Melatonin induces calcium mobilization and influences cell proliferation independently of MT1/MT2 receptor activation in rat pancreatic stellate cells

Melatonin Interplay in Physiology and Disease-The Fountain of Eternal Youth Revisited

Melatonin (N-acetyl-5-methoxytryptamine) is a hormone associated with the regulation of biological rhythms. The indoleamine is secreted by the pineal gland during the night, following a circadian rhythm. The highest plasmatic levels are reached during the night, whereas the lowest levels are achieved during the day. In addition to the pineal gland, other organs and tissues also produce melatonin, like, for example, the retina, Harderian glands, gut, ovaries, testes, skin, leukocytes, or bone marrow. The list of organs is extensive, including the cerebellum, airway epithelium, liver, kidney, adrenals, thymus, thyroid, pancreas, carotid body, placenta, and endometrium. At all these locations, the availability of melatonin is intended for local use. Interestingly, a decline of the circadian amplitude of the melatonin secretion occurs in old subjects in comparison to that found in younger subjects. Moreover, genetic and environmental factors are the primary causes of diseases, and oxidative stress is a key contributor to most pathologies. Numerous studies exist that show interesting effects of melatonin in different models of disease. Impairment in its secretion might have deleterious consequences for cellular physiology. In this regard, melatonin is a natural compound that is a carrier of a not yet completely known potential that deserves consideration. Thus, melatonin has emerged as a helpful ally that could be considered as a guard with powerful tools to orchestrate homeostasis in the body, majorly based on its antioxidant effects. In this review, we provide an overview of the widespread actions of melatonin against diseases preferentially affecting the elderly.

Melatonin Regulates the Expression of VEGF and HOXA10 in Bovine Endometrial Epithelial Cells through the SIRT1/PI3K/AKT Pathway

Melatonin plays a critical role in regulating embryo attachment in ruminants. While numerous studies have investigated its effects on early embryo development in vitro, the precise mechanisms by which melatonin influences the receptivity of endometrial epithelial cells in dairy cows remain unclear. The prerequisite for embryo implantation is the specific physiological condition of the endometrium that allows the embryo to implant, also known as endometrial receptivity. In addition to this, endometrial cells undergo processes such as proliferation, differentiation, and renewal, which makes the embryo more easily implanted. In this study, bovine endometrial epithelial cells were cultured and treated with melatonin, Silent Information Regulator 1 (SIRT1) inhibitor (EX527), and protein kinase B (AKT) phosphorylation inhibitor (periposine). RT-qPCR, Western blot, and immunofluorescence analysis were performed to investigate the effects of melatonin on the expression of target gene (SIRT1); cell proliferative genes, phosphatidylinositol-4,5-bisphosphate 3-Kinase (PI3K), AKT, cyclinD1, cyclinE1; and receptive genes (Leukemia Inhibitory Factor (LIF), Vascular Endothelial Growth Factor (VEGF), Homeobox Structure Gene 10 (HOXA10)). Additionally, microRNA (miRNA) mimics and inhibitors were used to transfect the cells to study the regulatory relationship between miRNA and receptive genes. Results indicated that melatonin activates the PI3K/AKT signaling pathway, upregulates cyclinD1 and cyclinE1, and promotes the proliferation of bovine endometrial epithelial cells. Melatonin also upregulated the expression of VEGF and HOXA10 and downregulated the expression of bta-miR-497 and bta-miR-27a-3p through SIRT1/PI3K/AKT signaling pathway. Further, bta-miR-497 and bta-miR-27a-3p were found to negatively regulate VEGF and HOXA10, respectively. Therefore, melatonin regulates the expression of VEGF and HOXA10 through the SIRT1/PI3K/AKT pathway and promotes the establishment of receptivity in bovine endometrial epithelial cells.

