Melatonin prevents apoptosis induced by UV-B treatment in U937 cell line

Long non-coding RNA SNHG17 may function as a competitive endogenous RNA in diffuse large B-cell lymphoma progression by sponging miR-34a-5p

We investigated the functional mechanism of long non-coding small nucleolar host gene 17 (SNHG17) in diffuse large B-cell lymphoma (DLBCL). lncRNAs related to the prognosis of patients with DLBCL were screened to analyze long non-coding small nucleolar host gene 17 (SNHG17) expression in DLBCL and normal tissues, and a nomogram established for predicting DLBCL prognosis. SNHG17 expression in B-cell lymphoma cells was detected using qPCR. The effects of SNHG17 with/without doxorubicin on the proliferation and apoptosis of DoHH2 and Daudi were detected. The effects of combined SNHG17 and doxorubicin were analyzed. The regulatory function of SNHG17 in DLBCL was investigated using a mouse tumor xenotransplantation model. RNA sequencing was used to analyze the signaling pathways involved in SNHG17 knockdown in B-cell lymphoma cell lines. The target relationships among SNHG17, microRNA, and downstream mRNA biomolecules were detected. A higher SNHG17 level predicted a lower survival rate. SNHG17 was highly expressed in DLBCL patient tissues and cell lines. We established a prognostic model containing SNHG17 expression, which could effectively predict the overall survival rate of DLBCL patients. SNHG17 knockdown inhibited the proliferation and induced the apoptosis of B-cell lymphoma cells, and the combination of SNHG17 and doxorubicin had a synergistic effect. SNHG17, miR-34a-5p, and ZESTE gene enhancer homolog 2 (EZH2) had common hypothetical binding sites, and the luciferase reporter assay verified that miR-34a-5p was the direct target of SNHG17, and EZH2 was the direct target of miR-34a-5p. The carcinogenic function of SNHG17 in the proliferation and apoptosis of DLBCL cells was partially reversed by a miR-34a-5p inhibitor. SNHG17 increases EZH2 levels by inhibiting miR-34a-5p. Our findings indicate SNHG17 as critical for promoting DLBCL progression by regulating the EZH2 signaling pathway and sponging miR-34a-5p. These findings provide a new prognostic marker and therapeutic target for the prognosis and treatment of DLBCL.

Melatonin and Autophagy in Aging-Related Neurodegenerative Diseases

With aging, the nervous system gradually undergoes degeneration. Increased oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction, and cell death are considered to be common pathophysiological mechanisms of various neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), organophosphate-induced delayed neuropathy (OPIDN), and amyotrophic lateral sclerosis (ALS). Autophagy is a cellular basic metabolic process that degrades the aggregated or misfolded proteins and abnormal organelles in cells. The abnormal regulation of neuronal autophagy is accompanied by the accumulation and deposition of irregular proteins, leading to changes in neuron homeostasis and neurodegeneration. Autophagy exhibits both a protective mechanism and a damage pathway related to programmed cell death. Because of its "double-edged sword", autophagy plays an important role in neurological damage and NDDs including AD, PD, HD, OPIDN, and ALS. Melatonin is a neuroendocrine hormone mainly synthesized in the pineal gland and exhibits a wide range of biological functions, such as sleep control, regulating circadian rhythm, immune enhancement, metabolism regulation, antioxidant, anti-aging, and anti-tumor effects. It can prevent cell death, reduce inflammation, block calcium channels, etc. In this review, we briefly discuss the neuroprotective role of melatonin against various NDDs via regulating autophagy, which could be a new field for future translational research and clinical studies to discover preventive or therapeutic agents for many NDDs.

Quercetin and Its Mixture Increase the Stress Resistance of Caenorhabditis elegans to UV-B

Ultraviolet B (UV-B, 280–320 nm) radiation causes complex molecular reactions in cells, including DNA damage, oxidative stress, and apoptosis. This study designed a mixture consisting of quercetin, luteolin and lycopene and used Caenorhabditis elegans as a model to study the resistance of these natural chemicals to UV-B. Specifically, we have confirmed that quercetin and its mixture can increase the resistance of Caenorhabditis elegans to UV-B through lifespan test, reactive oxygen species level assay, germ cell apoptosis test, embryonic lethal test and RT-qPCR experiments. The results show that quercetin and its mixture prolonged the lifespan of UV-B-irradiated Caenorhabditis elegans and reduced abnormal levels of reactive oxygen species, embryo death, and apoptosis induced by UV-B. The protective effect of quercetin and its mixture may be attributed to its down-regulation of HUS-1, CEP-1, EGL-1 and CED-13. Therefore, the results of this research could help the development of UV-B radiation protection agents.

Melatonin attenuates cadmium-induced ovulatory dysfunction by suppressing endoplasmic reticulum stress and cell apoptosis

BACKGROUND

Increasing evidence demonstrate that cadmium (Cd) has adverse effects on the mammalian reproductive system. However, the mechanisms underlying the effects of Cd on ovarian function and the strategies to reverse these effects have not been fully elucidated.

METHODS

In this study, 60 CD-1 mice were divided into four groups (control, melatonin, Cd, Cd with melatonin). During the treatment for 14 days, body weight was measured every 2 days. After the treatment, ovaries were isolated and weighted to observe the morphological and biological characteristics. Statistical analyses were performed using one-way ANOVA followed by Fisher's-multiple range test or chi-squared test, A P value < 0.05 indicated statistical significance.

RESULTS

We observed that Cd exposure induced ovulatory dysfunction, demonstrated by the reduced number of ovulated oocytes numbers in the Cd group. However, this endoplasmic reticulum (ER) pathway was activated in the Cd-exposed ovaries and the expression of GRP78, ATF4, CHOP, and p-JNK was upregulated, which was reversed by treatment with melatonin. Furthermore, we found that melatonin inhibited Cd-induced activation of cleaved caspase-3, restored the ratio of Bax/Bcl-2, and ultimately decreased the apoptosis of granular cells as detected by TUNEL staining.

CONCLUSION

Collectively, our findings reveal that melatonin attenuated Cd-induced ovulation dysfunction and cell apoptosis by inhibiting the activation of the ER pathway. Thus, melatonin can be a potential agent to protect mammalian ovaries against Cd toxicity.

