriorate the hepatic tissue when left unattended. Capsaicin, the pungent principle of chilli peppers, possesses antioxidant and anti-inflammatory properties and is a proven dietary antioxidant in various ailments. However, its role in alcohol-induced hepatic injury is unclear. In this study, we investigated the effects of capsaicin on the hepatic tissue of mice treated with alcohol. Acute liver injury was induced in mice by oral gavage of 5 doses of 10 mL/kg of 50% ethyl alcohol at an interval of 12 h. The tissue antioxidant levels along with the mitochondrial functional parameters and matrix metalloproteinase levels were evaluated in the hepatic tissues of mice following alcohol challenge. The results showed that alcohol intake significantly attenuated the hepatic antioxidant levels and mitochondrial function. These changes were accompanied by enhanced serum hepatic injury markers and matrix metalloproteinases. However, capsaicin treatment (10 and 20 mg/kg, oral) throughout the experimental period caused a drastic improvement in the hepatic tissue of the alcohol-treated mice, reflected by the normalization of hepatic enzyme and protein levels along with restored histological alterations. These results indicate that capsaicin, as a dietary intervention, may prevent alcohol-induced acute liver injury.

Effects of Sleep Quality on Melatonin Levels and Inflammatory Response after Major Abdominal Surgery in an Intensive Care Unit

Disruption of nocturnal sleep in an intensive care unit may remarkably affect production of melatonin, which is also known to have anti-inflammatory properties. In the present study, we aimed to investigate the effect of sleep quality on melatonin levels and inflammation after surgery. Thus, we compared the patients, who were screened in the side-rooms where the lights were dimmed and noise levels were reduced, with the patients who received usual care. Preoperative and postoperative urine 6-sulphatoxymelatonin, serum interleukin-1 (IL-1), interleukin-6 (IL-6), and c-reactive protein (CRP) levels were measured and data on sleep quality was collected using the Richards–Campbell Sleep Questionnaire. Postoperative CRP and IL-6 levels were greater in the control group than in the experimental group, whereas postoperative 24 h melatonin levels were greater than preoperative levels and the difference was steeper in the experimental group in concordance with sleep quality scores. Thus, the regulation of light and noise in ICUs may help the recovery after major surgeries in patients, potentially by increasing melatonin production, which has anti-inflammatory properties.

Exposure to Concentrated Ambient Fine Particulate Matter Induces Vascular Endothelial Dysfunction via miR-21

Vascular endothelial permeability transition does not cause significant lesions, but enhanced permeability may contribute to the development of vascular and other diseases, including atherosclerosis, hypertension, heart failure and cancer. Therefore, elucidating the effect of Particulate Matter 2.5 (PM_2.5) on vascular endothelial permeability could help prevent disease that might be caused by PM_2.5. Our previous study and the present one revealed that PM_2.5 significantly increased the permeability of vascular endothelial cells and disrupted the barrier function of the vascular endothelium in Sprague Dawley (SD) rats. We found that the effect occurred mainly through induction of signal transducer and activator of transcription 3 (STAT3) phosphorylation, further transcriptional regulation of microRNA21 (miR-21) and promotion of miR-21 expression. These changes post-transcriptionally repress tissue inhibitor of metalloproteinases 3 (TIMP3) and promote matrix metalloproteinases 9 (MMP9) expression. This work provides evidence that PM_2.5 exerts direct inhibitory action on vascular endothelial barrier function and might give rise to a number of vascular diseases.

