Seasonal plasticity in immunocompetent cytokines (IL-2, IL-6, and TNF-α), myeloid progenitor cell (CFU-GM) proliferation, and LPS-induced oxido-inflammatory aberrations in a tropical rodent Funambulus pennanti: role of melatonin

In seasonal breeders, photoperiods regulate the levels of circulatory melatonin, a well-known immunomodulator and an antioxidant. Melatonin is known to play a complex physiological role in maintaining the immune homeostasis by affecting cytokine production in immunocompetent cells. In this study, we have quantified seasonal and temporal variations in immunocompetent cytokines-IL-2, IL-6, and TNF-α-and circulatory corticosterone along with in- vitro proliferation of bone marrow-derived granulocyte macrophage-colony forming unit (CFU-GM) progenitor cells of a tropical seasonal breeder Funambulus pennanti (northern palm squirrel). Transient variations in antioxidant status of seasonal breeders might be due to the fluctuations associated with immunity and inflammation. Further, to establish a direct immunomodulatory effect of photoperiod, we recorded the LPS-induced oxidative and inflammatory responses of squirrels by housing them in artificial photoperiodic chambers mimicking summer and winter seasons respectively. We observed a marked variation in cytokines level, melatonin, and corticosterone , and CFU-GM cell proliferation during summer and winter seasons. High Peripheral melatonin levels directly correlated with cytokine IL-2 levels, and inversely correlated with TNF-α, and circulatory corticosterone level. LPS-challenged squirrels housed in short photoperiod (10L:14D; equivalent to winter days) showed a marked reduction in the components of the inflammatory cascade, CRP, TNF-α, IL-6, NOx, NF-κB, Cox-2, and PGES, with an overall improvement in antioxidant status when compared to squirrels maintained under a long photoperiod (16L:8D; equivalent to summer days). Our results underline the impact of seasonality, photoperiod, and melatonin in maintaining an intrinsic redox-immune homeostasis which helps the animal to withstand environmental stresses.

Shift and longtime light induces endometrioid adenocarcinoma via activation of PKC-α/Akt pathway in female golden hamster: Involvement of altered Aanat and Bmal1 rhythm

Female night-workers get exposed to frequent light shifts, hence have altered circadian rhythm and are at high risk of endometrial cancer; the underlying mechanism however is still not clear. We, therefore examined the effect of long light exposure (16L:8D, LD1) and regular shift (8 hours) in long nighttime (LD2) on endometrial changes of female golden hamsters. Morphometric analysis, SEM imaging, Alcian blue staining and cytological nuclear atypia of endometrial stromal cells (ESCs) confirmed the incidence of endometrial adenocarcinoma in LD2 exposed hamsters. But, less severe pathomorphological alterations were noted in uterus of LD1 exposed hamsters. Altered Aanat and Bmal1 mRNA, melatonin rhythm, downregulation of important marker gene of adenocarcinoma like Akt, 14-3-3, and PR protein expression and upregulation PKCα, pAkt-S473 and VEGF were observed in LD2 exposed hamsters suggesting the endometrial adenocarcinoma. Further, our western blot analysis supported the immunohistochemical localization of PR, PKCα, and VEGF in uterine tissues along low progesterone. Overall, our data indicates that light shift and long light exposure potentially induced endometrioid adenocarcinoma via activation of PKC-α/Akt pathway in female hamsters. Therefore, duration of light is essential for female normal uterine function. This article is protected by copyright. All rights reserved.

BPS-induced ovarian dysfunction: Protective actions of melatonin via modulation of SIRT-1/Nrf2/NFĸB and IR/PI3K/pAkt/GLUT-4 expressions in adult golden hamster

Ever-increasing occurrence of plastic-manufacturing industries leads to environmental pollution that has been associated with declined human health and increased incidence of compromised reproductive health. Female subfertility/infertility is a complex phenomenon and environmental toxicants as well as lifestyle factors have a crucial role to play. Bisphenol S (BPS) was believed to be a "safer" replacement of bisphenol A (BPA) but recent data documented its neurotoxic, hepatotoxic, nephrotoxic, and reprotoxic attributes. Hence based on the scarcity of reports, we investigated molecular insights into BPS-induced ovarian dysfunction and protective actions of melatonin against it in adult golden hamsters, Mesocricetus auratus. Hamsters were administered with melatonin (3 mg/kg BW i.p. alternate days) and BPS (150 mg/kg BW orally every day) for 28 days. BPS treatment disrupted hypothalamo-pituitary-ovarian (HPO) axis as evident by reduced gonadotropins such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH), ovarian steroids such as estradiol (E2) and progesterone (P4), thyroid hormones namely triiodothyronine (T3) and thyroxine (T4) and melatonin levels along with their respective receptors (ERα, TRα, and MT-1) thereby reducing ovarian folliculogenesis. BPS exposure also led to ovarian oxidative stress/inflammation by increasing reactive oxygen species and metabolic disturbances. However, melatonin supplementation to BPS restored ovarian folliculogenesis/steroidogenesis as indicated by increased number of growing follicles/corpora lutea and E2/P4 levels. Further, melatonin also stimulated key redox/survival markers such as silent information regulator of transcript-1 (SIRT-1), forkhead box O-1 (FOXO-1), nuclear factor E2-related factor-2 (Nrf2), and phosphoinositide 3-kinase/protein kinase B (PI3K/pAkt) expressions along with enhanced ovarian antioxidant capacity. Moreover, melatonin treatment reduced inflammatory load including ovarian nuclear factor kappa-B (NFĸB), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) expressions, serum tumor necrosis factor α (TNFα), C-reactive protein (CRP) and nitrite-nitrate levels as well as upregulated ovarian insulin receptor (IR), glucose uptake transporter-4 (GLUT-4), connexin-43, and proliferating cell nuclear antigen (PCNA) expressions in ovary thereby ameliorating inflammatory and metabolic alterations due to BPS. In conclusion, we found severe deleterious impact of BPS on ovary while melatonin treatment protected ovarian physiology from these detrimental changes suggesting it to be a potential preemptive candidate against environmental toxicant-compromised female reproductive health.