Melatonin in macrophage biology: Current understanding and future perspectives

Melatonin is a ubiquitous hormone found in various organisms and highly affects the function of immune cells. In this review, we summarize the current understanding of the significance of melatonin in macrophage biology and the beneficial effects of melatonin in macrophage-associated diseases. Enzymes associated with synthesis of melatonin, as well as membrane receptors for melatonin, are found in macrophages. Indeed, melatonin influences the phenotype polarization of macrophages. Mechanistically, the roles of melatonin in macrophages are related to several cellular signaling pathways, such as NF-κB, STATs, and NLRP3/caspase-1. Notably, miRNAs (eg, miR-155/-34a/-23a), cellular metabolic pathways (eg, α-KG, HIF-1α, and ROS), and mitochondrial dynamics and mitophagy are also involved. Thus, melatonin modulates the development and progression of various macrophage-associated diseases, such as cancer and rheumatoid arthritis. This review provides a better understanding about the importance of melatonin in macrophage biology and macrophage-associated diseases.

The impact of environmental contamination on the generation of reactive oxygen and nitrogen species - Consequences for plants and humans

Environmental contaminants, such as heavy metals, nanomaterials, and pesticides, induce the formation of reactive oxygen and nitrogen species (RONS). Plants interact closely with the atmosphere, water, and soil, and consequently RONS intensely affect their biochemistry. For the past 30 years researchers have thoroughly examined the role of RONS in plant organisms and oxidative modifications to cellular components. Hydrogen peroxide, superoxide anion, nitrogen(II) oxide, and hydroxyl radicals have been found to take part in many metabolic pathways. In this review the various aspects of the oxidative stress induced by environmental contamination are described based on an analysis of literature. The review reinforces the contention that RONS play a dual role, that is, both a deleterious and a beneficial one, in plants. Environmental contamination affects human health, also, and so we have additionally described the impact of RONS on the coupled human - environment system.

AH6809 decreases production of inflammatory mediators by PGE2 - EP2 - cAMP signaling pathway in an experimentally induced pure cerebral concussion in rats

Increasing evidence suggests that PGE₂ metabolic pathway is involved in pathological changes of the secondary brain injury after traumatic brain injury. However, the underlying mechanisms, in particular, the correlation between various key enzymes and the brain injury, has remained to be fully explored. More specifically, it remains to be ascertained whether AH6809 (an EP2 receptor antagonist) would interfere with the downstream of the PGE₂, regulate the inflammatory mediators and improve neuronal damage in the hippocampus by PGE₂ - EP2 - cAMP signaling pathway. The expression and pathological changes of cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), microsomal prostaglandin-E synthase-1 (mPGES-1), E-prostanoid receptor 2 (EP2), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and inducible nitricoxide synthase (iNOS) in the CA1 area of hippocampus were evaluated by immunohistochemistry, Western blot and RT-PCR after pure cerebral concussion (PCC) induced by a metal pendulum closed brain injury in rats followed by AH6809 treatment. The morphology and number of neurons in CA1 region were analyzed by cresyl violet staining. The concentration of prostaglandin E₂ (PGE₂) and cyclic adenosine monophosphate (cAMP) was assayed by ELISA. Many neurons in hippocampal CA1 area appeared to undergo necrosis and the number of neurons was concomitantly reduced after PCC injury. With the passage of time, the protein and mRNA expression of various key enzymes including COX-1, COX-2 and mPGES-1, EP2 receptor, and inflammatory mediators including TNF-α, IL-1β and iNOS was increased; meanwhile, the concentration of PGE₂ and cAMP was enhanced. After PCC injury given AH6809 intervention, injury of neurons in hippocampal CA1 area was attenuated. The protein and mRNA expression of COX-1, COX-2, mPGES-1, EP2, TNF-α, IL-1β and iNOS was decreased, this was coupled with reduction of PGE₂ and cAMP. The results suggest that PGE₂ metabolic pathway is involved in secondary pathological changes of PCC. AH6809 improves the recovery of injured neurons in the hippocampal CA1 area and downregulates the inflammatory mediators by PGE₂ - EP2 - cAMP signaling pathway.

Protective effect of different antioxidant agents in UVB-irradiated keratinocytes

Skin cells can respond to UVB-induced damage either by tolerating it, or restoring it through antioxidant activation and DNA repair mechanisms or, ultimately, undergoing programmed cell death, when damage is massive. Nutritional factors, in particular, food antioxidants, have attracted much interest because of their potential use in new preventive, protective, and therapeutic strategies for chronic degenerative diseases, including skin inflammation and cancer. Some polyphenols, present in virgin olive oil, well tolerated by organism after oral administration, show a variety of pharmacological and clinical benefits such as antioxidant, anti-cancer, anti-inflammatory, and neuro-protective activities. Here, the protective effects of antioxidant compounds against UV-induced apoptosis have been described in HaCaT cell line. Human keratinocytes were pre-treated with antioxidants before UVB exposure and their effects have been evaluated by means of ultrastructural analyses. After UVB radiation, a known cell death trigger, typical apoptotic features, absent in control condition and in antioxidant alone-treated cells, appear. An evident numerical decrease of ultrastructural apoptotic patterns and TUNEL positive nuclei can be observed when natural antioxidants were supplied before cell death induction. These data have been confirmed by molecular investigation of caspase activity. In conclusion, this paper highlights antioxidant compound ability to prevent apoptotic cell death in human keratinocytes exposed to UVB, suggesting, for these molecules, a potential role in preventing skin damage.

Multiparameter analysis of apoptosis in puromycin-treated Saccharomyces cerevisiae

In Saccharomyces cerevisiae, a typical apoptotic phenotype is induced by some stress factors such as sugars, acetic acid, hydrogen peroxide, aspirin and age. Nevertheless, no data have been reported for apoptosis induced by puromycin, a damaging agent known to induce apoptosis in mammalian cells. We treated S. cerevisiae with puromycin to induce apoptosis and evaluated the percentage of dead cells by using Hoechst 33342 staining, transmission electron microscopy (TEM) and Annexin V flow cytometry (FC) analysis. Hoechst 33342 fluorescence images were processed to acquire parameters to use for multiparameter analysis [and perform a principal component analysis, (PCA)]. Cell viability was evaluated by Rhodamine 123 (Rh 123) and Acridine Orange microscope fluorescence staining. The results show puromycin-induced apoptosis in S. cerevisiae, and the PCA analysis indicated that the increasing percentage of apoptotic cells delineated a well-defined graph profile. The results were supported by TEM and FC. This study gives new insights into yeast apoptosis using puromycin as inducer agent, and PCA analysis may complement molecular analysis facilitating further studies to its detection.