Melatonin controls cell proliferation and modulates mitochondrial physiology in pancreatic stellate cells

We have investigated the effects of melatonin on major pathways related with cellular proliferation and energetic metabolism in pancreatic stellate cells. In the presence of melatonin (1 mM, 100 µM, 10 µM, or 1 µM), decreases in the phosphorylation of c-Jun N-terminal kinase and of p44/42 and an increase in the phosphorylation of p38 were observed. Cell viability dropped in the presence of melatonin. A rise in the phosphorylation of AMP-activated protein kinase was detected in the presence of 1 mM and 100 µM melatonin. Treatment with 1 mM melatonin decreased the phosphorylation of protein kinase B, whereas 100 µM and 10 µM melatonin increased its phosphorylation. An increase in the generation of mitochondrial reactive oxygen species and a decrease of mitochondrial membrane potential were noted following melatonin treatment. Basal and maximal respiration, ATP production by oxidative phosphorylation, spare capacity, and proton leak dropped in the presence of melatonin. The expression of complex I of the mitochondrial respiratory chain was augmented in the presence of melatonin. Conversely, in the presence of 1 mM melatonin, decreases in the expression of mitofusins 1 and 2 were detected. The glycolysis and the glycolytic capacity were diminished in cells treated with 1 mM or 100 µM melatonin. Increases in the expression of phosphofructokinase-1 and lactate dehydrogenase were noted in cells incubated with 100 µM, 10 µM, or 1 µM melatonin. The expression of glucose transporter 1 was increased in cells incubated with 10 µM or 1 µM melatonin. Conversely, 1 mM melatonin decreased the expression of all three proteins. Our results suggest that melatonin, at pharmacological concentrations, might modulate mitochondrial physiology and energy metabolism in addition to major pathways involved in pancreatic stellate cell proliferation.

Melatonin modulates metabolic adaptation of pancreatic stellate cells subjected to hypoxia

Pancreatic stellate cells (PSCs), the main cell type responsible for the development of fibrosis in pancreatic cancer, proliferate actively under hypoxia. Melatonin has received attention as a potential antifibrotic agent due to its anti-proliferative actions on PSCs. In this work, we investigated the activation of the PI3K/Akt/mTOR pathway and the metabolic adaptations that PSCs undergo under hypoxic conditions, as well as the probable modulation by melatonin. Incubation of cells under hypoxia induced an increase in cell proliferation, and in the expression of alpha-smooth muscle actin and of collagen type 1. In addition, an increase in the phosphorylation of Akt was observed, whereas a decrease in the phosphorylation of PTEN and GSK-3b was noted. The phosphorylation of mTOR and its substrate p70 S6K was decreased under hypoxia. Treatment of PSCs with melatonin under hypoxia diminished cell proliferation, the levels of alpha-smooth muscle actin and of collagen type 1, the phosphorylation of Akt and increased phosphorylation of mTOR. Mitochondrial activity decreased in PSCs under hypoxia. A glycolytic shift was observed. Melatonin further decreased mitochondrial activity. Under hypoxia, no increase in autophagic flux was noted. However, melatonin treatment induced autophagy activation. Nevertheless, inhibition of this process did not induce detectable changes in the viability of cells treated with melatonin. We conclude that PSCs undergo metabolic adaptation under hypoxia that might help them survive and that pharmacological concentrations of melatonin modulate cell responses to hypoxia. Our results contribute to the knowledge of the mechanisms by which melatonin could modulate fibrosis within the pancreas.

Melatonin Induces Apoptosis and Modulates Cyclin Expression and MAPK Phosphorylation in Pancreatic Stellate Cells Subjected to Hypoxia

