Muhammed Yayla

A Review of Melatonin, Its Receptors and Drugs.

After a Turkish scientist took Nobel Prize due to his contributions to understand clock genes, melatonin, closely related to these genes, may begin to shine. Melatonin, a hormone secreted from the pineal gland at night, plays roles in regulating sleep-wake cycle, pubertal development and seasonal adaptation. Melatonin has antinociceptive, antidepressant, anxiolytic, antineophobic, locomotor activity-regulating, neuroprotective, anti-inflammatory, pain-modulating, blood pressure-reducing, retinal, vascular, anti-tumor and antioxidant effects. It is related with memory, ovarian physiology, and osteoblast differentiation. Pathologies associated with an increase or decrease in melatonin levels are summarized in the review. Melatonin affects by four mechanisms: 1) Binding to melatonin receptors in plasma membrane, 2) Binding to intracellular proteins such as calmoduline, 3) Binding to Orphan nuclear receptors, and 4) Antioxidant effect. Receptors associated with melatonin are as follows: 1) Melatonin receptor type 1a: MT1 (on cell membrane), 2) Melatonin receptor type 1b: MT2 (on cell membrane), 3) Melatonin receptor type 1c (found in fish, amphibians and birds), 4) Quinone reductase 2 enzyme (MT3 receptor, a detoxification enzyme), 5) RZR/RORα: Retinoid-related Orphan nuclear hormone receptor (with this receptor, melatonin binds to the transcription factors in nucleus), and 6) GPR50: X-linked Melatonin-related Orphan receptor (it is effective in binding of melatonin to MT1). Melatonin agonists such as ramelteon, agomelatine, circadin, TIK-301 and tasimelteon are introduced and side effects will be discussed. In conclusion, melatonin and related drugs is a new and promising era for medicine. Melatonin receptors and melatonin drugs will take attention with greater interest day by day in the future.

The Effects of Testosterone on Intestinal Ischemia/Reperfusion in Rats

ABSTRACT Ischemic injury to the gut is believed to occur in many serious clinical conditions. Our aim was to investigate the postischemia/reperfusion (I/R) effects of exogenously administered testosterone on the intestines of normal and orchiectomized rats.Forty-eight rats were divided into eight groups of six animals: (1) Sham-operated control group; (2) Sham-operated + testosterone-treated group; (3) I/R group: Rats were subjected to the surgical procedures and underwent intestinal ischemia for 60 min followed by reperfusion for 60 min; (4) I/R + testosterone-treated group: Rats were subjected to the surgical procedures and received testosterone 100 mg/kg (i.p.); (5) I/R + orchiectomy group: Rats were subjected to the surgical procedures as well as orchiectomy; (6) orchiectomy group: Rats were subjected to the surgical procedures as well as orchiectomy; (7) orchiectomy + testosterone-treated group: Rats were subjected to the surgical procedures as well as orchiectomy and received testosterone 100 mg/kg (i.p.); and (8) I/R + orchiectomy + testosterone-treated group. The histological findings of this study paralleled the observed degree of lipid peroxidation (LPO) and protein oxidation. Intestinal mucosal injury was extensive in the I/R, I/R + orchiectomy, and I/R + orchiectomy + testosterone groups, but was less in the I/R + testosterone group. Histopathological injury also paralleled the degree of oxidative stress. Apoptotic enterocytes were more numerous in the I/R, I/R + orchiectomy, and I/R + orchiectomy + testosterone groups. Administration of testosterone in the presence of testes significantly protected intestinal tissue against I/R mucosal injuries, while administration of testosterone in the absence of testes did not significantly protect intestinal tissue against I/R mucosal injuries.

Development and validation of UFLC-MS/MS method for determination of bosentan in rat plasma.

A rapid, simple and sensitive UFLC-MS/MS method was developed and validated for the determination of bosentan in rat plasma using etodolac as an internal standard (IS) after liquid-liquid extraction with diethyl ether-chloroform (4:1, v/v). Bosentan and IS were detected using electrospray ionization in positive ion multiple reaction monitoring mode by monitoring the transitions m/z 551.90→201.90 and 288.20→172.00, respectively. Chromatographic separation was performed on the inertsil ODS-4 column with a gradient mobile phase, which consisted of 0.1% acetic acid with 5mM ammonium acetate in water for solvent A and 5mM ammonium acetate in acetonitrile-methanol (50:50, v/v) for solvent B at a flow rate of 0.3mL/min. The method was sensitive with 0.5ng/mL as the lower limit of quantitation (LLOQ) and the standard calibration curve for bosentan was linear (r>0.997) over the studied concentration range (0.5-2000ng/mL). The proposed method was fully validated by determining specificity, linearity, LLOQ, precision and accuracy, recovery, matrix effect and stability. The validated method was successfully applied to plasma samples obtained from rats.