Impact of photoperiod on uterine redox/inflammatory and metabolic status of golden hamster, Mesocricetus auratus

Photoperiod modulates reproductive physiology at multiple levels in seasonally breeding animals. Golden hamsters are long-day breeders that diminish their fertility during the short days. Photoperiod is known to regulate hormonal milieu and uterus is a hormone-sensitive dynamic tissue. However, there is lack of molecular insight regarding the impact of photoperiod on uterine physiology with respect to redox and metabolic status in Mesocricetus auratus. We evaluated the impact of photoperiod on circulatory hormonal parameters (triiodothyronine [T3], thyroxin [T4], estradiol [E2], progesterone [P4], melatonin, and insulin), their receptor expressions and key markers associated with redox (SIRT-1/FOXO-1), inflammatory (NFĸB/COX-2) and metabolic (IR/GLUT4) status in uterus. Adult female golden hamsters were exposed to different photoperiodic regimes, that is, short photoperiod (SP; 8L:16D) and long photoperiod (LP; 16L:8D) for 12 weeks. SP drastically decreased peripheral hormone profiles (T3, T4, E2, and P4) and compromised uterine histoarchitecture when compared with LP-exposed hamsters. Further, SP markedly decreased thyroid hormone receptor-α (TRα), insulin receptor, and glucose uptake transporter-4 (GLUT-4) expressions in uterus. We noted enhanced uterine oxidative (increased MDA and decreased SOD/CAT levels), SIRT-1/FOXO-1 expression and inflammatory (NFĸB/COX-2) load in SP condition. Further, elevated levels of circulatory insulin, melatonin, and its receptor (MT-1) expression in uterus was noted under SP condition. Thus, we may suggest that photoperiod might regulate uterine seasonality through modulation of local hormonal and redox/metabolic homeostasis thereby may restrict offspring bearing capacity under short days.

Circadian desynchronization in pregnancy of Golden hamster following long time light exposure: Involvement of Akt/FoxO1 pathway

Coordination between central and peripheral reproductive clocks in females is poorly understood. Long light is having a hazardous effect on reproductive health. Hence, explored the effect of long-time light exposure (LLD; 16L:8D) on the central and peripheral reproductive (ovary and uterus) clock genes (Bmal1, Clock, Per1, Per2, Cry1 and Cry2) and its downstream regulators (Aanat, Egf, Cx26, Cx43, ERα, pAktS-473, pAktT-308, pFoxO1T-24, 14-3-3, HoxA10, HoxA11 and Pibf) expression in non-pregnant and pregnant Golden hamster. Young adult Golden hamsters were exposed to LLD for 30 days and then were mated. We observed that LLD exposure increased the thickness of the endometrium and reduced myometrium thickness, resembling uterine adenomyosis. In non-pregnant females LLD altered the expressions of clock genes in suprachiasmatic nuclei (SCN), ovary and the uterus along with serum estradiol rhythm. LLD upregulated Egf and downregulated Aanat, Cx26, and Cx43 mRNA levels in uterus. LLD upregulated Akt/FoxO1 phosphorylation and 14-3-3 expressions in the uterus of nonpregnant females. LLD exposure to pregnant females lowered serum progesterone, Aanat, Pibf, Hoxa10, and Hoxa11 mRNA expressions on D4 (peri-implantation) and D8 (post-implantation) resulting in a low implantation rate on D8 (post-implantation). Hence it is evident that the frequent pregnancy anomalies noted under a long light schedule might be due to desynchronization in Aanat, Pibf, Hoxa10, and Hoxa11 as well as the central and peripheral clock genes (Bmal1, Clock, Per1, Per2, Cry1 and Cry2). LLD exposure desynchronized the central and peripheral reproductive clock affecting uterine physiology via Akt/FoxO1 pathway in Golden hamsters. Thus, LLD is a risk factor for female reproductive health and fertility.

Melatonin attenuates LPS-induced ovarian toxicity via modulation of SIRT-1, PI3K/pAkt, pErk1/2 and NFĸB/COX-2 expressions

The association between inflammation and metabolic disturbances leads to various female pathophysiological conditions. Bacterial lipopolysaccharide (LPS), found in the outer membrane of gram-negative bacteria, elicits an oxidative and inflammatory response that profoundly interferes with female reproductive health. We investigated the ameliorative action of melatonin on LPS-induced ovarian pathophysiology in golden hamsters, Mesocricetus auratus. Hamsters were administered with exogenous melatonin (5 mg/kg BW) and LPS (100 μg/kg BW) intraperitoneally for 7 days. LPS treatment impaired ovarian folliculogenesis as evident by histoarchitecture (elevated number of atretic follicles, reduced number of growing follicles and corpus luteum) and steroidogenesis (decreased aromatase/ERα, estradiol and progesterone). On the other hand, LPS administration also perturbed thyroid hormone (T3 and T4) homeostasis, ovarian melatonin receptor (MT-1) expression, antioxidant potential (SOD and catalase) and concomitantly elevated nitro-oxidative stress (decreased SOD, catalase and elevated CRP, TNFα and nitrate/nitrite level) and inflammatory load (NFĸB and COX-2) which culminated into ovarian follicular apoptosis (elevated caspase-3). LPS also disrupted metabolic homeostasis as indicated by hyperinsulinemia with a simultaneous decrease in ovarian IR/GLUT-4 and glucose content. Moreover, LPS treatment decreased expressions of key markers of ovarian physiology (SIRT-1, pErk1/2, PI3K and pAkt). Melatonin co-treatment with LPS improve these detrimental changes proposing melatonin as a potent therapeutic candidate against ovarian dysfunction induced by endotoxin.