In certain diseases of the pancreas, pancreatic stellate cells form an important part of fibrosis and are critical for the development of cancer cells. A hypoxic condition develops within the tumor, to which pancreatic stellate cells adapt and are able to proliferate. The consequence is the growth of the tumor. Melatonin, the product of the pineal gland, is gaining attention as an agent with therapeutic potential against pancreatic cancers. Its actions on tumor cells lead, in general, to a reduction in cell viability and proliferation. However, its effects on pancreatic stellate cells subjected to hypoxia are less known. In this study, we evaluated the actions of pharmacological concentrations of melatonin (1 mM-1 µM) on pancreatic stellate cells subjected to hypoxia. The results show that melatonin induced a decrease in cell viability at the highest concentrations tested. Similarly, the incorporation of BrdU into DNA was diminished by melatonin. The expression of cyclins A and D also was decreased in the presence of melatonin. Upon treatment of cells with melatonin, increases in the expression of major markers of ER stress, namely BIP, phospho-eIF2α and ATF-4, were detected. Modulation of apoptosis was noticed as an increase in caspase-3 activation. In addition, changes in the phosphorylated state of p44/42, p38 and JNK MAPKs were detected in cells treated with melatonin. A slight decrease in the content of α-smooth muscle actin was detected in cells treated with melatonin. Finally, treatment of cells with melatonin decreased the expression of matrix metalloproteinases 2, 3, 9 and 13. Our observations suggest that melatonin, at pharmacological concentrations, diminishes the proliferation of pancreatic stellate cells subjected to hypoxia through modulation of cell cycle, apoptosis and the activation of crucial MAPKs. Cellular responses might involve certain ER stress regulator proteins. In view of the results, melatonin could be taken into consideration as a potential therapeutic agent for pancreatic fibrosis.

Melatonin Modulates the Antioxidant Defenses and the Expression of Proinflammatory Mediators in Pancreatic Stellate Cells Subjected to Hypoxia

Pancreatic stellate cells (PSC) play a major role in the formation of fibrotic tissue in pancreatic tumors. On its side, melatonin is a putative therapeutic agent for pancreatic cancer and inflammation. In this work, the actions of melatonin on PSC subjected to hypoxia were evaluated. Reactive oxygen species (ROS) generation reduced (GSH) and oxidized (GSSG) levels of glutathione, and protein and lipid oxidation were analyzed. The phosphorylation of nuclear factor erythroid 2-related factor (Nrf2), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB), and the regulatory protein nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor-alpha (IκBα) was studied. The expression of Nrf2-regulated antioxidant enzymes, superoxide dismutase (SOD) enzymes, cyclooxygenase 2 (COX-2), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were also studied. Total antioxidant capacity (TAC) was assayed. Finally, cell viability was studied. Under hypoxia and in the presence of melatonin generation of ROS was observed. No increases in the oxidation of proteins or lipids were detected. The phosphorylation of Nrf2 and the expression of the antioxidant enzymes catalytic subunit of glutamate-cysteine ligase, catalase, NAD(P)H-quinone oxidoreductase 1, heme oxygenase-1, SOD1, and of SOD2 were augmented. The TAC was increased. Protein kinase C was involved in the effects of melatonin. Melatonin decreased the GSH/GSSG ratio at the highest concentration tested. Cell viability dropped in the presence of melatonin. Finally, melatonin diminished the phosphorylation of NF-kB and the expression of COX-2, IL-6, and TNF-α. Our results indicate that melatonin, at pharmacological concentrations, modulates the red-ox state, viability, and the expression of proinflammatory mediators in PSC subjected to hypoxia.

The melatonin receptor antagonist luzindole induces the activation of cellular stress responses and decreases viability of rat pancreatic stellate cells