Effects of Melatonin on Liver Injuries and Diseases

Liver injuries and diseases are serious health problems worldwide. Various factors, such as chemical pollutants, drugs, and alcohol, could induce liver injuries. Liver diseases involve a wide range of liver pathologies, including hepatic steatosis, fatty liver, hepatitis, fibrosis, cirrhosis, and hepatocarcinoma. Despite all the studies performed up to now, therapy choices for liver injuries and diseases are very few. Therefore, the search for a new treatment that could safely and effectively block or reverse liver injuries and diseases remains a priority. Melatonin is a well-known natural antioxidant, and has many bioactivities. There are numerous studies investigating the effects of melatonin on liver injuries and diseases, and melatonin could regulate various molecular pathways, such as inflammation, proliferation, apoptosis, metastasis, and autophagy in different pathophysiological situations. Melatonin could be used for preventing and treating liver injuries and diseases. Herein, we conduct a review summarizing the potential roles of melatonin in liver injuries and diseases, paying special attention to the mechanisms of action.

A hot water extract of turmeric (Curcuma longa) suppresses acute ethanol-induced liver injury in mice by inhibiting hepatic oxidative stress and inflammatory cytokine production

Turmeric (Curcuma longa) is a widely used spice that has various biological effects, and aqueous extracts of turmeric exhibit potent antioxidant activity and anti-inflammatory activity. Bisacurone, a component of turmeric extract, is known to have similar effects. Oxidative stress and inflammatory cytokines play an important role in ethanol-induced liver injury. This study was performed to evaluate the influence of a hot water extract of C. longa (WEC) or bisacurone on acute ethanol-induced liver injury. C57BL/6 mice were orally administered WEC (20 mg/kg body weight; BW) or bisacurone (60 µg/kg BW) at 30 min before a single dose of ethanol was given by oral administration (3·0 g/kg BW). Plasma levels of aspartate aminotransferase and alanine aminotransferase were markedly increased in ethanol-treated mice, while the increase of these enzymes was significantly suppressed by prior administration of WEC. The increase of alanine aminotransferase was also significantly suppressed by pretreatment with bisacurone. Compared with control mice, animals given WEC had higher hepatic tissue levels of superoxide dismutase and glutathione, as well as lower hepatic tissue levels of thiobarbituric acid-reactive substances, TNF-α protein and IL-6 mRNA. These results suggest that oral administration of WEC may have a protective effect against ethanol-induced liver injury by suppressing hepatic oxidation and inflammation, at least partly through the effects of bisacurone.

Melatonin role preventing steatohepatitis and improving liver transplantation results

Liver steatosis is a prevalent process that is induced due to alcoholic or non-alcoholic intake. During the course of these diseases, the generation of reactive oxygen species, followed by molecular damage to lipids, protein and DMA occurs generating organ cell death. Transplantation is the last-resort treatment for the end stage of both acute and chronic hepatic diseases, but its success depends on ability to control ischemia-reperfusion injury, preservation fluids used, and graft quality. Melatonin is a powerful endogenous antioxidant produced by the pineal gland and a variety of other because of its efficacy in organs; melatonin has been investigated to improve the outcome of organ transplantation by reducing ischemia-reperfusion injury and due to its synergic effect with organ preservation fluids. Moreover, this indolamine also prevent liver steatosis. That is important because this disease may evolve leading to an organ transplantation. This review summarizes the observations related to melatonin beneficial actions in organ transplantation and ischemic-reperfusion models.

Effects of melatonin on HIF-1α and VEGF expression and on the invasive properties of hepatocarcinoma cells