Lactate-Dependent Cross-Talk Between Astrocyte and GnRH-I Neurons in Hypothalamus of Aged Brain: Decreased GnRH-I Transcription

GnRH-I produced by hypothalamic neurosecretory cells is considered a master regulator of mammalian reproduction. Although GnRH-I transcription is well studied, the effect of ageing on transcriptional regulation of GnRH-I has not yet been explored. Here, we elucidate the effects of ageing on the metabolic environment like lactate level and TNF-α and how these affect GnRH-I transcription. Using pathway analysis of transcriptomic data, we found that lactate is upregulated in ageing astrocytes due to the downregulation of cellular respiration pathways possibly resulting in greater pyruvate concentration for lactate production. This lactate could then be shuttled into neurons where it would affect GnRH-I transcription. We showed that supra-physiological level of lactate in young mouse brain can mimic metabolic disturbances in the old brain and cause downregulation in GnRH-I transcription at a young age. In particular, we found upregulation of GnRH-I repressors in the young brain treated with high levels of lactate similar to old brain. Hence, this confirmed that aged metabolic environment can affect GnRH-I transcription even in the young brain. Further downstream analysis using the TRUST database showed NF-Kb signalling which lies downstream of both lactate and TNF-α as being capable of upregulating GnRH-I repressors. Since NF-Kb signalling has been shown in our study as well as others to be induced by TNF-α during ageing, it is likely that GnRH-I transcriptional regulation is mediated through these pathways. Thus, we formed a model for explaining the downregulation of GnRH-I transcription during ageing through differential expression of its TFs in an aged metabolic environment.

Stress associated ovarian dysfunctions in a seasonal breeder Funambulus pennanti: Role of glucocorticoids and possible amelioration by melatonin

Studies have shown that stress caused by lack of physical activity disrupts the normal pattern of glucocorticoid secretion which adversely affects the reproductive axis. We studied the effect of chronic movement restriction on ovarian responses in the Indian Palm Squirrel Funambulus pennanti, a highly active diurnal rodent. Physical restraint of squirrels induced stress that led to a significant increase in plasma cortisol, corticosterone and decreased 17β-estradiol level leading to follicular atresia. Ovarian Reactive Oxygen Species (ROS) content, lipid peroxidation (LPO), activities of superoxide dismutase (SOD) and catalase (CAT) enzymes increased in restrained squirrels. Elevated ROS increased the oxidative load that led to ovarian cell death as evidenced by increased Bax and decreased Bcl2 expression causing further decline in Aromatase and ERα proteins. To elaborate the mechanism(s) involved in stress induced glucocorticoid mediated oxidative damages to the ovary we extended our study by exposing ovaries in vitro to the synthetic glucocorticoid dexamethasone (200 μM). We observed that glucocorticoid receptor (GR) expression was significantly increased in dexamethasone treated ovaries in vitro with a decrease in expression of Nrf2 and HO-1 proteins. Melatonin supplementation (10 nM) along with dexamethasone significantly decreased ovarian ROS production, lipid peroxidation and increased antioxidant enzyme activities by improving the expression of Nrf2 and HO-1, reinstating the cellular redox homeostasis. Therefore, it can be suggested that physical restraint induced glucocorticoid and its receptor activation interfered with the ovarian antioxidant defense mechanism. Melatonin via its receptor MT1 significantly alleviated ovarian damages acting as a cytoprotective agent.

Photoperiodic modulation of ovarian metabolic, survival, proliferation and gap junction markers in adult golden hamster, Mesocricetus auratus

Female reproductive physiology is greatly dependent on tight regulation of metabolic and survival factors. Photoperiod regulates female reproductive rhythms but very less information exists explaining whether photoperiod could modulate thyroid hormone homeostasis, metabolic/energy parameters along with survival, proliferation and gap junction proteins in the ovary of a long-day breeder, Mesocricetus auratus. Adult female hamsters were exposed to different photoperiodic regimes i.e., critical photoperiod (CP; 12.5L:11.5D), short photoperiod (SP; 8L:16D) and long photoperiod (LP; 16L:8D) for 12 weeks. LP upregulated thyroidal and gonadal activity as apparent by histoarchitecture, thyroid hormone profile [triiodothyronine (T3), thyroxin (T4) and thyroid stimulating hormone (TSH)], luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol (E2) and progesterone (P4) levels when compared with SP exposed hamsters. Further, LP increased thyroid hormone receptor-α/deiodinase-2 (TRα/Dio-2), estrogen receptor-α (ERα)/aromatase and insulin receptor/glucose transporter-4 (IR/GLUT-4) expressions in ovary. Interestingly, ovarian sirtuin-1 (SIRT-1) expression was also upregulated under LP condition along with cell proliferation (proliferating cell nuclear antigen or PCNA), survival (B cell lymphoma-2 or Bcl-2) and gap junction (connexin-43) markers when compared to SP exposed hamsters. We also noted elevated levels of circulatory leptin, insulin along with melatonin and its receptor (MT-1) in ovary under SP condition. Thus, we suggest that photoperiod plays a vital role in regulation of thyroid and reproductive hormone homeostasis along with key metabolic and survival markers in the ovary of adult golden hamsters, M. auratus providing further insight into the regulation of female reproductive seasonality in a long-day breeder.

Uterine anomalies in cell proliferation, energy homeostasis and oxidative stress in PCOS hamsters, M. auratus: Therapeutic potentials of melatonin

AIMS

Polycystic ovarian syndrome (PCOS) is a reproductive, endocrine and metabolic disorder. Less is known about the mechanism of its effect on uterine function and therapeutic potential of melatonin. Our aim was to evaluate uterine dysfunction(s) in letrozole induced PCOS and its possible rectification by melatonin.

MAIN METHODS

Adult female golden hamsters were divided into groups of Control (C), Melatonin (M; 1 mg/kg b.w.), Letrozole (L; 3 mg/kg b.w.) and combination of Letrozole+Melatonin (L + M; 3 mg/kg b.w. + 1 mg/kg b.w.) which were treated for 40 days. Analysis of serum testosterone/estradiol/progesterone/leptin/insulin, uterine histomorphometry, immunohistochemistry for proliferation cell nuclear antigen (PCNA), homeostatic assessment model of insulin resistance (HOMA-IR), western blotting for PCNA, androgen receptor (AR), insulin receptor (InsR), glucose tansporter-4 (GLUT-4), nuclear factor-kappa B (NFκB), cyclooxygenase-2 (COX-2) and biochemical analysis of superoxide dismutase (SOD)/catalase/lipid peroxidation (LPO) were done.