In this study, we have examined the effects of luzindole, a melatonin receptor-antagonist, on cultured pancreatic stellate cells. Intracellular free-Ca2+ concentration, production of reactive oxygen species (ROS), activation of mitogen-activated protein kinases (MAPK), endoplasmic reticulum stress and cell viability were analyzed. Stimulation of cells with the luzindole (1, 5, 10 and 50 μm) evoked a slow and progressive increase in intracellular free Ca2+ ([Ca2+ ]i ) towards a plateau. The effect of the compound on Ca2+ mobilization depended on the concentration used. Incubation of cells with the sarcoendoplasmic reticulum Ca2+ -ATPase inhibitor thapsigargin (1 μm), in the absence of Ca2+ in the extracellular medium, induced a transient increase in [Ca2+ ]i . In the presence of thapsigargin, the addition of luzindole to the cells failed to induce further mobilization of Ca2+ . Luzindole induced a concentration-dependent increase in ROS generation, both in the cytosol and in the mitochondria. This effect was smaller in the absence of extracellular Ca2+ . In the presence of luzindole the phosphorylation of p44/42 and p38 MAPKs was increased, whereas no changes in the phosphorylation of JNK could be noted. Moreover, the detection of the endoplasmic reticulum stress-sensor BiP was increased in the presence of luzindole. Finally, viability was decreased in cells treated with luzindole. Because cellular membrane receptors for melatonin have not been detected in pancreatic stellate cells, we conclude that luzindole could exert direct effects that are not mediated through its action on melatonin membrane receptors.

Pancreatic stellate cells exhibit adaptation to oxidative stress evoked by hypoxia

BACKGROUND INFORMATION

Pancreatic stellate cells play a key role in the fibrosis that develops in diseases such as pancreatic cancer. In the growing tumour, a hypoxia condition develops under which cancer cells are able to proliferate. The growth of fibrotic tissue contributes to hypoxia. In this study, the effect of hypoxia (1% O2 ) on pancreatic stellate cells physiology was investigated. Changes in intracellular free-Ca2+ concentration, mitochondrial free-Ca2+ concentration and mitochondrial membrane potential were studied by fluorescence techniques. The status of enzymes responsible for the cellular oxidative state was analyzed by quantitative reverse transcription-polymerase chain reaction, high-performance liquid chromatography, spectrophotometric and fluorimetric methods and by Western blotting analysis. Cell viability and proliferation were studied by crystal violet test, 5-bromo-2-deoxyuridine cell proliferation test and Western blotting analysis. Finally, cell migration was studied employing the wound healing assay.

RESULTS

Hypoxia induced an increase in intracellular and mitochondrial free-Ca2+ concentration, whereas mitochondrial membrane potential was decreased. An increase in mitochondrial reactive oxygen species production was observed. Additionally, an increase in the oxidation of proteins and lipids was detected. Moreover, cellular total antioxidant capacity was decreased. Increases in the expression of superoxide dismutase 1 and 2 were observed and superoxide dismutase activity was augmented. Hypoxia evoked a decrease in the oxidized/reduced glutathione ratio. An increase in the phosphorylation of nuclear factor erythroid 2-related factor and in expression of the antioxidant enzymes catalytic subunit of glutamate-cysteine ligase, catalase, NAD(P)H-quinone oxidoreductase 1 and heme oxygenase-1 were detected. The expression of cyclin A was decreased, whereas expression of cyclin D and the content of 5-bromo-2-deoxyuridine were increased. This was accompanied by an increase in cell viability. The phosphorylation state of c-Jun NH2 -terminal kinase was increased, whereas that of p44/42 and p38 was decreased. Finally, cells subjected to hypoxia maintained migration ability.

CONCLUSIONS AND SIGNIFICANCE

Hypoxia creates pro-oxidant conditions in pancreatic stellate cells to which cells adapt and leads to increased viability and proliferation.

Melatonin promotes Schwann cell dedifferentiation and proliferation through the Ras/Raf/ERK and MAPK pathways, and glial cell-derived neurotrophic factor expression

Upon peripheral nerve injury (PNI), continuous proliferation of Schwann cells is critical for axon regeneration and tubular reconstruction for nerve regeneration. Melatonin is a hormone that is able to induce proliferation in various cell types. In the present study, the effects of melatonin on promoting Schwann cell proliferation and the molecular mechanism involved were investigated. The present results showed that melatonin enhanced the melatonin receptors (MT1 and MT2) expression in Schwann cells. Melatonin induced Schwann cell dedifferentiation into progenitor-like Schwann cells, as observed by immunofluorescence staining, which showed Sox2 marker expression. In addition, melatonin enhanced Schwann cell proliferation, mediated by the upregulation of glial cell-derived neurotropic factor (GNDF) and protein kinase C (PKC). Furthermore, the Ras/Raf/ERK and MAPK signaling pathways were also involved in Schwann cell dedifferentiation and proliferation. In conclusion, melatonin induced Schwann cell dedifferentiation and proliferation via the Ras/Raf/ERK, MAPK and GDNF/PKC pathways. The present results suggested that melatonin could be used to enhance the recovery of PNI.