Liver cancer is the sixth most commonly occurring cancer globally, and the main histological type is hepatocellular carcinoma. This type of neoplasia has a poor prognosis due to a high rate of recurrence and intrahepatic metastasis, which are closely are closely associated with the angiogenic process. Vascular endothelial growth factor (VEGF), which is under the control of hypoxia inducible factor-1α (HIF-1α), stimulates the proliferation of endothelial cells and increases cell permeability, promoting the growth, spread and metastasis of tumors. Melatonin, the main hormone secreted by the pineal gland, may have a significant role in tumor suppression and has demonstrated antiangiogenic and antimetastatic effects. The aim of the present study was to analyze the cell viability, migration and invasion, as well as the expression of proangiogenic proteins VEGF and HIF-1α, in HepG2 hepatocarcinoma cells, following treatment with melatonin. Cells were cultured and cell viability was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The expression of proangiogenic proteins VEGF and HIF-1α, under conditions of normoxia and hypoxia, was verified using immunocytochemistry and quantified by densitometry. The analysis of the processes of cell migration and invasion was performed in a Boyden chamber. The MTT assay revealed a reduction in cell viability (P=0.018) following treatment with 1 mM melatonin for 24 h. The expression of proangiogenic proteins VEGF and HIF-1α was reduced in cells treated with 1 mM melatonin for 24 h in normoxic (P<0.001) and hypoxic (P<0.001) conditions, compared with the control group and with induced hypoxia alone. The rate of cell migration and invasion was additionally reduced in cells treated with 1 mM melatonin for 48 h when compared with the control group (P=0.496). The results of the present study suggest that melatonin may have an antiproliferative, antiangiogenic and antimetastatic role in hepatocarcinoma cells and may present a novel therapeutic option for the treatment of liver cancer.

Melatonin Pretreatment Enhances the Homing of Bone Marrow-derived Mesenchymal Stem Cells Following Transplantation in a Rat Model of Liver Fibrosis

Background:

Bone marrow-derived mesenchymal stem cells (BMMSCs) transplantation has been considered as a promising milestone in liver fibrosis treatment. However, low amounts of homing are a major obstacle. We aimed to investigate the role of melatonin pretreatment in BMMSC homing into experimental liver fibrosis.

Methods:

BMMSCs were obtained, grown, propagated and preconditioned with 5 µM melatonin and analyzed for multipotency and immunophenotypic features at passage three. The cells were labelled with CM-Dil and infused into the rats received the i.p. injection of carbon tetrachloride (CCl₄) for five weeks to induce liver fibrosis. Animals were divided into two groups: One group received BMMSCs, whereas the other group received melatonin-pretreated BMMSCs (MT-BMMSCs). After cell injection at 72 h, animals were sacrificed, and the liver tissues were assessed for further evaluations: fibrosis using Masson’s trichrome and hematoxylin and eosin staining and homing using fluorescent microscopy and flow cytometry.

Results:

BMMSCs and MT-BMMSCs expressed a high level of CD44 but low levels of CD11b, CD45 and CD34 (for all P≤0.05) and were able to differentiate into adipocytes and Schwann cells. CCl₄ induction resulted in extensive collagen deposition, tissue disruption and fatty accumulation with no obvious difference between the two groups. There was a significant increase in homing of MT-BMMSCs in both florescent microscopy (P≤0.001) and flow cytometry (P≤0.01) assays, as compared with non-treated BMMSCs.

Conclusion:

This study indicates the improved homing potential of BMMSCs in pretreatment with melatonin. Therefore, this strategy may represent an applied approach for improving the stem cell therapy of liver fibrosis.

Bone marrow-derived mesenchymal stem cells effectively regenerate fibrotic liver in bile duct ligation rat model

Mesenchymal stem cells (MSCs) have attracted lots of attention for the treatment of acute liver failure and end-stage liver diseases. This study aimed at investigating the fundamental mechanism by which bone marrow-derived MSCs (BM-MSCs) induce liver regeneration of fibrotic liver in rats. Rats underwent bile duct ligation (BDL) surgery and four weeks later they were treated with either BM-MSCs (3 × 10(6) cells /rat, once, tail vein injection) or silymarin (100 mg/kg, daily, orally) for four weeks. Liver function tests and hepatic oxidative stress were determined. Hepatic injury and fibrosis were assessed by H and E, Sirus red staining and immunohistochemical expression of α-smooth muscle actin (α-SMA). Hepatocyte growth factor (HGF) and the gene expression of cytokeratin-19 (CK-19) and matrix metalloproteinase-2 (MMP-2) in liver tissue were determined. BDL induced cholestatic liver injury characterized by elevated ALT and AST activities, bilirubin and decreased albumin. The architecture damage was staged as Metavir score: F3, A3. Fibrosis increased around proliferating bile duct as indicated by sirus red staining and α-SMA immunostaining. Fibrogenesis was favored over fibrolysis and confirmed by decreased HGF with increased expression of CK-19, but decreased MMP-2 expression. BM-MSCs treatment restored deteriorated liver functions and restored the histological changes, resolved fibrosis by improving liver regenerative capabilities (P < 0.001), increases in HGF and MMP-2 mRNA and downregulating CK-19 mRNA. Sliymarin, however, induced similar but less prominent effects compared to BM-MSCs. In conclusion, liver regenerative capabilities can be stimulated by BM-MSCs via augmentation of HGF that subsequently up-regulate MMP-2 mRNA while downregulating CK-19 mRNA.

