OBJECTIVES: To study the protective effect of melatonin (Mel) against oxygen-induced retinopathy (OIR) in neonatal mice and the role of the HMGB1/NF-κB/NLRP3 axis. METHODS: Neonatal C57BL/6J mice, aged 7 days, were randomly divided into a control group, a model group (OIR group), and a Mel treatment group (OIR+Mel group), with 9 mice in each group. The hyperoxia induction method was used to establish a model of OIR. Hematoxylin and eosin staining and retinal flat-mount preparation were used to observe retinal structure and neovascularization. Immunofluorescent staining was used to measure the expression of proteins and inflammatory factors associated with the HMGB1/NF-κB/NLRP3 axis and lymphocyte antigen 6G. Colorimetry was used to measure the activity of myeloperoxidase. RESULTS: The OIR group had destruction of retinal structure with a large perfusion-free area and neovascularization, while the OIR+Mel group had improvement in destruction of retinal structure with reductions in neovascularization and perfusion-free area. Compared with the control group, the OIR group had significant increases in the expression of proteins and inflammatory factors associated with the HMGB1/NF-κB/NLRP3 axis, the expression of lymphocyte antigen 6G, and the activity of myeloperoxidase (P<0.05). Compared with the OIR group, the OIR+Mel group had significant reductions in the above indices (P<0.05). Compared with the control group, the OIR group had significant reductions in the expression of melatonin receptors in the retina (P<0.05). Compared with the OIR group, the OIR+Mel group had significant increases in the expression of melatonin receptors (P<0.05). CONCLUSIONS Mel can alleviate OIR-induced retinal damage in neonatal mice by inhibiting the HMGB1/NF-κB/NLRP3 axis and may exert an effect through the melatonin receptor pathway.
Animals ; Mice ; HMGB1 Protein ; Melatonin/therapeutic use* ; Mice, Inbred C57BL ; NF-kappa B ; NLR Family, Pyrin Domain-Containing 3 Protein ; Oxygen/adverse effects* ; Peroxidase ; Receptors, Melatonin ; Retinal Diseases/drug therapy*

Neonatal hypoxic-ischemic encephalopathy (HIE) remains one of the leading causes of death and long-term neurodevelopmental disorders in full-term neonates, and there is currently no curative treatment. Therapeutic hypothermia is now a standard therapy for HIE in the neonatal intensive care unit, but its safety and efficacy in remote areas remains unclear. Melatonin is an indole endocrine hormone mainly produced by the pineal gland and it has the ability to easily penetrate the blood-brain barrier. Through receptor and non-receptor mechanisms, melatonin exerts anti-oxidative and anti-inflammatory effects and participates in the regulation of organelle function and the inhibition of cell death. Melatonin is considered one of the most promising drugs for the treatment of HIE based on its reliable safety profile and clinical/preclinical results. This article reviews the recent research on the use of melatonin in combination with therapeutic hypothermia for the treatment of neonatal HIE.
Infant, Newborn ; Humans ; Melatonin/therapeutic use* ; Hypoxia-Ischemia, Brain/therapy* ; Hypothermia, Induced ; Intensive Care Units, Neonatal

Humans ; Myocardial Reperfusion Injury/prevention & control* ; Melatonin/therapeutic use* ; Mitochondria ; Myocardial Infarction