Role of melatonin in traumatic brain injury and spinal cord injury

Brain and spinal cord are implicated in incidences of two of the most severe injuries of central nervous system (CNS). Traumatic brain injury (TBI) is a devastating neurological deficit involving primary and secondary injury cascades. The primary and secondary mechanisms include complex consequences of activation of proinflammatory cytokines, cerebral edema, upregulation of NF-κβ, disruption of blood-brain barrier (BBB), and oxidative stress. Spinal cord injury (SCI) includes primary and secondary injury cascades. Primary injury leads to secondary injury in which generation of free radicals and oxidative or nitrative damage play an important pathophysiological role. The indoleamine melatonin is a hormone secreted or synthesized by pineal gland in the brain which helps to regulate sleep and wake cycle. Melatonin has been shown to be a versatile hormone having antioxidative, antiapoptotic, neuroprotective, and anti-inflammatory properties. It has a special characteristic of crossing BBB. Melatonin has neuroprotective role in the injured part of the CNS after TBI and SCI. A number of studies have successfully shown its therapeutic value as a neuroprotective agent in the treatment of neurodegenerative diseases. Here in this review we have compiled the literature supporting consequences of CNS injuries, TBI and SCI, and the protective role of melatonin in it.

Honey flavonoids inhibit Candida albicans morphogenesis by affecting DNA behavior and mitochondrial function

AIM

Candida albicans is a pathogenic yeast, which forms a range of polarized and expanded cell shapes. We aimed to determine the correlation between honey extract (HFE) activity and changes in C. albicans cell cycle, morphology and subcellular organelles.

MATERIALS & METHODS

HFE anticandidal properties were investigated using flow cytometry and scanning electron microscopy.

RESULTS

Flow cytometry and scanning electron microscopy analyses indicated that HFE may inhibit the growth of the three phenotypes displayed by C. albicans and reduce infection by affecting membrane integrity. HFE affects hyphal transition by reducing the G0/G1 phase and increasing the G2/M phase. Conversely, yeast and pseudohyphae do not appear to be affected. Modifications of vacuolization and mitochondrial activity, during yeast-hypha transition establish the involvement of vacuole and mitochondria.

CONCLUSION

HFE improved mitochondrial functionality and reduced the vacuolization, modifying the branching process associated with virulence. It is hypothesized that HFE induces changes in cell cycle progress, membrane integrity, mitochondrial function and biogenesis.

Antioxidants in the prevention of UVB-induced keratynocyte apoptosis

Skin cells can respond to UVB-induced damage by counteracting it through antioxidant activation and DNA repair mechanisms or, when damage is massive by undergoing programmed cell death. Antioxidant factors, and, in particular, food compounds, have attracted much interest because of their potential use in new protective strategies for degenerative skin disorders. Melatonin, creatine and hydroxytyrosol show a variety of pharmacological and clinical benefits including anti-oxidant and anti-inflammatory activities. Here, the potential protective actions of antioxidant compounds against UVB-induced apoptosis were investigated in human keratinocytes. The cells were pre-treated with antioxidants before UVB exposure and their effect evaluated by means of ultrastructural and molecular analyses. After UVB radiation typical morphological apoptotic features and in situ DNA fragmentation after TUNEL reaction, appeared. A significant numerical decrease of apoptotic patterns could be observed when antioxidants were administrated before cell death induction. Moreover, both the intrinsic and extrinsic apoptotic pathways appeared activated after UVB radiation, and their down-regulation has been shown when antioxidants were added to cells before death induction. In conclusion, these compounds are able to prevent apoptotic cell death in human keratinocytes exposed to UVB, suggesting, for these molecules, an important role in preventing skin damage.

CCAR2 deficiency augments genotoxic stress-induced apoptosis in the presence of melatonin in non-small cell lung cancer cells

Melatonin exhibits oncostatic activity in several cancers but does not lead to cytotoxicity in estrogen receptor (ER)-negative non-small cell lung cancers (NSCLCs). In an effort to overcome the melatonin resistance of these cancers, we investigated whether cell cycle and apoptosis regulator 2 (CCAR2) depletion would promote apoptosis following genotoxic stress in melatonin-resistant cancer cells. Ordinarily, the NSCLC cell lines A549 and A427 did not undergo cell death following melatonin treatment for short period. These cell lines were irradiated with UV, a source of genotoxic damage, to trigger apoptotic signaling. Treatment with melatonin prior to irradiation did not produce any significant change in apoptosis. By contrast, in CCAR2-deficient cells, melatonin treatment increased apoptosis induced by genotoxic stress; this effect was dependent on the dose of melatonin. The increase in apoptosis in CCAR2-deficient cells was not dependent on SIRT1. The results indicate that CCAR2 is critical for maintaining cell survival in the presence of melatonin under genotoxic stress. Furthermore, CCAR2 is overexpressed in NSCLC; therefore, melatonin could be used as a potential supplement to classical anticancer drugs in therapies against CCAR2-deficient cancers.

Melatonin prevents chemical-induced haemopoietic cell death

Melatonin (MEL), a methoxyindole synthesized by the pineal gland, is a powerful antioxidant in tissues as well as within cells, with a fundamental role in ameliorating homeostasis in a number of specific pathologies. It acts both as a direct radical scavenger and by stimulating production/activity of intracellular antioxidant enzymes. In this work, some chemical triggers, with different mechanisms of action, have been chosen to induce cell death in U937 hematopoietic cell line. Cells were pre-treated with 100 µM MEL and then exposed to hydrogen peroxide or staurosporine. Morphological analyses, TUNEL reaction and Orange/PI double staining have been used to recognize ultrastructural apoptotic patterns and to evaluate DNA behavior. Chemical damage and potential MEL anti-apoptotic effects were quantified by means of Tali® Image-Based Cytometer, able to monitor cell viability and apoptotic events. After trigger exposure, chromatin condensation, micronuclei formation and DNA fragmentation have been observed, all suggesting apoptotic cell death. These events underwent a statistically significant decrease in samples pre-treated with MEL. After caspase inhibition and subsequent assessment of cell viability, we demonstrated that apoptosis occurs, at least in part, through the mitochondrial pathway and that MEL interacts at this level to rescue U937 cells from death.

Melatonin's protective effect against UV radiation: a systematic review of clinical and experimental studies

BACKGROUND

Ultraviolet (UV) radiation is the main etiologic factor for skin cancer. The endogenous hormone melatonin has been proposed to have protective effects against sunlight.

AIM

The aim of this review was to evaluate melatonin's protective effects against UV radiation and to clarify the cellular mechanisms behind this effect.

METHOD

Medline, Embase and Cinahl were searched up to January 2013 to identify studies evaluating melatonin's protective effect against UV radiation (UVR)-induced skin erythema in humans and damage on a cellular level.

RESULTS

Four human studies have investigated melatonin's protective effect on UVR-induced skin damage. Melatonin was shown to have protective effects when applied before UVR, but no effect if applied after exposure. A total of 16 experimental studies evaluated melatonin's protective effect against UVR-induced damage to cellular structures and pathways.