KEY FINDINGS

Serum testosterone, leptin and insulin increased while uterine InsR/GLUT-4 expression decreased in L group indicating metabolic abnormalities. Endometrial hyperplasia, increased expression of PCNA and AR indicated abnormal proliferation in L compared to C. Increased uterine oxidative load (SOD/catalase/LPO) and inflammatory markers NFκB/COX-2 expression in L was responsible for high tissue oxidative stress and inflammation. M administration normalized all the above parameters suggesting its ameliorative effect in L + M group.

SIGNIFICANCE

We report PCOS induced uterine dysfunction in Mesocricetus auratus for the first time. M administration restores uterine functions modulating cellular dynamicity, metabolic status, decreased oxidative and inflammatory load in PCOS hamsters. Therefore, we suggest the therapeutic potential of M against PCOS led uterine abnormalities to restore female fertility.

Role of melatonin and HSF-1\HSP-70 in modulating cold stress-induced immunosuppression in a tropical rodent- Funambulus pennanti [Volume 87, January 2020, 102456]

The neuroendocrine hormone melatonin and molecular chaperones (heat shock proteins) are evolutionarily conserved molecules that play an important role in protecting organisms from abiotic and biotic stressors. Environmental temperature and seasonality modulates immunity which impacts the overall health of animals. Most studies in relation to thermal stress are based on animals inhabiting temperate zones however, the substantial effect of climatic stress on tropical animals is less explored. Therefore, in this study we focused on the immunosuppressive effect of cold environment on a seasonally breeding tropical rodent and highlighted the importance of melatonin and HSF-1/Hsp-70 in regulating immunity. Animals were exposed to different temperatures with or without melatonin treatment. Our results suggest that, low temperature elicited cold-associated stress in animals marked by reduced body weight, decreased TLC/LC count in the blood and increased corticosterone production which was central to all immune alterations. Cold temperature also increased the oxidative stress which further induced apoptosis in the immune cells and activated stress response molecular chaperones HSF-1/HSP-70. Exogenous melatonin treatment not only ameliorated cold-induced immune suppression but also upregulated the expression of HSF-1 and HSP-70 in the immune cells thereby preventing protein unfolding and cell death. Thus, we conclude that melatonin and molecular chaperones synergistically alleviated immune suppression and could emerge as a promising combination therapy to target temperature stress in animals while boosting immunity.

Melatonin ameliorates Bisphenol S induced testicular damages by modulating Nrf-2/HO-1 and SIRT-1/FOXO-1 expressions

BPS has detrimental effects on human reproductive health and emerged as an environmental contaminant for global health concern. This study deals with the adverse impact of BPS exposure on testicular oxidative stress, inflammation and apoptosis in adult male golden hamster, Mesocricetus auratus and its amelioration by melatonin. BPS (75 mg/kg BW/day) exposure caused testicular impairment as evident by histological degenerative changes, declined sperm quality (viability and motility), serum levels of testosterone and melatonin with a concomitant decrease in testicular androgen receptor (AR) and melatonin receptor (MT1) expression. The BPS exposure caused marked increase in testicular oxidative load, inflammation (NF-kB/COX-2) and apoptosis (caspase-3). Melatonin (10 mg/kg BW/alternate day) pretreatment to BPS exposed hamsters resumed normal testicular histoarchitecture, sperm quality and decreased testicular oxidative load as evident by enhanced antioxidant enzymes (SOD and catalase) activities and decreased lipid peroxidation (LPO) level. Further, melatonin also stimulated the testicular antioxidant proteins Nrf-2/HO-1, SIRT-1/FOXO-1 and reduced inflammatory proteins NF-kB/COX-2 expression to counteract BPS induced testicular damages. Melatonin administration to the BPS treated hamsters resulted in increased testicular cell proliferation (PCNA), survival (Bcl-2), gap junction (connexin-43) and decreased apoptosis (caspase-3). In conclusion, our study documented the detrimental effects of BPS on testes that compromises male fertility. Further, melatonin was found as a potent molecule that rescued the BPS induced testicular damages in male golden hamster Mesocricetus auratus.

Retinal and extra-retinal photoreceptor responses and reproductive performance of Japanese quail (Coturnix coturnix japonica) following exposure to different photoperiodic regime

Japanese quail is a truly photoperiodic avian species. In general long days are gonado-stimulatory and short days are gonado-inhibitory for this poultry bird. To investigate the correlation of retinal and extra-retinal photoreceptors with different photoperiodic conditions quail were divided into 2 groups and kept under long day (16L: 8D) and short day (8L: 16D) condition separately to develop photosensitivity and scotosensitivity respectively. Transfer of long day quail to intermediate day-length (13.5L: 10.5D) developed photorefractoriness (relative) and prolonged exposure to short photoperiodic conditions led the birds to develop scotorefractoriness. Increased expression of mRNA and immunosignaling of photoreceptors rhodopsin, transducin in eye and hypothalamus while decreased mRNA expression of melatonin receptors (Mel1b, Mel1c) were noted in the eyes of photosensitive (PS) and scotorefractory (SR) quail compared to photorefractory (PR) and scotosensitive (SS) birds respectively. Decreased expression of hypothalamic GnIH and melatonin receptors mRNA was observed in PS and SR birds compared to PR and SS birds respectively. Modulation of retinal and extra retinal photoreceptors leads to increased spermatogenesis as well as mRNA expression of steroidogenic genes and androgen receptor in the testis of sexually active PS and SR quail. These results led us to conclude that gonadal stimulation in PS as well as SR quail is outcome of activated retinal and extra retinal photoreceptors which lowered melatonin receptors and GnIH expression. Contrarily testicular inhibition in PR and SS is the outcome of decreased photoperception. It is suggested that decreased photoperception in SS quail increases after prolong exposure of the short day (in SR) leading to increased activity of HPG axis.