Melatonin improves uterine-conceptus interaction via regulation of SIRT1 during early pregnancy

Melatonin has been shown to improve in vitro fertilization and offspring survival after bacterial infection, but its role in regulating maternal-fetal communication during early pregnancy has not been investigated. Results of this study demonstrated expression of abundant melatonin receptors in conceptus and endometrium during early pregnancy. In gilts, expression of melatonin receptor 1A (MTNR1A or MT1) and melatonin receptor 1B (MTNR1B or MT2) increased in trophectoderm (Tr) and uterine luminal epithelium (LE) with advancing days during early pregnancy in a different manner. Melatonin increased proliferation and migration of porcine trophectoderm (pTr) cell, the percent pTr cells in the G2 phase of the cell cycle, and the expression of implantation-related genes by pTr cells and endometrial luminal epithelium (pLE). Melatonin also attenuated the production of LPS-induced pro-inflammatory cytokines and tunicamycin-induced endoplasmic reticulum (ER) stress-sensing proteins. The expression of sirtuin 1 (SIRT1) as a potential target of melatonin increased between Days 9 and 14 of gestation. Co-treatment with SIRT1 inhibitor EX527 and melatonin restored cell-cell interactions through PI3K and MAPK signaling. Knockdown of SIRT1 decreased the expression of implantation-related genes, as well as migration of pTr and pLE cells. The expression of microRNAs regulated by SIRT1 was suppressed in response to melatonin. Furthermore, melatonin significantly increased lipopolysaccharide (LPS)-reduced fertilization and embryogenesis in zebrafish model. These results suggest that melatonin may improve the uterine-conceptus interactions via the regulation of SIRT1 during early pregnancy.

Melatonin modulates proliferation of pancreatic stellate cells through caspase-3 activation and changes in cyclin A and D expression

In this study, the effects of melatonin (1 μM-1 mM) on pancreatic stellate cells (PSC) have been examined. Cell viability and proliferation, caspase-3 activation, and the expression of cyclin A and cyclin D were analyzed. Our results show that melatonin decreased PSC viability in a time- and concentration-dependent manner. This effect was not inhibited by treatment of cells with MT1, MT2, calmodulin, or ROR-alpha inhibitors prior to melatonin addition. Activation of caspase-3 in response to melatonin was detected. The expression of cyclin A and cyclin D was decreased in cells treated with melatonin. Finally, changes in BrdU incorporation into the newly synthesized DNA of proliferating cells were also observed in the presence of melatonin. We conclude that melatonin, at pharmacological concentrations, modulates proliferation of PSC through activation of apoptosis and involving crucial regulators of the cell cycle. These actions might not require specific melatonin receptors. Our observations suggest that melatonin, at high doses, could potentially exert anti-fibrotic effects and, thus, could be taken into consideration as supportive treatment in the therapy of pancreatic diseases.