DISCUSSION/CONCLUSION

The protection against UVR-induced skin damage was conducted by melatonin acting directly as an antioxidant, and indirectly by regulating gene expression and inducing a DNA stabilizing effect. As these results were obtained using artificial UVR and without investigating possible side effects, studies using natural sunlight and evaluating possible side effects of topical melatonin administration are warranted.

Growth hormone plus resistance exercise attenuate structural changes in rat myotendinous junctions resulting from chronic unloading

Myotendinous junctions (MTJs) are specialized sites on the muscle surface where forces generated by myofibrils are transmitted across the sarcolemma to the extracellular matrix. At the ultrastructural level, the interface between the sarcolemma and extracellular matrix is highly folded and interdigitated at these junctions. In this study, the effect of exercise and growth hormone (GH) treatments on the changes in MTJ structure that occur during muscle unloading, has been analyzed. Twenty hypophysectomized rats were assigned randomly to one of five groups: ambulatory control, hindlimb unloaded, hindlimb unloaded plus exercise (3 daily bouts of 10 climbs up a ladder with 50% body wt attached to the tail), hindlimb unloaded plus GH (2 daily injections of 1 mg/kg body wt, i.p.), and hindlimb unloaded plus exercise plus GH. MTJs of the plantaris muscle were analyzed by electron microscopy and the contact between muscle and tendon was evaluated using an IL/B ratio, where B is the base and IL is the interface length of MTJ's digit-like processes. After 10 days of unloading, the mean IL/B ratio was significantly lower in unloaded (3.92), unloaded plus exercise (4.18), and unloaded plus GH (5.25) groups than in the ambulatory control (6.39) group. On the opposite, the mean IL/B ratio in the group treated with both exercise and GH (7.3) was similar to control. These findings indicate that the interaction between exercise and GH treatments attenuates the changes in MTJ structure that result from chronic unloading and thus can be used as a countermeasure to these adaptations.

The role of melatonin in the cells of the innate immunity: a review

Melatonin is the major secretory product synthesized and secreted by the pineal gland and shows both a wide distribution within phylogenetically distant organisms from bacteria to humans and a great functional versatility. In recent years, a considerable amount of experimental evidence has accumulated showing a relationship between the nervous, endocrine, and immune systems. The molecular basis of the communication between these systems is the use of a common chemical language. In this framework, currently melatonin is considered one of the members of the neuroendocrine-immunological network. A number of in vivo and in vitro studies have documented that melatonin plays a fundamental role in neuroimmunomodulation. Based on the information published, it is clear that the majority of the present data in the literature relate to lymphocytes; thus, they have been rather thoroughly investigated, and several reviews have been published related to the mechanisms of action and the effects of melatonin on lymphocytes. However, few studies concerning the effects of melatonin on cells belonging to the innate immunity have been reported. Innate immunity provides the early line of defense against microbes and consists of both cellular and biochemical mechanisms. In this review, we have focused on the role of melatonin in the innate immunity. More specifically, we summarize the effects and action mechanisms of melatonin in the different cells that belong to or participate in the innate immunity, such as monocytes-macrophages, dendritic cells, neutrophils, eosinophils, basophils, mast cells, and natural killer cells.

Apoptosis of THP-1 macrophages induced by protoporphyrin IX-mediated sonodynamic therapy

Background

Sonodynamic therapy (SDT) was developed as a localized ultrasound-activated cytotoxic therapy for cancer. The ability of SDT to destroy target tissues selectively is especially appealing for atherosclerotic plaque, in which selective accumulation of the sonosensitizer, protoporphyrin IX (PpIX), had been demonstrated. Here we investigate the effects of PpIX-mediated SDT on macrophages, which are the main culprit in progression of atherosclerosis.

Methods and results

Cultured THP-1 derived macrophages were incubated with PpIX. Fluorescence microscopy showed that the intracellular PpIX concentration increased with the concentration of PpIX in the incubation medium. MTT assay demonstrated that SDT with PpIX significantly decreased cell viability, and this effect increased with duration of ultrasound exposure and PpIX concentration. PpIX-mediated SDT induced both apoptosis and necrosis, and the maximum apoptosis to necrosis ratio was obtained after SDT with 20 μg/mL PpIX and five minutes of sonication. Production of intracellular singlet oxygen and secondary disruption of the cytoskeleton were also observed after SDT with PpIX.

Conclusion

PpIX-mediated SDT had apoptotic effects on THP-1 macrophages via generation of intracellular singlet oxygen and disruption of the cytoskeleton. PpIX-mediated SDT may be a potential treatment to attenuate progression of atherosclerotic plaque.

Ultraviolet B (UVB) irradiation-induced apoptosis in various cell lineages in vitro

Ultraviolet B (UVB) radiation acts as a strong apoptotic trigger in many cell types, in tumor and normal cells. Several studies have demonstrated that UVB-induced cell death occurs through the generation of reactive oxygen species. The consequent oxidative stress includes the impairment of cellular antioxidants, the induction of DNA damage and the occurrence of apoptosis. In this review, we investigated UVB apoptotic action in various cell models by using ultrastructural, molecular and cytofluorimetric techniques. Myeloid leukemia HL-60, T-lymphoblastoid Molt-4 and myelomonocytic U937 human cells, generally affected by apoptotic stimuli, were studied. Human chondrocytes and C2C12 skeletal muscle cells, known to be more resistant to damage, were also considered. All of them, when exposed to UVB radiation, revealed a number of characteristic apoptotic markers. Membrane blebbing, cytoplasm shrinkage and chromatin condensation were detected by means of electron microscopy. DNA cleavage, investigated by using agarose gel electrophoresis and TUNEL reaction, was observed in suspended cells. Differently, in chondrocytes and in skeletal muscle cells, oligonucleosomic DNA fragmentation did not appear, even if a certain TUNEL positivity was detected. These findings demonstrate that UVB radiation appears to be an ideal tool to study the apoptotic behavior.

Melatonin alleviates cadmium-induced cellular stress and germ cell apoptosis in testes

Increasing evidence demonstrates that melatonin has an anti-apoptotic effect in somatic cells. However, whether melatonin can protect against germ cell apoptosis remains obscure. Cadmium (Cd) is a testicular toxicant and induces germ cell apoptosis. In this study, we investigated the effects of melatonin on Cd-evoked germ cell apoptosis in testes. Male ICR mice were intraperitoneally (i.p.) injected with melatonin (5 mg/kg) every 8 hr, beginning at 8 hr before CdCl(2) (2.0 mg/kg, i.p.). As expected, acute Cd exposure resulted in germ cell apoptosis in testes, as determined by terminal dUTP nick-end labeling (TUNEL) staining. Melatonin significantly alleviated Cd-induced testicular germ cell apoptosis. An additional experiment showed that spliced form of XBP-1, the target of the IRE-1 pathway, was significantly increased in testes of mice injected with CdCl(2). GRP78, an endoplasmic reticulum (ER) chaperone, and CHOP, a downstream target of the PERK pathway, were upregulated in testes of Cd-treated mice. In addition, acute Cd exposure significantly increased testicular eIF2α and JNK phosphorylation, indicating that the unfolded protein response (UPR) pathway was activated by CdCl(2). Interestingly, melatonin almost completely inhibited Cd-induced ER stress and the UPR in testes. In addition, melatonin obviously attenuated Cd-induced heme oxygenase (HO)-1 expression and protein nitration in testes. Taken together, these results suggest that melatonin alleviates Cd-induced cellular stress and germ cell apoptosis in testes. Melatonin may be useful as pharmacological agents to protect against Cd-induced testicular toxicity.