Fluoride Compromises Testicular Redox Sensor, Gap Junction Protein, and Metabolic Status: Amelioration by Melatonin

The excess fluoride intake has been shown to adversely affect male reproductive health. The aim of the present study was to investigate the key mechanism underlying fluoride-induced testicular dysfunction and the role of melatonin as a modulator of testicular metabolic, oxidative, and inflammatory load. The present results indicated that sodium fluoride (NaF) exposure to adult male golden hamsters severely impairs reproductive physiology as evident from markedly reduced sperm count/viability, testosterone level, androgen receptor (AR), testicular glucose transporter (GLUT-1), gap junction (connexin-43), and survival (Bcl-2) protein expression. NaF exposure markedly increased testicular oxidative load, inflammatory (NF-kB/COX-2), and apoptotic (caspase-3) protein expression. However, melatonin treatment remarkably restored testicular function as evident by normal histoarchitecture, increased sperm count/viability, enhanced antioxidant enzyme activities (SOD and Catalase), and decreased lipid peroxidation (LPO) level. In addition, melatonin treatment upregulated testicular Nrf-2/HO-I, SIRT-1/ FOXO-1, and downregulated NF-kB/COX-2 expression. Further, melatonin ameliorated NaF-induced testicular metabolic stress by modulating testicular GLUT-1expression, glucose level, and LDH activity. Furthermore, melatonin treatment enhanced testicular PCNA, Bcl-2, connexin-43, and reduced caspase-3 expression. In conclusion, we propose the molecular mechanism of fluoride-induced testicular damages and ameliorative action(s) of melatonin.

Trade-off expression of melatonin receptor subtypes (Mel1a and Mel1b) and androgen receptor in lung of a tropical bird, Perdicula asiatica

The role of circulatory steroid hormone along with melatonin in lung of any seasonally breeding bird has never been explored so far. This could be interesting because steroid hormones are immunosuppressive while melatonin is immunostimulatory in nature. In our present study, we report the effect of exogenous melatonin and testosterone on expression of melatonin receptor subtypes (Mel_1a and Mel_1b ) and androgen receptor in lung of a tropical bird Perdicula asiatica. Birds were collected from vicinity of Varanasi and acclimatized in laboratory with sufficient food and water. The birds were treated with melatonin and testosterone at dose of 25 µg/100 g B.wt./day and 1 mg/100 g B.wt./day, respectively, for 28 days. At the end of the experiment, the birds were sacrificed and lung tissue and blood sample were collected for immunohistochemistry, Western blot analysis and hormonal assay. Testosterone treatment increased circulatory testosterone and upregulated expression of androgen receptors whereas downregulated expression of melatonin receptor subtypes Mel_1a and Mel_1b . Melatonin administration increased peripheral melatonin and upregulated expression of melatonin receptor subtypes Mel_1a and Mel_1b while downregulated androgen receptor. Thus, our results suggest that a trade-off relationship between melatonin and testosterone exists in regulation of their receptors in lung of Perdicula asiatica.

Paraquat induced impaired reproductive function and modulation of retinal and extra-retinal photoreceptors in Japanese quail (Coturnix coturnix japonica)

Paraquat (PQ) being a potent herbicide, causes toxic effect on growth, development and reproduction of plant as well as in animals. In this study we have mainly focused on the toxic effect of PQ on photoperception via different photoreceptors present in retina, pineal and hypothalamus and thereby its effect on hypothalamic - pituitary - gonadal (HPG) axis. PQ was administered i.p.10 mg/kg body weight daily for 1 week in poultry birds Japanese quail (Coturnix coturnix japonica). Our findings clearly indicated decrease in immunoreactivity of retinal and extra retinal photoreceptors (Iodopsin, rhodopsin and transducin) following PQ treatment in comparison to control group. Increased immunoreactivity of GnIH was observed in testis and epididymis of PQ treated group. Decreased mRNA expression of photoreceptors (rhodopsin and melanopsin), steroidogenic genes, androgen receptor, GnRH-I were found in PQ treated group while increased mRNA expression of melatonin receptors (Mel 1a R, Mel 1b R, Mel 1c R) and GnIH were found in PQ treated group. Thus, from the present results it may be concluded that PQ treatment alters the photoperception via altering the expression of photoreceptors and also modulates the HPG axis thereby alters the reproductive functions in Japanese quails.

Comparative effect of melatonin and quercetin in counteracting LPS induced oxidative stress in bone marrow mononuclear cells and spleen of Funambulus pennanti

A majority of cellular diseases, independent of their origin, are characterized by a dramatic increase in Reactive Oxygen Species (ROS) in response to stress. In most cases, the uncontrolled detrimental ROS outburst is difficult to handle for the cellular machinery and eventually leads to cell mortality. In this study, we compare the antioxidant efficacy of quercetin and melatonin to find out a better alternative against lipopolysaccharide (LPS) induced tissue injury by oxidative stress in Funambulus pennanti. Transient exposure to LPS significantly increased ROS generation and lipid peroxidation levels in bone marrow mononuclear cells (MNCs) and spleen which was further corroborated by decreased activities of SOD, CAT and Gpx enzymes. It also downregulate the expression of cellular oxidative stress response proteins Nrf-2 and HO-1 in spleen and decreases the proliferation of bone marrow derived Granulocyte macrophage-colony forming unit cells (GM-CFU). Both melatonin and quercetin pre-treatments rescued these effects, however, our results indicated that the efficacy of melatonin to overcome oxidative stress was significantly better than quercetin. Our findings support the idea that melatonin is a better antioxidant and immunomodulator as compared to other alternatives and perhaps may be employed in the development of effective therapeutics against ROS dominated diseases.