Melatonin modulates red-ox state and decreases viability of rat pancreatic stellate cells

In this work we have studied the effects of pharmacological concentrations of melatonin (1 µM-1 mM) on pancreatic stellate cells (PSC). Cell viability was analyzed by AlamarBlue test. Production of reactive oxygen species (ROS) was monitored following CM-H2DCFDA and MitoSOX Red-derived fluorescence. Total protein carbonyls and lipid peroxidation were analyzed by HPLC and spectrophotometric methods respectively. Mitochondrial membrane potential (ψm) was monitored by TMRM-derived fluorescence. Reduced (GSH) and oxidized (GSSG) levels of glutathione were determined by fluorescence techniques. Quantitative reverse transcription-polymerase chain reaction was employed to detect the expression of Nrf2-regulated antioxidant enzymes. Determination of SOD activity and total antioxidant capacity (TAC) were carried out by colorimetric methods, whereas expression of SOD was analyzed by Western blotting and RT-qPCR. The results show that melatonin decreased PSC viability in a concentration-dependent manner. Melatonin evoked a concentration-dependent increase in ROS production in the mitochondria and in the cytosol. Oxidation of proteins was detected in the presence of melatonin, whereas lipids oxidation was not observed. Depolarization of ψm was noted with 1 mM melatonin. A decrease in the GSH/GSSG ratio was observed, that depended on the concentration of melatonin used. A concentration-dependent increase in the expression of the antioxidant enzymes catalytic subunit of glutamate-cysteine ligase, catalase, NAD(P)H-quinone oxidoreductase 1 and heme oxygenase-1 was detected in cells incubated with melatonin. Finally, decreases in the expression and in the activity of superoxide dismutase were observed. We conclude that pharmacological concentrations melatonin modify the redox state of PSC, which might decrease cellular viability.

Theophylline exerts complex anti-ageing and anti-cytotoxicity effects in human skin ex vivo

OBJECTIVE

Theophylline is a phosphodiesterase inhibitor that is being used clinically for asthma therapy. In addition, it is recognized as a cosmetic agent with possible anti-ageing and anti-oxidative properties. Nevertheless, how it affects human skin is still poorly examined.

METHODS

Theophylline (10 or 100 µM) was administered to the culture medium of full-thickness human skin ex vivo for 24 or 72 h.

RESULTS

Theophylline stimulated protein expression of the anti-oxidant metallothionein-1 and mRNA levels of collagen I and III. Assessment of fibrillin-1 immunohistology revealed enhanced structural stability of dermal microfibrils. Theophylline also exerted extracellular matrix-protective effects by decreasing MMP-2 and MMP-9 mRNA levels, partially antagonizing the effects of menadione, the potent, toxic ROS donor. In addition, it decreased menadione-stimulated epidermal keratinocytes apoptosis. Interestingly, theophylline also increased the level of intracutaneously produced melatonin, that is the most potent ROS-protective and DNA damage repair neuromediator, and tendentially increased protein expression of MT1, the melatonin receptor. Theophylline also increased the expression of keratin 15, the stem cell marker, in the epidermal basal layer but did not change mitochondrial activity or epidermal pigmentation.

CONCLUSION

This ex vivo pilot study in human skin shows that theophylline possesses several interesting complex skin-protective properties. It encourages further examination of theophylline as a topical candidate for anti-ageing treatment.

Ultraviolet B irradiation induced Nrf2 degradation occurs via activation of TRPV1 channels in human dermal fibroblasts