Effects of melatonin on the proliferation and differentiation of rat adipose-derived stem cells

Background:

Osteogenesis driven by adipose-derived stem cells (ADSCs) is regulated by physiological and pathological factors. Accumulating evidence from in vitro and in vivo experiments suggests that melatonin may have an influence on bone formation. However, little is known about the effects of melatonin on osteogenesis, which thus remains to be elucidated. This study was performed to determine whether melatonin at physiological concentrations (0.01-10 nM) could affect the in vitro proliferation and osteogenic differentiation of rat ADSCs.

Materials and Methods:

ADSCs were isolated from the fat of adult rats. After cell expansion in culture media and through three passages, osteogenesis was induced in a monolayer culture using osteogenic medium with or without melatonin at physiological concentrations (0.01-10 nM). After four weeks, the cultures were examined for mineralization by Alizarin Red S and von Kossa staining and for alkaline phosphatase (ALP) activity using an ALP kit. Cell viability and apoptosis were also assayed by 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTT) assay and flow cytometry, respectively.

Results:

The results indicated that at physiological concentrations, melatonin suppressed proliferation and differentiation of ADSCs. These data indicate that ADSCs exposed to melatonin, had a lower ALP activity in contrast to the cells exposed to osteogenic medium alone. Similarly, mineral deposition (calcium level) also decreased in the presence of melatonin. Flow cytometry confirmed that cell growth had decreased and that the numbers of apoptotic cells had increased.

Conclusion:

These results suggest that the physiological concentration of melatonin has a negative effect on ADSC osteogenesis.

Protective effect of melatonin on oxaliplatin-induced apoptosis through sustained Mcl-1 expression and anti-oxidant action in renal carcinoma Caki cells

Melatonin is an indolamine initially found to be produced in the pineal gland but now known to be synthesized in a variety of other tissues as well. The mechanisms whereby melatonin regulates the apoptotic program remain only partially understood. Anti-/pro-apoptotic effects of exogenous melatonin on various stimuli-mediated apoptosis were investigated in this report. We investigated the combined effect of melatonin and death receptor-mediated ligands (TNF-α, TRAIL, and anti-Fas antibody) or endoplasmic reticulum (ER) stress-inducing agents (thapsigargin, brefeldin A, and tunicamycin) on apoptosis of cancer cells. Death receptor- or ER stress-induced apoptosis was not significantly influenced by melatonin treatment. However, pretreatment with melatonin significantly inhibited DNA damage-induced apoptosis and glutathione (GSH) depletion, suggesting the reactive oxygen species mediate oxaliplatin/etoposide-induced apoptosis. Interestingly, we also found the involvement of myeloid cell leukemia-1 (Mcl-1) downregulation in oxaliplatin-induced apoptosis; thus, pretreatment with melatonin inhibited Mcl-1 downregulation, and ectopic expression of Mcl-1 attenuated oxaliplatin-induced apoptosis. Taken together, the results demonstrate that melatonin attenuates oxaliplatin-induced apoptosis in cancer cells by inhibition of GSH depletion and Mcl-1 downregulation.

Flow cytometric profiles, biomolecular and morphological aspects of transfixed leukocytes and red cells

BACKGROUND

We evaluated the effects of the TransFix(TM) short-term stabilization technique on leukocyte subpopulations in both optimal and adverse storage temperatures and on different cellular concentrations. Particularly, we analyzed DNA cell content and membrane structure also for erythrocytes using a multiparametric approach.

METHODS

We studied biomolecular and morphological aspects of transfixed cells, by means of SEM, TEM, Western blotting, and by flow cytometry (FC). Furthermore, FC, Tunel, and electrophoresis were applied to evaluate DNA behavior.

RESULTS

We confirm preservation of scatter characteristics and immunophenotyping, extending such evaluations to cells stored in suboptimal conditions (25 degrees C and 37 degrees C) and in high density. Data demonstrate for lymphomonocytic cells an optimal conservation, slightly decreasing at higher temperatures for both 1/5 and 1/10 ratio (TransFix/sample), with enhanced autofluorescence. Eosinophils, basophils, and neutrophils are shown to preserve differently over time. The three different cellular concentrations evaluated (30,000-120,000 cell/microl) demonstrate substantial stability in FI values. Furthermore DNA content analysis attests the absence of any apoptotic pattern. Transfixed red cell protein profile as well as their morphological features appears almost unaltered.

CONCLUSIONS

Cytometric performance is suboptimal in aged unfixed specimens because of apoptosis that affects light scatter properties. Our findings highlight that lymphomonocytic cells are well stabilized even at suboptimal temperature and cell density. TransFix is able to abolish any apoptotic features and acts as an optimal blood preservative for appropriate preanalytical stabilization.

Melatonin signaling and cell protection function

Besides its well-known regulatory role on circadian rhythm, the pineal gland hormone melatonin has other biological functions and a distinct metabolism in various cell types and peripheral tissues. In different tissues and organs, melatonin has been described to act as a paracrine and also as an intracrine and autocrine agent with overall homeostatic functions and pleiotropic effects that include cell protection and prosurvival factor. These latter effects, documented in a number of in vitro and in vivo studies, are sustained through both receptor-dependent and -independent mechanisms that control detoxification and stress response genes, thus conferring protection against a number of xenobiotics and endobiotics produced by acute and chronic noxious stimuli. Redox-sensitive components are included in the cell protection signaling of melatonin and in the resulting transcriptional response that involves the control of NF-κB, AP-1, and Nrf2. By these pathways, melatonin stimulates the expression of antioxidant and detoxification genes, acting in turn as a glutathione system enhancer. A further and converging mechanism of cell protection by this indoleamine described in different models seems to lie in the control of damage and signaling function of mitochondria that involves decreased production of reactive oxygen species and activation of the antiapoptotic and redox-sensitive element Bcl2. Recent evidence suggests that upstream components in this mitochondrial route include the calmodulin pathway with its central role in melatonin signaling and the survival-promoting component of MAPKs, ERK1/2. In this review article, we will discuss these and other molecular aspects of melatonin signaling relevant to cell protection and survival mechanisms.