Short day length enhances physiological resilience of the immune system against 2-deoxy-d-glucose-induced metabolic stress in a tropical seasonal breeder Funambulus pennanti

Studies demonstrate the importance of metabolic resources in the regulation of reproduction and immune functions in seasonal breeders. In this regard, the restricted energy availability can be considered as an environmental variable that may act as a seasonal stressor and can lead to compromised immune functions. The present study explored the effect of photoperiodic variation in the regulation of immune function under metabolic stress condition. The T-cell-dependent immune response in a tropical seasonal breeder Funambulus pennanti was studied following the inhibition of cellular glucose utilization with 2-deoxy-d-glucose (2-DG). 2-DG treatment resulted in the suppression of general (e.g., proliferative response of lymphocytes) and antigen-specific [anti-keyhole limpet hemocyanin IgG titer and delayed-type hypersensitivity response] T-cell responses with an activation of the hypothalamic-pituitary-adrenal axis, which was evident from the increased levels of plasma corticosterone. 2-DG administration increased the production of inflammatory cytokines [interleukin (IL)-1β and tumor necrosis factor (TNF)-α] and decreased the autocrine T-cell growth factor IL-2. The immunocompromising effect of 2-DG administration was retarded in animals exposed to short photoperiods compared with the control and long photoperiod-exposed groups. This finding suggested that short photoperiodic conditions enhanced the resilience of the immune system, possibly by diverting metabolic resources from the reproductive organs toward the immune system. In addition, melatonin may have facilitated the energy "trade-off" between reproductive and immune mechanisms, thereby providing an advantage to the seasonal breeders for their survival during stressful environmental conditions.

Supplementation of corn seed with regular diet modulates immune function and antioxidant status in Capra hircus

Melatonin modulates the functional activation of antioxidative enzymes to maintain the oxidant-antioxidant balance in the physiological system. Melatonin administration via subcutaneous injection increases endogenous melatonin concentration that has been used to modulate the immune function in rodents and reproductive activity in small ruminant like goats. However, to date, no report exist which could suggest the effect of corn seed supplementation on the endogenous melatonin concentration and its impact on cellular-immune function and antioxidative enzymes activity in any small ruminant like goats. Therefore, in this study, Zea mays (corn seeds), as source of melatonin, were supplemented with regular diet to explore its impact on endogenous melatonin concentration in goat, Capra hircus. Zea mays supplementation with regular diet for 40 days significantly elevated the endogenous melatonin concentration, proliferative response of peripheral blood mononuclear cells and antioxidative enzymes activity along with total antioxidant capacity of the plasma. An increase in circulatory IL-2 and IL-6 level along with declined TNF-α, malondialdehyde and nitric oxide was noted with elevated endogenous melatonin concentration. In conclusion, it might be suggested that corn seed could be used as supplement to modulate endogenous melatonin concentration that may improve cellular-immune function and antioxidant status. The corn seed might also be included as nutraceutical in regular diet to maintain immune-antioxidant homoeostasis in other species.

Effect of Naltrexone on photoperiodic regulation of testicular steroidogenesis in adult golden hamster, Mesocricetus auratus

Photoperiodic regulation of testicular steroidogenesis through modulation of MT1R expression and local melatonin content is well established. However, additional mediators besides local melatonergic system in photoperiodic control of testicular steroidogenesis in golden hamster have not been studied in detail. Endogenous opioid peptides (EOP) are known to regulate reproduction via acting at multiple levels of the hypothalamus-pituitary-gonadal (HPG) axis. The presence of β-endorphin, a naturally occurring opioid peptide, and its receptor (μ-opioid receptor, μOR) has been reported in rat testes; however the functional significance of photoperiodic regulation μOR in testicular steroidogenesis is not clear. In the present study, we assessed the effect of Naltrexone (Nal), a μOR antagonist, in photoperiodic regulation of testicular steroidogenesis. Immunohistochemical (IHC) localization and expression of μOR along with the expression of steroidogenic markers in testes was analyzed through western blot analyses. IHC suggest immunoreactivity for μOR in Leydig cells with strong immunoreactivity under SD (short-day) condition, whereas weak immunoreactivity was observed under LD (long-day). The expression of μOR was significantly decreased following Nal administration in both the photoperiodic conditions. The localization and differential photoperiodic regulation of μOR in Leydig cells suggests its involvement in testicular steroidogenesis. Further, Nal administration significantly increased the expression of steroidogenic markers (AR, StAR, P450_SCC, LH-R, 3β-HSD and 17-HSD) and plasma testosterone concentration under SD condition as compared to SD-control. We may therefore suggest that photoperiod differentially regulates the expression of μOR which thereby mediates the inhibitory effect of melatonin on testicular steroidogenesis.

Photoperiodic modulation of local melatonin synthesis and its role in regulation of thymic homeostasis in Funambulus pennanti

The effect of photo-neuroendocrine system on the thymic (immune) functions is mediated by gonadal steroid and the pineal hormone melatonin. The present study explored the effect of photoperiod on the thymic melatonergic system and its role in protection of thymic T-cells from the testosterone induced seasonal oxidative stress and apoptosis. Exposure to long day-length (LD) was noted to decrease local (thymic) melatonin content and induce oxidative stress and apoptosis in the thymus. Increased peripheral level of testosterone upregulated the androgen receptor expression and, consequently reduced proliferation response of the thymocytes. Short day conditions (SD) however, reversed the effect of LD on the thymic physiology. Low level of testosterone was concomitant with diminished nitro-oxidative stress and decreased expression of redox sensitive factors (NF-κB, p53 and Bax/Bcl-2 ratio) in the thymus. SD retarded activation of caspase-3 resulting in procaspase-3 accumulation. Further, in vitro treatment of thymocytes with AR antagonist flutamide impaired the sensitivity of thymocytes to androgen and reversed the deleterious effects of testosterone on the proliferative and apoptotic responses of thymocytes. Therefore, it can be suggested that thymus derived melatonin protects thymic T-cells from testosterone induced seasonal oxidative stress, apoptosis and also acts as a potent paracrine factor for maintenance of redox status to ensure thymocyte survival.