Ultraviolet (UV) irradiation causes cellular oxidative stress. Under redox imbalance, Keap1-dependent Nrf2 degradation is minimal. In this study, we examined the role of Ca²⁺ in Nrf2 homeostasis after UVB irradiation using human dermal fibroblasts. UVB irradiation stimulates 12-lipoxygenase and the product 12-hydroxyeicosatetraenoic acid then activates TRPV1 increasing the cell's cytosolic Ca²⁺ concentration. UVB irradiation induced reactive oxygen species generation and apoptosis are inhibited in the absence of Ca²⁺ or in the presence of either a 12-lipoxygenase inhibitor or a TRPV1 inhibitor during and after UVB irradiation. Thus, the Ca²⁺ increase via TRPV1 is a critical factor in UVB irradiation induced oxidative stress. UVB irradiation induces a Ca²⁺ dependent Nrf2 degradation and thus activation of TRPV1 with 12-hydroxyeicosatetraenoic acid also decreasing Nrf2 levels. UVB irradiation induced Nrf2 degradation is inhibited by co-treatment of cells with W-7, cyclosporin A, SB-216763 or MG-132, which are inhibitors of calmodulin, calcineurin, GSK3β and the proteasome, respectively. Furthermore, UVB irradiation in parallel induces GSK3β dephosphorylation in a Ca²⁺ dependent manner. Co-immunoprecipitation showed that UVB irradiation induces an increase in Nrf2 phosphorylation, an increase in the binding of β-TrCP and Nrf2, and an increase in Nrf2 ubiquitination; these effects are all Ca²⁺ dependent. These findings suggest that UVB irradiation induced GSK3β activation in a Ca²⁺ dependent manner, which then stimulates the phosphorylation and ubiquitination of Nrf2 via β-TrCP. Indeed, silencing of β-TrCP was found to inhibit UVB irradiation-induced oxidative stress, Nrf2 degradation and apoptosis, while it had no effect on the Ca²⁺ increase. Taken together, our results suggest that a Ca²⁺ influx via TRPV1 is responsible for UVB irradiation-induced Nrf2 degradation and that modulation of the Ca²⁺-calmodulin-calcineurin-GSK3β-Nrf2-β-TrCP-Cullin-1 pathway may explain Ca²⁺ dependent Nrf2 degradation.

Melatonin induces reactive oxygen species generation and changes in glutathione levels and reduces viability in human pancreatic stellate cells

In this study, the effects of pharmacological concentrations of melatonin (1 μM-1 mM) on human pancreatic stellate cells (HPSCs) have been examined. Cell type-specific markers and expression of melatonin receptors were analyzed by western blot analysis. Changes in intracellular free Ca2+ concentration were followed by fluorimetric analysis of fura-2-loaded cells. Reduced glutathione (GSH) and oxidized glutathione (GSSG) levels were determined by fluorescence techniques. Production of reactive oxygen species (ROS) was monitored following 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate acetyl ester and MitoSOX™ Red-derived fluorescence. Cell viability was studied using the AlamarBlue® test. Cultured cells expressed markers typical of stellate cells. However, cell membrane receptors for melatonin could not be detected. Thapsigargin, bradykinin, or melatonin induced changes in intracellular free Ca2+ concentration. In the presence of the indole, a decrease in the GSH/GSSG ratio was observed that depended on the concentration of melatonin used. Furthermore, the indole evoked a concentration-dependent increase in ROS production in the mitochondria and in the cytosol. Finally, melatonin decreased HPSC viability in a time and concentration-dependent manner. We conclude that melatonin, at pharmacological concentrations, induces changes in the oxidative state of HPSC. This might regulate cellular viability and could not involve specific plasma membrane receptors.

The organophosphorus pesticide dimethoate decreases cell viability and induces changes in different biochemical parameters of rat pancreatic stellate cells

In the present study we employed cultured pancreatic stellate cells to study the effect of the organophosphorus insecticide dimethoate on pancreatic cell physiology. Esterase activity, cell viability, reactive oxygen species generation and Ca2+ mobilization were examined. Our results show that dimethoate (0.1, 1 and 10 μM) induced a concentration-dependent inhibition of cholinesterase enzymatic activity at all concentrations tested. A drop in carboxylesterase activity was noted in the presence of 10 μM dimethoate. In the presence of the pesticide a decrease in cell viability was detected. The clearer effect could be observed when the cells had been incubated during 96 h in the presence of dimethoate. The pesticide induced a slight but statistically significant increase in the production of reactive oxygen species in the mitochondria. Incubation of cells with dimethoate, in the presence of Ca2+ in the extracellular medium, led to a slow and progressive increase in [Ca2+]c towards an elevated value over the prestimulation level. A similar behavior was observed in the absence of extracellular Ca2+, indicating that dimethoate releases Ca2+ from the intracellular stores. Our results suggest that dimethoate might alter intracellular pathways that are critical for pancreatic physiology, creating a situation potentially leading to dysfunction in the exocrine pancreas.