Bone marrow mononuclear cell transplantation improves mitochondrial bioenergetics in the liver of cholestatic rats

Mitochondrial dysfunction has been associated with liver cholestatis. Toxic bile salt accumulation leads to chronic injury with mitochondrial damage, ROS increase and apoptosis, resulting in liver dysfunction. This study aimed to analyze mitochondrial bioenergetics in rats with hepatic fibrosis induced by bile duct ligation (BDL) after BMMNC transplantation. Livers were collected from normal rats, fibrotic rats after 14 and 21 days of BDL (F14d and F21d) and rats that received BMMNC at 14 days of BDL, analyzed after 7 days. F21d demonstrated increased collagen I content and consequently decrease after BMMNC transplantation. Both F14d and F21d had significantly reduced mitochondrial oxidation capacity and increased mitochondrial uncoupling, which were restored to levels similar to those of normal group after BMMNC transplantation. In addition, F21d had a significantly increase of UCP2, and reduced PGC-1α content. However, after BMMNC transplantation both proteins returned to levels similar to normal group. Moreover, F14d had a significantly increase in 4-HNE content compared to normal group, but after BMMNC transplantation 4-HNE content significantly reduced, suggesting oxidative stress reduction. Therefore, BMMNC transplantation has a positive effect on hepatic mitochondrial bioenergetics of cholestatic rats, increasing oxidative capacity and reducing oxidative stress, which, in turn, contribute to liver function recover.

Association of MMP7 -181A→G Promoter Polymorphism with Gastric Cancer Risk: INFLUENCE OF NICOTINE IN DIFFERENTIAL ALLELE-SPECIFIC TRANSCRIPTION VIA INCREASED PHOSPHORYLATION OF cAMP-RESPONSE ELEMENT-BINDING PROTEIN (CREB)

Elevated expression of matrix metalloproteinase7 (MMP7) has been demonstrated to play a pivotal role in cancer invasion. The -181A→G (rs11568818) polymorphism in the MMP7 promoter modulates gene expression and possibly affects cancer progression. Here, we evaluated the impact of -181A→G polymorphism on MMP7 promoter activity and its association with gastric cancer risk in eastern Indian case-control cohorts (n = 520). The GG genotype as compared with the AA genotype was predisposed (p = 0.02; odds ratio = 1.9, 95% confidence interval = 1.1-3.3) to gastric cancer risk. Stratification analysis showed that tobacco addiction enhanced gastric cancer risk in GG subjects when compared with AA subjects (p = 0.03, odds ratio = 2.46, and 95% confidence interval = 1.07-5.68). Meta-analysis revealed that tobacco enhanced the risk for cancer more markedly in AG and GG carriers. Activity and expression of MMP7 were significantly higher in GG than in AA carriers. In support, MMP7 promoter-reporter assays showed greater transcriptional activity toward A to G transition under basal/nicotine-induced/cAMP-response element-binding protein (CREB) overexpressed conditions in gastric adenocarcinoma cells. Moreover, nicotine (a major component of tobacco) treatment significantly up-regulated MMP7 expression due to enhanced CREB phosphorylation followed by its nuclear translocation in gastric adenocarcinoma cells. Furthermore, chromatin immunoprecipitation experiments revealed higher binding of phosphorylated CREB with the -181G than the -181A allele. Altogether, specific binding of phosphorylated CREB to the G allele-carrying promoter enhances MMP7 gene expression that is further augmented by nicotine due to increased CREB phosphorylation and thereby increases the risk for gastric cancer.