Melatonin modulates glucocorticoid receptor mediated inhibition of antioxidant response and apoptosis in peripheral blood mononuclear cells

Pineal melatonin is known for its immunomodulatory and anti-stress properties. It modulates stress condition by regulating antioxidant responses and apoptosis in the immune cells. Stress causes increased glucocorticoid level that acts through glucocorticoid receptor (GR) and is translocated into nucleus under regulation of HSP90 based chaperone machinery. Melatonin influences glucocorticoid and GR mediated stress condition in rodents, but till date there are no reports which could suggest the effect of melatonin treatment on GR mediated apoptosis and inhibition of Nrf-2/hemeoxygenase-1 (HO-1) induced antioxidant status in immunocompetent cells (peripheral blood mononuclear cells; PBMCs). Therefore, in the present study, we considered GR mediated inhibition of Nrf2 and HO-1 along with anti-apoptotic Bcl-2 expression in PBMCs. The PBMCs were treated with synthetic glucocorticoid; dexamethasone (Dex) and melatonin (Mel), to explore the effect of melatonin treatment in regulation of GR mediated apoptosis and inhibition of antioxidant status in immune cells. It was noted that melatonin treatment retained GR into cytoplasm by inhibiting the dissociation of HSP90 from GR-HSP90 complex and enhanced expression of Nrf2/HO-1 and Bcl-2 expression. This led to increased HO-1 expression and elevated Bcl-2 led to increased Bcl-2/Bax ratio that might ultimately enhanced the cellular antioxidant response and survival under glucocorticoid mediated stress condition. Our observations suggest that the declined GR nuclear translocation upon melatonin treatment might be responsible for the up-regulation of Nrf2 mediated HO-1 activity and increased Bcl-2/Bax ratio in PBMCs to maintain the immune homeostasis under stress condition.

Melatonin alleviates hyperthyroidism induced oxidative stress and neuronal cell death in hippocampus of aged female golden hamster, Mesocricetus auratus

Oxidative stress is a well known phenomenon under hyperthyroid condition that induces various physiological and neural problems with a higher prevalence in females. We, therefore investigated the antioxidant potential of melatonin (Mel) on hyperthyroidism-induced oxidative stress and neuronal cell death in the hippocampus region of brain (cognition and memory centre) of aged female golden hamster, Mesocricetus auratus. Aged female hamsters were randomly divided into four experimental groups (n=7); group-I: control, group-II: Melatonin (5mgkg(-1)day(-1), i.p., for one week), group-III: Hyperthyroid (100μg kg(-1)day(-1), i.p., for two weeks) and group-IV- Hyper+Mel. Hormonal profiles (thyroid and melatonin), activity of antioxidant enzymes (SOD, CAT and GPX), lipid peroxidation level (TBARS) and the specific apoptotic markers (Bax/Bcl-2 ratio and Caspase-3) expression were evaluated. A significant increase in the profile of total thyroid hormone (tT3 and tT4) in hyperthyroidic group as compared to control while tT3 significantly decreased in melatonin treated hyperthyroidic group. However, Mel level significantly decreased in hyperthyroidic group but increased in melatonin treated hyperthyroidic group. Further, the number of immune-positive cells for thyroid hormone receptor-alpha (TR-α) decreased in the hippocampus of hyperthyroidic group and increased in melatonin treated hyperthyroidic group. Profiles of antioxidant enzymes showed a significant decrease in hyperthyroidic group with a simultaneous increase in lipid peroxidation (TBARS). Melatonin treatment to hyperthyroidic group lead to decreased TBARS level with a concomitant increase in antioxidant enzyme activity. Moreover, increased expression of Bax/Bcl-2 ratio and Caspase-3, in hyperthyroidic group had elevated neuronal cell death in hippocampal area and melatonin treatment reduced its expression in hyperthyroidic group. Our findings thus indicate that melatonin reduced the hyperthyroidism-induced oxidative stress and neuronal cell death in the hippocampus region of brain, suggesting a novel therapeutic approach of melatonin for management of cognition and memory function in females under hyperthyroid condition.

Synthesis and in vitro evaluation of melatonin entrapped PLA nanoparticles: an oxidative stress and T-cell response using golden hamster

This study was carried out to evaluate the effects of melatonin entrapped PLA nanoparticles (Mel-NPs) and pure Mel on impact of reactive oxygen species (ROS), blastogenic responses (%SR) in terms of proliferation of splenocytes. ROS have been proposed to play an important role in balancing the pro- and antioxidant homeostasis during different physiological condition of organism. Melatonin has been suggested as an effective free radical scavenger that may have an important role during this process. Mel-NPs were prepared by using emulsification (o/w) nanoprecipitation method and their physicochemical characterizations were studied for evaluation of particle size and encapsulation efficiency by using SEM, TEM, particle size analyzer, DSC and FTIR. The TEM micrograph showed excellent findings regarding size, shape, encapsulation efficiency and difference between pure PLA nanoparticles and Mel-NPs. The SEM micrographs of Mel-NPs showed spherical shape, smooth surfaces and the homogeneous particle size distribution. In TEM micrograph, the average diameter of Mel-NPs was found to be 36 ± 8 nm with ∼78% (w/w) of entrapment efficiency. The size of pure PLA nanoparticles was found to be larger as compared to Mel-NPs which confirm that the drug supports the reduction of the size of Mel-NPs. In in vitro study, we observed that Mel-NPs significantly reduce the level of ROS in splenocytes and increased the level %SR at 96 h of splenocytes culture as compared to the culture with pure Mel. Thus our results propose high clinical value for improvement of depressed immunity by Mel-NPs.

UVB irradiation severely induces systemic tissue injury by augmenting oxidative load in a tropical rodent: efficacy of melatonin as an antioxidant

Tropical animals are regularly exposed to solar UV radiation. The generation and accumulation of free radicals as a result of UVB incidence causes tissue damage. In the present study we report that the irradiation of Funambulus pennanti by 1.5 J/cm(2) of UVB caused significant oxidative damage to the spleen. The systemic immunity suffered collateral damage as depicted by results of total leukocyte count (TLC) while an increase in the thiobarbituric acid reactive substances (TBARS) and decline in the activities of enzymes superoxide dismutase (SOD), Glutathione peroxidase (GSH-Px) and Catalase (CAT) denoted oxidative tissue damage. Melatonin the indole-amine with known antioxidative properties when administered subcutaneously (s.c 100 μg/100 gm body weight), before the UVB irradiation recovered the damages caused by UVB radiation in the spleen. The action of melatonin was direct and might have involved its membrane receptor (MT1) as well as nuclear receptor (RORα) indicating the fact that the mode of action of melatonin in ameliorating UVB radiation induced free radical load may be receptor mediated. Our study hence reports for the first time that UVB radiation incurred oxidative damage to the spleen and suppressed the normal tissue functions. This UVB mitigated oxidative stress was recovered by the free radical scavenging and anti-apoptotic functions of melatonin when administered prior to UVB irradiation.