Effects of anti-human T lymphocyte immune globulins in patients: new or old

Multiple studies demonstrated that anti‐human T lymphocyte immune globulins (ATG) can decrease the incidence of acute and chronic graft rejection in cell or organ transplants. However, further in‐depth study indicates that different subgroups may benefit from either different regimes or alteration of them. Studies among renal transplant patients indicate that low immunological risk patients may not gain the same amount of benefit and thus tilt the risk versus benefit consideration. This may hold true for low immunological risk patients receiving other organ transplants and would be worth further investigation. The recovery time of T cells and natural killer (NK) cells also bears consideration and the impact that it has on the severity and incidence of opportunistic infections closely correlated with the dosage of ATG. The use of lower doses of ATG in combination with other induction medications may offer a solution. The finding that ATG may lose efficacy in cases of multiple transplants or re‐transplants in the case of heart transplants may hold true for other transplantations. This may lead to reconsideration of which induction therapies would be most beneficial in the clinical setting. These studies on ATG done on different patient groups will naturally not be applicable to all, but the evidence accrued from them as a whole may offer us new and different perspectives on how to approach and potentially solve the clinical question of how to best reduce the mortality associated with chronic host‐versus‐graft disease.

Melatonin Prevents Mitochondrial Damage Induced by Doxorubicin in Mouse Fibroblasts Through Ampk-Ppar Gamma-Dependent Mechanisms

BACKGROUND Doxorubicin (brand name: Adriamycin®) is used to treat solid tissue cancer but it also affects noncancerous tissues. Its mechanism of cytotoxicity is probably related to increased oxidation, mitochondrial dysfunction, and apoptosis. Melatonin is reported to have antiapoptotic and antioxidative effects. The aim of this study was to determine whether melatonin would counteract in vitro cytotoxicity of doxorubicin in mouse fibroblasts and determine the pathway of its action against doxorubicin-induced apoptosis. MATERIAL AND METHODS We measured markers of apoptosis (cytochrome-c, mitochondrial membrane potential, and apoptotic cell number) and oxidative stress (total oxidant and antioxidant status) and calculated oxidant stress index in 4 groups of fibroblasts: controls, melatonin-treated, doxorubicin-treated, and fibroblasts concomittantly treated with a combination of melatonin and doxorubicin. RESULTS Melatonin given with doxorubicin succesfully countered apoptosis generated by doxorubicin alone, which points to its potential as a protective agent against cell death in doxorubicin chemotherapy. This also implies that patients should be receiving doxorubicin treatment when their physiological level of melatonin is at its highest, which is early in the morning. CONCLUSIONS This physiological level may not be high enough to overcome doxorubicin-induced oxidative stress, but adjuvant melatonin treatment may improve quality of life. Further research is needed to verify our findings.

Pancreatic stellate cell: physiologic role, role in fibrosis and cancer

PURPOSE OF REVIEW

Ever since the first descriptions of methods to isolate pancreatic stellate cells (PSCs) from rodent and human pancreas 17 years ago, rapid advances have been made in our understanding of the biology of these cells and their functions in health and disease. This review updates recent literature in the field, which indicates an increasingly complex role for the cells in normal pancreas, pancreatitis and pancreatic cancer.

RECENT FINDINGS

Work reported over the past 12 months includes improved methods of PSC immortalization, a role for PSCs in islet fibrosis, novel factors causing PSC activation as well as those inducing quiescence, and translational research aimed at inhibiting the facilitatory effects of PSCs on disease progression in chronic pancreatitis as well as pancreatic cancer.

SUMMARY

Improved understanding of the role of PSCs in pancreatic pathophysiology has prompted a focus on translational studies aimed at developing novel approaches to modulate PSC function in a bid to improve clinical outcomes of two major fibrotic diseases of the pancreas: chronic pancreatitis and pancreatic cancer.