Multiple sclerosis: the role of melatonin and N-acetylserotonin

Multiple sclerosis (MS) is an immune mediated disorder that is under intensive investigation in an attempt to improve on available treatments. Many of the changes occurring in MS, including increased mitochondrial dysfunction, pain reporting and depression may be partly mediated by increased indoleamine 2,3-dioxygenase, which drives tryptophan to the production of neuroregulatory tryptophan catabolites and away from serotonin, N-acetylserotonin and melatonin production. The consequences of decreased melatonin have classically been attributed to circadian changes following its release from the pineal gland. However, recent data shows that melatonin may be produced by all mitochondria containing cells to some degree, including astrocytes and immune cells, thereby providing another important MS treatment target. As well as being a powerful antioxidant, anti-inflammatory and antinociceptive, melatonin improves mitochondrial functioning, partly via increased oxidative phosphorylation. Melatonin also inhibits demyelination and increases remyelination, suggesting that its local regulation in white matter astrocytes by serotonin availability and apolipoprotein E4, among other potential factors, will be important in the etiology, course and treatment of MS. Here we review the role of local melatonin and its precursors, N-acetylserotonin and serotonin, in MS.

Prolonged exposure of cholestatic rats to complete dark inhibits biliary hyperplasia and liver fibrosis

Biliary hyperplasia and liver fibrosis are common features in cholestatic liver disease. Melatonin is synthesized by the pineal gland as well as the liver. Melatonin inhibits biliary hyperplasia of bile duct-ligated (BDL) rats. Since melatonin synthesis (by the enzyme serotonin N-acetyltransferase, AANAT) from the pineal gland increases after dark exposure, we hypothesized that biliary hyperplasia and liver fibrosis are diminished by continuous darkness via increased melatonin synthesis from the pineal gland. Normal or BDL rats (immediately after surgery) were housed with light-dark cycles or complete dark for 1 wk before evaluation of 1) the expression of AANAT in the pineal gland and melatonin levels in pineal gland tissue supernatants and serum; 2) biliary proliferation and intrahepatic bile duct mass, liver histology, and serum chemistry; 3) secretin-stimulated ductal secretion (functional index of biliary growth); 4) collagen deposition, liver fibrosis markers in liver sections, total liver, and cholangiocytes; and 5) expression of clock genes in cholangiocytes. In BDL rats exposed to dark there was 1) enhanced AANAT expression/melatonin secretion in pineal gland and melatonin serum levels; 2) improved liver morphology, serum chemistry and decreased biliary proliferation and secretin-stimulated choleresis; and 4) decreased fibrosis and expression of fibrosis markers in liver sections, total liver and cholangiocytes and reduced biliary expression of the clock genes PER1, BMAL1, CLOCK, and Cry1. Thus prolonged dark exposure may be a beneficial noninvasive therapeutic approach for the management of biliary disorders.

Hepatoprotective Effect of Fermented Soybean (Nutrient Enriched Soybean Tempeh) against Alcohol-Induced Liver Damage in Mice