Melatonin Reverses Fas, E2F-1 and Endoplasmic Reticulum Stress Mediated Apoptosis and Dysregulation of Autophagy Induced by the Herbicide Atrazine in Murine Splenocytes

Exposure to the herbicide Atrazine (ATR) can cause immunotoxicity, apart from other adverse consequences for animal and human health. We aimed at elucidating the apoptotic mechanisms involved in immunotoxicity of ATR and their attenuation by Melatonin (MEL). Young Swiss mice were divided into control, ATR and MEL+ATR groups based on daily (x14) intraperitoneal administration of the vehicle (normal saline), ATR (100 mg/kg body weight) and MEL (20 mg/kg body weight) with ATR. Isolated splenocytes were processed for detection of apoptosis by Annexin V-FITC and TUNEL assays, and endoplasmic reticulum (ER) stress by immunostaining. Key proteins involved in apoptosis, ER stress and autophagy were quantified by immunoblotting. ATR treatment resulted in Fas-mediated activation of caspases 8 and 3 and inactivation of PARP1 which were inhibited significantly by co-treatment with MEL. MEL also attenuated the ATR-induced, p53 independent mitochondrial apoptosis through upregulation of E2F-1 and PUMA and suppression of their downstream target Bax. An excessive ER stress triggered by ATR through overexpression of ATF-6α, spliced XBP-1, CREB-2 and GADD153 signals was reversed by MEL. MEL also reversed the ATR-induced impairment of autophagy which was indicated by a decline in BECN-1, along with significant enhancement in LC3B-II and p62 expressions. Induction of mitochondrial apoptosis, ER stress and autophagy dysregulation provide a new insight into the mechanism of ATR immunotoxicity. The cytoprotective role of MEL, on the other hand, was defined by attenuation of ER stress, Fas-mediated and p53 independent mitochondria-mediated apoptosis as well as autophagy signals.

Therapeutic efficacy and toxicity of tamoxifen loaded PLA nanoparticles for breast cancer

This study was carried out to assess the therapeutic efficacy and toxicity of tamoxifen (Tmx) loaded poly(d,l-lactic acid) (PLA) nanoparticles (Tmx-NPs) for breast cancer. An in vivo study was conducted to determine the effect of Tmx-NPs on DMBA induced mammary tumor in female Wistar rat. The experimental results showed that the mean diameter of Tmx-NPs was 224 ± 3 nm with 68 ± 2% (w/w) of entrapment efficiency. In in vivo study, the tumor size in rat was significantly reduced (P < 0.001) by treating Tmx-NPs as compared to pure Tmx and untreated group (control DMBA). Tmx-NPs showed the marked reduction in hepatotoxicity and renal toxicity when compared to pure Tmx as evidenced by histopathological examination of liver and kidney tissues as well as estimation of AST, ALT levels, and creatinine, urea, blood urea nitrogen levels. Oxidative stress and lipid peroxidation was estimated in spleen, liver and kidney and was found significantly high in pure Tmx treated group as compared to Tmx-NPs and control group. Immunological parameters like blastogenic response of splenocytes, TLC, DLC were studied and found significantly high in pure Tmx treated group but the variations were nonsignificant in Tmx-NPs group as compared to control. Thus, Tmx-NPs have significant therapeutic efficacy with reduced side effects.

Seasonal modulation of immunity by melatonin and gonadal steroids in a short day breeder goat Capra hircus

Role of melatonin in regulation of immunity and reproduction has never been studied in detail in goats. The aim of the present study was to explore hormonal regulation of immunity in goats with special reference to melatonin. Plasma of male and female goats (n = 18 per sex per season) was processed for hormonal (estrogen, testostrone, and melatonin) and cytokine (interleukin [IL-2], IL-6, and tumor necrosis factor α) measurements during three seasons, i.e., summer, monsoon, and winter. To assess cell-mediated immune response, percent stimulation ratio of thymocytes was recorded during three seasons. To support and establish the modulation by hormones, Western blot analysis for expressions of melatonin receptors (MT1, MT2), androgen receptor, and estrogen receptor α and estimations of marker enzymes, arylalkylamine N-acetyltransferase for melatonin and 3β-hydroxysteroid dehydrogenase activities for steroidogenesis were performed in thymus. All the hormones and cytokines were estimated by commercial kits. Biochemical, immunologic, and Western blot analyses were done by standardized protocols. We noted a significant increase in estrogen and testosterone levels (P < 0.05) in circulation during monsoon along with melatonin (P < 0.05) presenting a parallel relationship. Expressions of melatonin receptors (MT1 and MT2) in thymus of both the sexes were significantly high (P < 0.01) during winter. Estrogen receptor α expression in female thymus was significantly high during monsoon (P < 0.05). However, androgen receptor showed almost static expression pattern in male thymus during three seasons. Further, both arylalkylamineN-acetyltransferase and 3β-hydroxysteroid dehydrogenase enzyme activities were significantly high (P < 0.05; P < 0.01, respectively) during monsoon. These results suggest that there may be a functional parallelism between gonadal steroids and melatonin as melatonin is progonadotrophic in goats. Cell-mediated immune parameters (percent stimulation ratio of thymocytes) and circulatory levels of cytokines (IL-2, IL-6, and tumor necrosis factor α) were significantly high (P < 0.01) during monsoon. In vitro supplementation of gonadal steroids to T-cell culture suppressed immunity but cosupplementation with melatonin restored it. Further, we may also suggest that reproductive and immune seasonality are maintained by variations in circulatory hormones and local synthesis of melatonin and gonadal steroids. These functional interactions between melatonin and gonadal steroid might be of great importance in regulating the goat immunity by developing some hormonal microcircuit (gonadal steroid and melatonin) in lymphatic organs.