Melatonin reduces apoptosis induced by calcium signaling in human leukocytes: Evidence for the involvement of mitochondria and Bax activation

We have evaluated the effect of melatonin on apoptosis evoked by increases in [Ca(2+)]( c ) in human leukocytes. Our results show that treatment of neutrophils with the calcium mobilizing agonist FMLP or the specific inhibitor of calcium reuptake thapsigargin induced a transient increase in [Ca(2+)]( c ). Our results also show that FMLP and thapsigargin increased caspase-9 and -3 activities and the active forms of both caspases. The effect of FMLP and thapsigargin on caspase activation was time-dependent. Similar results were obtained when lymphocytes were stimulated with thapsigargin. This stimulatory effect was accompanied by induction of mPTP, activation of the proapoptotic protein Bax and release of cytochrome c. However, when leukocytes were pretreated with melatonin, all of the apoptotic features indicated above were significantly reversed. Our results suggest that melatonin reduces caspase-9 and -3 activities induced by increases in [Ca(2+)]( c ) in human leukocytes, which are produced through the inhibition of both mPTP and Bax activation.

Apoptotic DNA fragmentation can be revealed in situ: an ultrastructural approach

A common pattern of apoptotic death is DNA cleavage, initially producing large fragments (50 kbp), followed by the production of nucleosomic/oligonucleosomic fragments. Nevertheless, apoptosis without DNA fragmentation, at least of the nucleosomic type, has been reported. To investigate the spatial relationship between DNA cleavage and chromatin condensation, we applied the TUNEL technique to the ultrastructural analysis of apoptotic cells. A modified method, utilizing a gold-conjugated antidigoxigenin antibody, was carried out on U937 versus Molt-4 cells, both exposed to UVB radiation or staurosporine treatment. Gold particle density in the different domains of apoptotic cells was evaluated by a four-way ANOVA test. Gold labelling was more strongly localised in condensed chromatin than in the diffuse chromatin. U937 cells, which evidenced in vitro oligonucleosomic fragmentation after both UVB and staurosporine treatments, revealed a significantly higher gold particle density, when compared with Molt-4, which did not show, on the other hand, oligonucleosomic cleavage even in the presence of < or = 50 kbp cleavage. Thus, a correlation between DNA fragment sizes and gold particle density appears. TUNEL applied to electron microscopy is an effective approach to study the relationship between apoptotic chromatin condensation and DNA cleavage. Both these events indeed appear in the apoptotic nucleus, but their reciprocal correlation is still greatly unknown. Microsc. Res. Tech. 2009. (c) 2009 Wiley-Liss, Inc.

Melatonin exerts differential actions on X-ray radiation-induced apoptosis in normal mice splenocytes and Jurkat leukemia cells

The ability of melatonin as a potent antioxidant was used as a rationale for testing its antiapoptotic ability in normal cells. Recently, melatonin was shown to possess proapoptotic action by increasing reactive oxygen species in certain cancer cells. The modification of radiation-induced apoptosis by melatonin and the expression of apoptosis-associated upstream regulators were studied in normal mice splenocytes and Jurkat T leukemia cells. C57BL/6 mice were exposed to a single whole body X-ray radiation dose of 2 Gy with or without 250 mg/kg melatonin pretreatment. The Jurkat cells were divided into four groups of control, 1 mm melatonin alone, 4 Gy irradiation-only and melatonin pretreatment before irradiation. The highest level of apoptosis in the normal splenic white pulp was detected by TUNEL assay at 8 hr after irradiation. At this time, the apoptotic index of irradiation-only and melatonin pretreatment groups were 35.6% and 20.7%, respectively. This reduced apoptosis by melatonin was associated with the increase of Bcl-2 expression and a reduction of Bax/Bcl-2 ratio through a relative decrease of p53 mRNA and protein. In the Jurkat cells treated with a combination of melatonin and radiation, both Annexin V-FITC(+)/PI(-) and Annexin V-FITC(+) cells were increased at 48 hr after irradiation when compared with irradiation-only or melatonin alone. The expressions of p53 between groups were well correlated with the results of Annexin V binding. The irradiation or melatonin did not influence the JNK1 expression in Jurkat cells. The present results suggest that melatonin enhances radiation-induced apoptosis in Jurkat leukemia cells, while reducing radiation-induced apoptosis in normal mice splenocytes. These differential effects on radiation-induced apoptosis by melatonin might involve the regulation of p53 expression.

Melatonin induces mitochondrial-mediated apoptosis in human myeloid HL-60 cells

The role of melatonin in the mediation of apoptotic events has recently gained attention, especially after recent studies have reported that melatonin exerts antiapoptotic actions in normal cells but may activate proapoptotic pathways in some tumor cells. Here, we have evaluated the effect of melatonin on apoptosis in the human leukemia cell line HL-60. Melatonin treatment (1 mm) induced a significant increase in caspase-3 and -9 activities. The effect of melatonin on the activation of caspases was time dependent, reaching a maximum after 12 hr of stimulation, and then decreasing to a minimum after 72 hr. Treatment with melatonin also evoked mitochondrial membrane depolarization and permeability transition pore induction, which caused loss of mitochondrial staining by calcein, and increased cell death by apoptosis/necrosis as demonstrated by propidium iodide positive-staining of cells after 72 hr of stimulation. In addition, the exposure of cells to melatonin resulted in an activation and association of the proapoptotic proteins Bax and Bid, as well as promoting detectable increases in the expression of both proteins. We conclude that melatonin has proapoptotic and/or oncostatic effects in the human myeloid cell line HL-60.