Recently, soybean tempeh has received great attention due to many advantages such as higher nutritional value, lower production cost, and shorter fermentation time. In this study, the in vivo hepatoprotective and antioxidant effects of nutrient enriched soybean tempeh (NESTE) were determined. NESTE fermentation process which involved anaerobic incubation was previously proclaimed to increase the content of amino acids and antioxidant properties remarkably. The evaluation of histological sections, serum biochemical markers (aspartate aminotransferase (AST), alanine aminotransferase (ALT), and cholesterol and triglycerides (TG)), liver immune response level (nitric oxide (NO)) and liver antioxidant level (superoxide dismutase (SOD), ferric reducing antioxidant power (FRAP), and malondialdehyde (MDA)) was conducted in order to compare the effects of nonfermented soybean extract (SBE) and fermented soybean extract (NESTE) on alcohol-induced liver damage in mice. Results demonstrated that 1000 mg/kg of NESTE can significantly reduce the levels of AST, ALT, cholesterol, TG, MDA, and NO. On the other hand, it also raised the level of SOD and FRAP. Furthermore, the histological examination on 1000 mg/kg NESTE treatment group showed that this extract was capable of recovering the damaged hepatocytes to their normal structures. Thus, it can be concluded that NESTE produced through fermentation process was able to enhance hepatoprotective and antioxidant effects in vivo.

Melatonin mediates protective effects on inflammatory response induced by interleukin-1 beta in human mesenchymal stem cells

Joint diseases like osteoarthritis usually are accompanied with inflammatory processes, in which pro-inflammatory cytokines mediate the generation of intracellular reactive oxygen species (ROS) and compromise survival of subchondral osteoblasts. Melatonin is capable of manipulating bone formation and osteogenic differentiation of mesenchymal stem cells (MSCs). The aim of this work was to investigate the anti-inflammatory effect of melatonin on MSC proliferation and osteogenic differentiation in the absence or presence of interleukin-1 beta (IL-1β), which was used to induce inflammation. Our data showed that melatonin improved cell viability and reduced ROS generation in MSCs in a dose-dependent manner. When exposed to 10 ng/mL IL-1β, various concentrations of melatonin resulted in significant reduction of ROS by 34.9% averagely. Luzindole as a melatonin receptor antagonist reversed the anti-oxidant effect of melatonin in MSCs with co-exposure to IL-1β. Real-time RT-PCR data suggested that melatonin treatment up-regulated the expression of CuZnSOD and MnSOD, while down-regulated the expression of Bax. To investigate the effect of melatonin on osteogenesis, MSCs were cultured in osteogenic differentiation medium supplemented with IL-1β, melatonin, or luzindole. After exposed to IL-1β for 21 days, 1 μm melatonin treatment significantly increased the levels of type I collagen, ALP, and osteocalcin, and 100 μm melatonin treatment yielded the highest level of osteopontin. Our study demonstrated that melatonin maintained MSC survival and promoted osteogenic differentiation in inflammatory environment induced by IL-1β, suggesting melatonin treatment could be a promising method for bone regenerative engineering in future studies.

Aqueous extract of Artemisia capillaris exerts hepatoprotective action in alcohol-pyrazole-fed rat model

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia capillaris, also called "InJin" in Korean, has been widely used to treat various hepatic disorders in traditional Oriental medicine.

AIMS

The purpose of this study is to evaluate the hepatoprotective effect of Artemisia capillaris (aqueous extract, WAC) on alcoholic liver injury.

MATERIALS AND METHODS

Liver injury was induced by oral administration of 30% alcohol (10 mL/kg, twice per day) plus pyrazole (PRZ, 30 mg/kg) with/without WAC (50, 100mg/kg, orally once per day) or silymarin (50mg/kg) for 10 days. The hepatoprotective effects were assessed by observing histopathological changes, hepatic transaminase enzymes, hepatic oxidation and antioxidant parameters, inflammatory cytokines, and alcohol metabolic enzymes in serum and hepatic gene expression level, respectively.