OBJECTIVE: To investigate the protective effect of melatonin against myocardial ischemia reperfusion (IR) injury in isolated rat hearts and explore the underlying mechanisms. METHODS: The isolated hearts from 40 male SD rats were randomly divided into 4 groups (=10): the control group, where the hearts were perfused with KH solution for 175 min; IR group, where the hearts were subjected to global ischemia for 45 min followed by reperfusion for 120 min; IR+melatonin (Mel+IR) group, where melatonin (5 μmol/L) was administered to the hearts 1 min before ischemia and during the first 5 min of reperfusion, followed by 115 min of reperfusion; and IR+2, 3-butanedione monoxime (IR+BDM) group, where the hearts were treated with BDM (20 mmol/L) in the same manner as melatonin treatment. Myocardial injury in the isolated hearts was assessed based on myocardial injury area, caspase-3 activity, and expressions of cytochrome C and cleaved caspase-3 proteins. Cardiac contracture was assessed using HE staining and by detecting lactate dehydrogenase (LDH) activity and the content of cardiac troponin I (cTnI) in the coronary outflow, measurement of left ventricular end-diastolic pressure (LVEDP) and electron microscopy. The content of ATP in the cardiac tissue was also determined. RESULTS: Compared with those in the control group, the isolated hearts in IR group showed significantly larger myocardial injury area and higher caspase-3 activity and the protein expressions of cytochrome C and cleaved caspase-3 with significantly increased LDH activity and cTnI content in the coronary outflow and elevated LVEDP at the end of reperfusion; HE staining showed obvious fractures of the myocardial fibers and the content of ATP was significantly decreased in the cardiac tissue; electron microscopy revealed the development of contraction bands. In the isolated hearts with IR, treatment with Mel or BDM significantly reduced the myocardial injury area, caspase-3 activity, and protein expressions of cytochrome C and cleaved caspase-3, obviously inhibited LDH activity, lowered the content of cTnI and LVEDP, reduced myocardial fiber fracture, and increased ATP content in the cardiac tissue. Both Mel and BDM inhibited the formation of contraction bands in the isolated hearts with IR injury. CONCLUSIONS Mel can alleviate myocardial IR injury in isolated rat hearts by inhibiting cardiac contracture, the mechanism of which may involve the upregulation of ATP in the cardiac myocytes to lessen the tear of membrane and reduce cell content leakage.
Animals ; Heart ; drug effects ; Male ; Melatonin ; pharmacology ; therapeutic use ; Muscle Contraction ; drug effects ; Myocardial Reperfusion Injury ; drug therapy ; Myocytes, Cardiac ; drug effects ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo investigate the expressions of P38 mitogen-activated protein kinases (P38 MAPK), JNK mitogen-activated protein kinases (JNK MAPK) and the therapeutical effects of melatonin in the renal tissue of acute acuteparaquat-induced rats.

METHODSSeventy-eight healthy adult Sprague-Dawley (SD) rats (39 male, 39 female) were randomly divided into three groups: (1) Control group (group A): 6 rats, (2) Poisoned group (group B): 36 rats, (3) Therapeutical group (group C): 36 rats. At 1, 3, 5, 7, 10 and 14 days after poisoning, six rats in Group B and group C were used to assess renal pathological changes and the expression of P38 MAPK, JNK MAPK in kidney were evaluated by immunohistochemistry.

RESULTSCompared with control group, the expression of P38MAPK in renal tissue of poisoned group significantly rose at the first day, reached the peak at the 10th day and afterwards decreased slowly. Expression of JNK MAPK reached the peak at the first day, and kept at relatively high levels up to the 14th day. Melatonin weakened markedly the expressions of P38 MAPK and JNK MAPK in renal tissue of acute acuteparaquat-induced rats.

CONCLUSIONP38 MAPK and JNK MAPK play an important role in renal injury of acute paraquat -poisoning rats. Melatonin takes a significant effect on the activation of them.

Animals ; Female ; JNK Mitogen-Activated Protein Kinases ; metabolism ; Kidney ; drug effects ; metabolism ; physiopathology ; Male ; Melatonin ; therapeutic use ; Paraquat ; poisoning ; Rats ; Rats, Sprague-Dawley ; p38 Mitogen-Activated Protein Kinases ; metabolism

INTRODUCTIONPain after wisdom teeth surgery can be moderate in severity and is compounded by preoperative anxiety in young patients. We studied the effect of melatonin premedication on postoperative pain and preoperative anxiety in patients undergoing wisdom teeth extractions.

METHODSThis randomised controlled trial recruited 76 patients at Khoo Teck Puat Hospital who were American Society of Anesthesiologists physical status I and II, aged 21 to 65 and scheduled to undergo elective extraction of all four wisdom teeth under general anaesthesia. Patients with a history of long-term use or allergy to melatonin were excluded. The patients received either 6 mg melatonin or a placebo 90 minutes before surgery. Visual analogue scale (VAS) scores at multiple time intervals for postoperative pain and preoperative anxiety, patient satisfaction and first-night sleep quality scores were obtained. Mixed-effects regression models were used for longitudinal analysis of VAS pain, anxiety and satisfaction scores.

RESULTSMaximum VAS scores for pain and anxiety were 18.6 ± 19.1 mm at 60 minutes postoperatively and 26.2 ± 23.4 mm at 90 minutes preoperatively, respectively. After adjusting for gender, female patients who received melatonin had a faster rate of reduction of VAS pain (p = 0.020) and anxiety scores (p = 0.003) over time compared to the placebo group. No such effect was demonstrated in male patients. There was no significant difference in sleep quality or satisfaction scores.

CONCLUSIONMelatonin use did not consistently contribute to pain and anxiety amelioration in all patients. Our study demonstrated a positive effect in female patients, suggestive of sexual dimorphism.