ERK MAPK activation mediates the antiapoptotic signaling of melatonin in UVB-stressed U937 cells

The pineal gland hormone melatonin has been recently described to downregulate the intrinsic (or damage-induced) pathway of apoptosis in human leukocytes. These properties appear to depend on a specific mitochondrial signaling of melatonin which is associated with a lower generation of reactive oxygen species and a better control of redox-sensitive components such as the antiapoptotic protein Bcl-2. Other elements upstream in this signaling are expected to contribute regulatory roles that remain unexplored. The aim of this study was to investigate whether the extracellular signal-regulated kinase (ERK), which controls the balance between survival and death-promoting genes throughout the MAPK pathway, is involved in the antiapoptotic signaling of melatonin. Human monocytic U937 cells irradiated with UVB light were used as a model of stress-induced apoptosis. In this model we found that pharmacological concentrations of melatonin (1 mM) were able to decrease superoxide anion production, mitochondrial damage, and caspase-dependent apoptosis by improved Bcl-2 levels and decreased Cyt c release in the cytoplasm. Moreover, melatonin increased the phosphorylative activation of ERK 1/2 independently from the presence of UVB stress, and decreased the UVB-mediated activation of the stress kinases p38 MAPK and JNK. The ERK 1/2 inhibitor PD98059, but not the p38 MAPK inhibitor SB203580, abolished to different extents the effects that melatonin had on the UVB-induced ROS generation, mitochondrial dysfunction, and apoptosis. Using these inhibitors, a cross-talk effect between stress and survival-promoting kinases was tentatively identified, and confirmed the hierarchical role of ERK MAPK phosphorylation in the signaling of melatonin. In conclusion, melatonin sustains the activation of the survival-promoting pathway ERK MAPK which is required to antagonize UVB-induced apoptosis of U937 cells. This kinase mediates also the antioxidant and mitochondrial protection effects of this hormonal substance that may find therapeutic applications in inflammatory and immune diseases associated with leukocyte oxidative stress and accelerated apoptosis.

Immunotoxicity of carbon black nanoparticles to blue mussel hemocytes

The potential for human and ecological toxicity associated with nanomaterials is a growing area of investigation. In mammalian cells, nanoparticles have been shown to induce inflammation and oxidative stress, and changes in cell signalling and gene expression. As the nanotechnology industries increase production, nanoscale products and by products will enter the aquatic environment, posing a possible threat to aquatic organisms. In particular, filter-feeding organisms may represent a unique target group for nanoparticle toxicology. In this work, the effects of commercial nanosized carbon black (NCB) on the immune cells, the hemocytes, of the bivalve mollusc Mytilus, and the possible mechanisms involved were investigated. The results demonstrate that NCB (1, 5, and 10 microg/ml), did not induce significant lysosomal membrane destabilization, as evaluated by the NR retention time assay. A concentration-dependent uptake of NCB by hemocytes was observed and it was associated by a rapid increase in extracellular lysozyme release, extracellular oxyradical production, and nitric oxide (NO) release. Moreover, at the highest concentration tested, NCB induced significant changes in mitochondrial parameters (decrease mitochondrial mass/number and membrane potential), as evaluated by flow cytometry. The effects of NCB were mediated by rapid activation of the stress-activated MAPKs (Mitogen Activated Protein Kinases) p38 and JNKs, that play a key role in immune and inflammatory responses. The results demonstrate that in mussel hemocytes like in mammalian cells NCB exposure can induce inflammatory processes, and indicate that bivalve immunocytes can represent a suitable model for investigating the effects and modes of action of nanoparticles in the cells of aquatic invertebrates.

Melatonin uptake in prostate cancer cells: intracellular transport versus simple passive diffusion

Melatonin, an indole mainly synthesized in the pineal gland during the dark phase, plays a role as an endogenous antioxidant and an anticancer agent in many tumors. Melatonin, at pharmacological concentrations, inhibits cell growth and induces neuroendocrine differentiation in prostate cancer cells. Classically it has been considered that melatonin enters freely into most of cells by passive diffusion through the cell membrane; however, there are few studies examining how melatonin is taken up by cancer cells. The aim of the present paper was to study the uptake of melatonin into human androgen-dependent LNCaP and androgen-independent PC-3 prostate cancer cells. Increased concentrations of melatonin induced a rapid and transitory rise in intracellular melatonin content in both cell types, with a peak of maximal content at 6 hr after melatonin addition, following a rhythmic uptake; melatonin was found in both cytoplasm and nuclear fractions. Inhibition of protein or RNA synthesis partially blocked melatonin uptake in both cell lines. Interestingly, melatonin pulse incubation led to a higher uptake after four cycles of pulse incubation. Neither extracellular Ca(2+)/K(+) alterations nor the presence of bovine serum albumin or charcoal-stripped serum modified the profile of melatonin uptake. On the contrary, chemical binding of melatonin to BSA totally prevented melatonin from entering into cells. The present data support the hypothesis that a facilitated diffusion or an active process rather than simple passive diffusion through the cell membrane is the major mechanism in melatonin uptake by prostate cancer cells and it accounts for its intracellular concentration (350 nM-3.3 microM), which is related to its anti-tumor actions.

Melatonin antagonizes the intrinsic pathway of apoptosis via mitochondrial targeting of Bcl-2

We have recently shown that melatonin antagonizes damage-induced apoptosis by interaction with the MT-1/MT-2 plasma membrane receptors. Here, we show that melatonin interferes with the intrinsic pathway of apoptosis at the mitochondrial level. In response to an apoptogenic stimulus, melatonin allows mitochondrial translocation of the pro-apoptotic protein Bax, but it impairs its activation/dimerization The downstream apoptotic events, i.e. cytochrome c release, caspase 9 and 3 activation and nuclear vesiculation are equally impaired, indicating that melatonin interferes with Bax activation within mitochondria. Interestingly, we found that melatonin induces a strong re-localization of Bcl-2, the main Bax antagonist to mitochondria, suggesting that Bax activation may in fact be antagonized by Bcl-2 at the mitochondrial level. Indeed, we inhibit the melatonin anti-apoptotic effect (i) by silencing Bcl-2 with small interfering RNAs, or with small-molecular inhibitors targeted at the BH3 binding pocket in Bcl-2 (i.e. the one interacting with Bax); and (ii) by inhibiting melatonin-induced Bcl-2 mitochondrial re-localization with the MT1/MT2 receptor antagonist luzindole. This evidence provides a mechanism that may explain how melatonin through interaction with the MT1/MT2 receptors, elicits a pathway that interferes with the Bcl-2 family, thus modulating the cell life/death balance.

Evidence supporting antioxidant action of adipose-derived stem cells: protection of human dermal fibroblasts from oxidative stress

BACKGROUND

Mesenchymal stem cells within the stromal-vascular fraction of subcutaneous adipose tissue, adipose-derived stem cells (ADSCs), produced soluble factors and they exhibit diverse pharmacological effects in skin biology.

OBJECTIVE

The present study examines the protective effect of ADSCs for human dermal fibroblasts (HDFs) through anti-oxidation in a tert-butyl hydroperoxide (tbOOH) induced oxidative injury model.

METHODS AND RESULTS

The conditioned medium of ADSCs (ADSC-CM) was harvested and tested for antioxidant action. ADSC-CM had an antioxidant effect as potent as 100 microM ascorbic acid and various antioxidant proteins were detected in ADSC-CM by proteomic analysis. Morphological change and cell survival assay revealed that incubation with ADSC-CM aided HDFs to resist free radicals induced by tbOOH. In addition, activities of superoxide dismutase and glutathione peroxidase were enhanced in the ADSC-CM treated HDFs which confirmed the study hypothesis that ADSCs protect HDFs through antioxidant action. In a cell cycle analysis, ADSC-CM treatment reversed the apoptotic cell death induced by tbOOH and caused a decrease of sub-G1 cells with respect to untreated cells. The anti-apoptotic effect of ADSC-CM was also reproduced by caspase-3 activity assay.