RESULTS

Alcohol-PRZ treatment drastically increased the serum levels of aspartate transaminase (AST), alanine transaminase (ALT), and malondialdehyde (MDA) levels in serum and liver tissues while these changes were significantly ameliorated by WAC administration (p<0.05 or 0.01). The prominent microvesicular steatosis and mild necrosis in hepatic histopathology were induced by alcohol-PRZ treatment, but notably attenuated by WAC administration. Moreover, the alcohol-PRZ treatment-induced depletions of the antioxidant components including glutathione content, total antioxidant capacity (TAC), activities of glutathione peroxidase (GSH-Px), reductase (GSH-Rd), catalase, and superoxide dismutase (SOD) were significantly ameliorated by WAC administration (p<0.05, except GSH-Rd). These results were in accordance with the modulation of NF-E2-related factor (Nrf2) and heme oxygenase-1 (HO-1) gene expression. Alcohol-PRZ treatment increased the levels of tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-β) in hepatic tissues. However they were significantly normalized by WAC administration (p<0.05 or 0.01). In addition, WAC administration significantly attenuated the alterations of aldehyde dehydrogenase (ALDH) level in serum and hepatic gene expressions of ALDH and alcohol dehydrogenase (ADH).

CONCLUSIONS

These results support the relevance in clinical use of Artemisia capillaris for alcohol-associated hepatic disorders. The underlying mechanisms may involve both enhancement of antioxidant activities and modulation of proinflammatory cytokines.

Melatonin inhibits matrix metalloproteinase-9 activity by binding to its active site

The zinc-dependent matrix metalloproteinases (MMPs) are key enzymes associated with extracellular matrix (ECM) remodeling; they play critical roles under both physiological and pathological conditions. MMP-9 activity is linked to many pathological processes, including rheumatoid arthritis, atherosclerosis, gastric ulcer, tumor growth, and cancer metastasis. Specific inhibition of MMP-9 activity may be a promising target for therapy for diseases characterized by dysregulated ECM turnover. Potent MMP-9 inhibitors including an indole scaffold were recently reported in an X-ray crystallographic study. Herein, we addressed whether melatonin, a secretory product of pineal gland, has an inhibitory effect on MMP-9 function. Gelatin zymographic analysis showed a significant reduction in pro- and active MMP-9 activity in vitro in a dose- and time-dependent manner. In addition, a human gastric adenocarcinoma cell line (AGS) exhibited a reduced (~50%) MMP-9 expression when incubated with melatonin, supporting an inhibitory effect of melatonin on MMP-9. Atomic-level interaction between melatonin and MMP-9 was probed with computational chemistry tools. Melatonin docked into the active site cleft of MMP-9 and interacted with key catalytic site residues including the three histidines that form the coordination complex with the catalytic zinc as well as proline 421 and alanine 191. We hypothesize that under physiological conditions, tight binding of melatonin in the active site might be involved in reducing the catalytic activity of MMP-9. This finding could provide a novel approach to physical docking of biomolecules to the catalytic site of MMPs, which inhibits this protease, to arrest MMP-9-mediated inflammatory signals.

A review of the molecular aspects of melatonin's anti-inflammatory actions: recent insights and new perspectives

Melatonin is a highly evolutionary conserved endogenous molecule that is mainly produced by the pineal gland, but also by other nonendocrine organs, of most mammals including man. In the recent years, a variety of anti-inflammatory and antioxidant effects have been observed when melatonin is applied exogenously under both in vivo and in vitro conditions. A number of studies suggest that this indole may exert its anti-inflammatory effects through the regulation of different molecular pathways. It has been documented that melatonin inhibits the expression of the isoforms of inducible nitric oxide synthase and cyclooxygenase and limits the production of excessive amounts of nitric oxide, prostanoids, and leukotrienes, as well as other mediators of the inflammatory process such as cytokines, chemokines, and adhesion molecules. Melatonin's anti-inflammatory effects are related to the modulation of a number of transcription factors such as nuclear factor kappa B, hypoxia-inducible factor, nuclear factor erythroid 2-related factor 2, and others. Melatonin's effects on the DNA-binding capacity of transcription factors may be regulated through the inhibition of protein kinases involved in signal transduction, such as mitogen-activated protein kinases. This review summarizes recent research data focusing on the modulation of the expression of different inflammatory mediators by melatonin and the effects on cell signaling pathways responsible for the indole's anti-inflammatory activity. Although there are a numerous published reports that have analyzed melatonin's anti-inflammatory properties, further studies are necessary to elucidate its complex regulatory mechanisms in different cellular types and tissues.