Adult ; Aged ; Anxiety ; drug therapy ; prevention & control ; Female ; Humans ; Male ; Melatonin ; therapeutic use ; Middle Aged ; Molar, Third ; surgery ; Pain Measurement ; Pain, Postoperative ; drug therapy ; Preanesthetic Medication ; methods ; Preoperative Period ; Prospective Studies ; Sex Factors ; Surgery, Oral ; methods ; Tooth Extraction ; Young Adult

OBJECTIVETo explore the effects of Kaixin Powder (, KXP) on melatonin receptor (MR) expression and (125)I-Mel binding affinity in a depression rat model.

METHODSSeventy-two male Wistar rats were divided into six groups: a blank control group, model group, ramelteon group, KXP high-dosage group (HKXP), medium-dosage group (MKXP) and low-dosage group (LKXP). To establish the depression model, all groups except the blank control group were singly housed and exposed to chronic unpredictable mild stress. Weight gain, sucrose consumption and the open-field test were used to evaluate induction of depression. KXP at 260, 130 and 65 mg/(kg•d) was also respectively administered to the rats in the HKXP, MKXP and LKXP groups for 21 days. Ramelteon [0.83 mg/(kg•d)] was given to the positive drug control group. An equivalent volume of physiological saline was given to the blank and model groups. The liquid chip method was used to measure the concentration of plasma melatonin (MT). Mel1a (MT1) and Mel1b (MT2) expression levels were determined by Western blotting. In addition, a radioactive ligand-binding assay was used to analyze the specific binding properties and dynamic characteristics between MR and (125)I-Mel.

RESULTSThe results of weight gain, sucrose consumption and the open-field test showed that our model successfully produced depressive symptoms and depressive-like behavior. The concentration of plasma MT in the model group decreased significantly at night but increased in the MKXP group (P<0.05). The HKXP group showed significantly increased expression of MT1 (P<0.05); however, the expression of MT2 in all groups exhibited no significant differences (P>0.05). The maximum binding capacity (B(max)) for specific binding between MR and 125I-Mel in the MKXP group was significantly higher than that in the model group (P<0.05), but no significant differences were found in the equilibrium dissociation constant (K(d)) of each group (P>0.05).

CONCLUSIONSKXP may have a similar effect as ramelteon. KXP improved depressive-like behavior by increasing the concentration of plasma MT and MT1 expression, thereby increasing three B(max) of MR to achieve the desired antidepressant effect.

Animals ; Brain ; drug effects ; metabolism ; pathology ; Depression ; blood ; drug therapy ; metabolism ; Disease Models, Animal ; Drinking Behavior ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Gene Expression Regulation ; drug effects ; Indenes ; Iodine Radioisotopes ; Male ; Melatonin ; blood ; metabolism ; Rats, Wistar ; Receptors, Melatonin ; genetics ; metabolism ; Weight Gain ; drug effects

BACKGROUNDPericytes, located on microvessels, help to maintain vascular stability and blood-brain barrier integrity. The influence of pericytes on microvessels after spinal cord injury (SCI) is less clear. Therefore, the aim of this study was to investigate whether pericytes took a protective effect on microvessels in melatonin-treated SCI.

METHODSC57BL/6 mice were randomly divided into three groups: sham group, SCI group, and melatonin group (n = 27 per group). Functional recovery was evaluated using the Basso Mouse Scale. Motor neurons were observed using hematoxylin and eosin staining. Pericyte coverage was analyzed using immunofluorescence. Permeability of blood-spinal cord barrier (BSCB) was assessed by administration of Evan's Blue. Protein levels of occludin, aquaporin-4 (AQP4), angiopoietin-1 (Ang1), intercellular cell adhesion molecule-1 (ICAM-1), Bcl-2, and Bax were determined using Western blotting. Mimicking the pathological conditions of SCI, melatonin-treated primary pericytes were subjected to oxygen-glucose deprivation/reperfusion (OGD/R). Secretion of Ang1 was analyzed using an enzyme-linked immunosorbent assay, and the expression of ICAM-1 was detected by immunofluorescence.

RESULTSMelatonin treatment improved locomotor functional outcome and rescued motor neurons. Pericyte coverage was significantly reduced after SCI; melatonin treatment alleviated the loss of pericyte coverage and rescued perfused microvessels 7 days after injury. The permeability of BSCB and loss of occludin were attenuated, and edema formation and upregulation of AQP4 were inhibited, after melatonin treatment. The expression of Ang1 and Bcl-2 was improved, while the expression of ICAM-1 and Bax was inhibited, in melatonin-treated SCI mice. Furthermore, the secretion of Ang1 was increased and the expression of ICAM-1 was inhibited in melatonin-treated pericytes after OGD/R.