CONCLUSION

These results suggest that ADSCs have potent antioxidant activity and protect HDFs from oxidative injury by decreasing apoptotic cells. Therefore, ADSCs and ADSC-CM are good candidates for control and prevention of skin damage from free radicals in various skin conditions.

Melatonin is able to reduce the apoptotic liver changes induced by aging via inhibition of the intrinsic pathway of apoptosis

We examined the effect of daily melatonin supplementation on liver apoptosis induced by aging in rats. Young (3-month-old) and aged (24-month-old) Wistar rats were supplemented daily with melatonin in their drinking water (20 mg/L) for 4 weeks. Aged rats showed increases in the liver concentration of thiobarbituric acid-reactive substances and in the oxidized/reduced glutathione ratio. These increases were accompanied by apoptotic ultrastructural alterations and increases in cytochrome c mitochondrial release, Bax to Bcl-2 relative expression, and activity of caspase-3. No significant changes were observed in Fas-ligand (Fas-L) expression and caspase-8 activity. Melatonin administration was able to abrogate changes detected in aged rats. Data suggest that liver apoptotic cell death is induced by reactive oxygen species, via the intrinsic signalling pathway, and that the antiapoptotic action provided by melatonin is related to its antioxidant effect, with reduction of cytochrome c release by the modulation of Bcl-2 and Bax genes.

Melatonin attenuates lipopolysaccharide (LPS)-induced apoptotic liver damage in d-galactosamine-sensitized mice

D-Galactosamine (GalN) depletes UTP primarily in liver, resulting in decreased RNA synthesis in hepatocytes. When given together with a sublethal dose of lipopolysaccharide (LPS), GalN highly sensitizes animals to produce apoptotic liver injury with severe hepatic congestion, resulting in rapid death. Melatonin is a cytokine modulator, antioxidant and anti-apoptotic agent. In the present study, we investigated the effect of melatonin on LPS-induced apoptotic liver damage in GalN-sensitized mice. Female CD-1 mice were intraperitoneally (i.p.) injected with melatonin (5.0mg/kg) 30min before GalN/LPS (700mg10microg/kg, i.p.), another two doses of melatonin (2.5mg/kg, i.p.) being administered 1 and 2h after GalN/LPS. Results showed that serum alanine aminotransferase (ALT) activities were markedly increased 8h after GalN/LPS treatment, massive hemorrhage being observed in histological sections of liver from GalN/LPS-treated mice. Melatonin significantly attenuated GalN/LPS-induced elevation of serum ALT. In parallel, melatonin distinctly improved GalN/LPS-induced congestion. Additional experiment showed that melatonin significantly attenuated GalN/LPS-induced hepatic apoptosis, measured by inhibition of caspase-3 activities and attenuation of DNA laddering. Furthermore, melatonin markedly increased hepatic Se-dependent glutathione peroxidase (GSH-Px) and glutathione reductase (GSH-Rd) activities and attenuated hepatic glutathione (GSH) depletion in GalN/LPS-treated mice. Increases in serum tumor necrosis factor alpha (TNF-alpha), which were observed in GalN/LPS-treated mice, were significantly reduced by melatonin. However, melatonin had no effect on LPS-evoked nitric oxide production in GalN-sensitized mice. Taken together, these results indicate that melatonin protected against LPS-induced liver damage in GalN-sensitized mice through its strong ROS-scavenging, antiinflammatory and antiapoptotic effects.

Enzyme-assisted photosensitization with rose Bengal acetate induces structural and functional alteration of mitochondria in HeLa cells

Rose Bengal acetate (RB-Ac) can be used as a fluorogenic substrate for photosensitization of cells both in vivo and in vitro: once inside the cells, RB-Ac is converted into photoactive rose Bengal (RB) molecules which redistribute dynamically in the cytoplasm and, upon irradiation by visible green light, can damage organelles such as the endoplasmic reticulum, the Golgi apparatus, and the cytoskeleton. Recently, evidence has been provided that mitochondria may also be affected. The aims of the present study were to describe RB-induced photodamage of mitochondria in single HeLa cells and to define, on a quantitative basis, the effects of photosensitization on their morphofunctional features. HeLa cell cultures were exposed to 10(-5) M RB-Ac for 60 min and then irradiated with a light emitting diode at 530 nm (total light dose, 1.6 J/cm2). After irradiation, the cells were transferred to a drug-free complete medium and allowed to grow for 24-72 h. Using conventional and confocal fluorescence microscopy, transmission electron microscopy, and flow cytometry, we demonstrate that, in photosensitized cells, mitochondria undergo structural and functional alterations which can lead cells to apoptosis. Interestingly, in our system some cells were able to survive 72 h post-treatment and to recover, exhibiting the same mitochondrial structure, distribution and inner membrane potential as those in untreated controls. Taking into account that the photoactive molecules redistribute dynamically inside the cell upon RB-Ac administration, it may be hypothesized that cells can be differently affected by irradiation, depending on the relative amount and organelle location of the photosensitizer.

Melatonin reduces early changes in intramitochondrial cardiolipin during apoptosis in U937 cell line

Cardiolipin (CL) is found exclusively in the inner mitochondrial membrane. CL deficiency leads to an alteration in the stability of mitochondrial membranes, to an increased permeability as well as a decreased respiratory rate, and therefore to mitochondria which are completely dysfunctional. It is known that reactive oxygen species (ROS) cause a decrease and a variation in CL content, concomitantly the formation of the mitochondrial permeability transition pore facilitates the release of cytochrome c (cyt c) into the cytosol. Melatonin (Mel), the secretory product of the pineal gland, is a potent and efficient endogenous radical scavenger. It has been shown to protect, various biomolecules, such as DNA, membrane lipids, and cytosolic proteins from oxidative damage. To evaluate the protective role of Mel, we have studied U937 cells treated with UV-B irradiation. In our model, the administration of 1mM Mel before UV-B irradiation showed a significant protection from apoptotic cell death, in particular, mitochondrial structure and function were preserved through apoptotic pathways when cells were preincubated with 1mM Mel before UV-B exposure. The cardiolipin-sensitive probe 10-nonyl acridine orange (NAO) was used to monitor changes in mitochondrial lipids. Our data suggest that the Mel treatment protects CL from ROS and this suggests a possible link with the reduction of the apoptotic phenomenon.