Geroprotectors as a novel therapeutic strategy for COPD, an accelerating aging disease

Chronic obstructive pulmonary disease (COPD) progresses very slowly and the majority of patients are therefore elderly. COPD is characterized by an abnormal persistent inflammatory response to noxious environmental stimuli and there are increasing evidences for a close relationship between premature aging and chronic inflammatory diseases. Thus, COPD is considered to be a disease of an accelerating aging. In this review, we collected the evidence for roles of aging on pathogenesis of COPD and considered future therapeutic strategy for COPD based on this senescence hypothesis. Since calorie restriction has been proved to extend lifespan, many efforts were made to clarify the molecular mechanism of aging. Aging is defined as the progressive decline of homeostasis that occurs after the reproductive phase of life is complete, leading to an increasing risk of disease or death due to impaired DNA repair after damage by oxidative stress or telomere shortening as a result of repeated cell division. During aging, pulmonary function progressively deteriorates; innate immunity is impaired and pulmonary inflammation increases, accompanied by structural changes, such as an enlargement of airspaces. Noxious environmental gases, such as cigarette smoke, may worsen these aging-related events in the lung or accelerate aging of the lung due to reduction in anti-aging molecules and/or stimulation of aging molecules. Aging signaling are complex but conserved in divert species, such as worm, fruit fry, rodent and humans. Especially the insulin like growth factor (IGF-1) signaling was well documented. Geroprotectors are therapeutics that affect the root cause of aging and age-related diseases, and thus prolong the life-span of animals. Most of geroprotectors such as melatonin, metformin, rapamycin and resveratrol are anti-oxidant or anti-aging molecule regulators. Therefore, geroprotection for the lung might be an attractive approach for the treatment of COPD by preventing premature aging of lung.

Melatonin inhibits matrix metalloproteinase-9 (MMP-9) activation in the lipopolysaccharide (LPS)-stimulated RAW 264.7 and BV2 cells and a mouse model of meningitis

We explored anti-inflammatory potential of melatonin against the lipopolysaccharide (LPS)-induced inflammation in vivo and in vitro. RAW 264.7 and BV2 cells were stimulated by LPS, followed by the treatment with melatonin or vehicle at various time intervals. In a mouse model of meningitis induced by LPS, melatonin (5mg/kg) or vehicle was intravenously injected at 30min postinsult. The activity of matrix metalloproteinase-2 (MMP-2) and metalloproteinase-9 (MMP-9) was determined by gelatin zymography. Nuclear factor-kappa B (NFκB) translocation and binding activity were determined by immunocytochemistry and electrophoretic mobility shift assay (EMSA). Our results showed that either pretreatment or cotreatment with melatonin at 50-500 μm effectively inhibited the LPS-induced proMMP-9 activation in the RAW 264.7 and BV2 cells, respectively (P<0.05). This melatonin-induced proMMP-9 inhibition remained effective when treatment was delayed up to 2 and 6hr postinsult for RAW 264.7 and BV2 cells, respectively (P<0.05 for both groups). Additionally, melatonin significantly attenuated the rises of circulatory and cerebral MMP-9 activity, respectively (P<0.05) and reduced the loss of body weight (P<0.05) in mice with meningitis. Moreover, melatonin (50μm) effectively inhibited nuclear factor-kappa B (NFκB) translocation and binding activity in the LPS-treated RAW 264.7 and BV2 cells, respectively (P<0.05). These results demonstrate direct inhibitory actions of melatonin against postinflammatory NFκB translocation and MMP-9 activation and highlight its ability to inhibit systemic and cerebral MMP-9 activation following brain inflammation.