CONCLUSIONSMelatonin ameliorated the loss of blood vessels and disruption of BSCB to exert a protective effect on SCI, which might be mediated by increased pericyte coverage. The upregulation of Ang1 in pericytes could inhibit inflammation and apoptosis to protect the microvessels.

Angiopoietin-1 ; metabolism ; Animals ; Enzyme-Linked Immunosorbent Assay ; Intercellular Adhesion Molecule-1 ; metabolism ; Male ; Melatonin ; pharmacology ; therapeutic use ; Mice ; Mice, Inbred C57BL ; Microvessels ; cytology ; Occludin ; metabolism ; Pericytes ; drug effects ; metabolism ; Random Allocation ; Spinal Cord Injuries ; drug therapy ; metabolism

AIM: Stress is recognized to precipitate anxiety and related psychological problems characterized by a wide range of biochemical and behavioral changes. The present study was carried out to investigate the protective effects of melatonin and buspirone, and their combination, against six hours immobilization stress-induced, anxiety-like behavioral and oxidative damage in mice. METHOD: Male Laca mice were pre-treated with melatonin (2.5, 5 mg·kg(-1)), buspirone (5, 10 mg·kg(-1)), and their combination for consecutive five days. On the 6(th) day, animals were immobilized for six hours, and thereafter various behavioral tests were performed followed by biochemical tests. RESULTS: Immobilization stress significantly impaired body weight, locomotor activity, and caused anxiety-like behavior, along with increased oxidative damage. Pretreatment with melatonin and buspirone significantly improved the loss in body weight and locomotor activity, attenuated anxiety-like behavior (in both the mirror chamber and plus maze performance tasks), further restored the levels of brain total proteins, and caused antioxidant-like effects, as evidenced by reduced lipid peroxidation, nitrite concentration, and restoration of reduced glutathione and catalase activity, as compared to control animals. In addition, combination of melatonin (2.5, 5 mg·kg(-1)) with buspirone (5 mg·kg(-1)) significantly potentiated their protective effects, as compared to their effects individually. CONCLUSION The present study suggests that melatonin potentiates the beneficial effect of buspirone against immobilization stress-induced, anxiety-like behavioral and oxidative damage in mice possibly by involving a serotonergic mechanism.
Animals ; Anti-Anxiety Agents ; pharmacology ; therapeutic use ; Antioxidants ; pharmacology ; therapeutic use ; Anxiety ; drug therapy ; Behavior, Animal ; drug effects ; Buspirone ; pharmacology ; therapeutic use ; Immobilization ; psychology ; Male ; Melatonin ; pharmacology ; therapeutic use ; Mice, Inbred Strains ; Oxidative Stress ; drug effects ; Stress, Psychological ; drug therapy

BACKGROUNDOur earlier studies indicate that melatonin inhibits the proliferation of prolactinoma and induces apoptosis of pituitary prolactin-secreting tumor in rats. Melatonin has also been shown to induce apoptosis and to reduce the production of ATP in breast tumor cells. This study analyzed the levels of the four mitochondrial respiratory complexes and the production of ATP and also the effects of melatonin treatment of prolactinoma.

METHODSIn the in vivo study, mitochondria were harvested from control pituitaries or prolactinoma collected from the pituitaries of melatonin- and 17-β-estradiol (E2)-treated male rats. In the in vitro study, prolactinoma cells mitochondria were harvested. Activities of the four mitochondrial respiratory complexes were assayed using fluorometer. ATP production of prolactinoma cells was estimated using bioluminescent methods.

RESULTSElevated levels of four mitochondrial respiratory complexes activities and ATP production were recorded in prolactinoma cells. Moreover, in both in vivo and in vitro studies, melatonin inhibited the activities of mitochondrial respiratory complexes and the production of ATP in prolactinoma cells.

CONCLUSIONSThere is a link between mitochondrial function increase and tumorigenesis. Melatonin induces apoptosis of pituitary prolactin-secreting tumor of rats via the induction of mitochondrial dysfunction and inhibition of energy metabolism.

Adenosine Triphosphate ; metabolism ; Animals ; Estradiol ; therapeutic use ; Male ; Melatonin ; therapeutic use ; Mitochondria ; drug effects ; metabolism ; Prolactin ; metabolism ; Prolactinoma ; drug therapy ; metabolism ; Rats ; Rats, Sprague-Dawley