The Ocular Endothelin System: A Novel Target for the Treatment of Endotoxin-Induced Uveitis With Bosentan

PURPOSE We compared the anti-inflammatory effects of bosentan and dexamethasone in endotoxin-induced uveitis (EIU). METHODS Endotoxin-induced uveitis was induced by subcutaneous injection of lipopolysaccharide (LPS, 200 μg) in Wistar rats. Rats were divided randomly into 10 groups (n = 6). Bosentan at doses of 50 and 100 mg/kg were administered orally 1 hour before and 12 hours after LPS injection, and dexamethasone was administered by intraperitoneally 30 minutes before and 30 minutes after LPS injection at a dose of 1 mg/kg. Data were collected at two time points for each control and treatment; animals were killed at either 3 or 24 hours after LPS injection. Histopathologic evaluation and aqueous humour measurements of TNF-α level were performed, and endothelin-1 (ET-1), inducible nitric oxide synthase (iNOS), and endothelin receptor A and B (EDNRA and B) expression were analyzed. RESULTS The group treated with 100 mg/kg bosentan at 24 hours displayed significantly milder uveitis and fewer inflammatory cells compared to LPS-injected animals, and there were similar findings in the dexamethasone-treated group at 24 hours. The TNF-α levels in the dexamethasone treatment group were lower than those in the LPS-induced uveitis control group (P < 0.05); however, there was no difference between the dexamethasone and bosentan treatment groups at 3 and 24 hours after LPS administration. Bosentan treatment at doses of 50 and 100 mg/kg significantly decreased iNOS expression compared to LPS-injected animals (P < 0.001). The ET-1 expression was suppressed significantly by bosentan and dexamethasone at 3 and 24 hours after LPS administration (P < 0.001). The EDNRA expression in the bosentan treatment groups was statistically significantly lower than that in the LPS-induced uveitis control group at 3 and 24 hours after LPS administration (P < 0.05). CONCLUSIONS Bosentan reduces intraocular inflammation and has similar effects as dexamethasone in a rat model of EIU.

Blocking of urotensin receptors as new target for treatment of carrageenan induced inflammation in rats

This study investigated possible role of U-II and its receptor expression in inflammation by using UTR agonist and antagonist in carrageenan induced acute inflammation. Rats were divided into 5 groups as (1) Healthy control, (2) Carrageenan control, (3) Carrageenan +Indomethacin 20mg/kg, orally, (4) Carrageenan +AC7954 (U-II receptor agonist, intraperitoneally) 30mg/kg and (5) Carrageenan +SB657510 (UTR antagonist, intraperitoneally) 30mg/kg. 1h after drug administration, carrageenan was injected. At the 3rd hour after carrageenan injection, agonist produced no effect while antagonist 63% anti-inflammatory effect respectively. UTR and UT-II expression increased in carrageenan induced paw tissue. Antagonist administration prevented the decrease in an antioxidant system and also capable to decrease TNF-α and IL-6 mRNA expressions. This study showed the role of urotensin II receptors in the physiopathogenesis of acute inflammatory response that underlying many diseases accompanied by inflammation.

Is There a Relationship between Obstructive Sleep Apnea Syndrome Severity and Nesfatin-1?

Background: Obstructive sleep apnea syndrome (OSAS) and obesity frequently occur together. The relationship between increased appetite and obesity is well known; however, despite existing knowledge about the relationship between OSAS and obesity, it is not fully understood. Objectives: This study aimed to evaluate the relationship between OSAS and the appetite-suppressing hormone nesfatin-1 independent of body mass index (BMI). Methods: A total of 134 cases were included in the study; 102 with OSAS (OSAS group) and 32 healthy controls (control group). All cases underwent polysomnography, and nesfatin-1 levels were determined. Results: Nesfatin-1 levels were significantly lower in the OSAS group compared to the control group (3,776.5 ± 204.8 and 4,056.2 ± 101.5 pg/ml, respectively; p < 0.001). In addition, there was a statistically significant negative correlation between nesfatin-1 and the apnea hypopnea index (r = -0.543; p < 0.001). The statistically significant relationship persisted after adjusting for confounding intergroup factors such as age, gender and BMI (p < 0.001). In the OSAS group, there was a statistically significant correlation between nesfatin-1 and neck circumference (r = -0.304; p = 0.02) but not between nesfatin-1 and BMI and waist circumference. There was no statistically significant difference in nesfatin-1 levels between the sexes. Conclusion: OSAS patients have lower nesfatin-1 levels compared to controls, and a greater nesfatin-1 deficit corresponds to an increased severity of OSAS and an increased neck circumference. Replacement therapy may be a potential treatment for obese OSAS patients who have lower nesfatin-1 levels, which may have additional benefits through appetite suppression and weight loss.

The Role of Urotensin Receptors in the Paracetamol-Induced Hepatotoxicity Model in Mice: Ameliorative Potential of Urotensin II Antagonist

We aimed to evaluate the possible protective effect of a UTR antagonist and to determine the effect of the antagonist on ALT and AST levels in serum, the mRNA expression level of UTR, tumour necrosis factor‐alpha (TNF‐α) and IL‐1β and SOD activity, GSH and MDA levels in liver tissues, which are important mediators or markers for the hepatotoxicity animal model in mice. Animals fasted overnight and were divided into seven equal groups (n = 12). The first group was the healthy group (administered 0.1% DMSO intraperitoneally). Group 2 received only paracetamol (PARA) (administered orally at a dosage of 300 mg/kg). Groups 3 and 4 were treated with only AGO (AC7954, UTR agonist) 15 and 30 mg/kg intraperitoneally, respectively. Groups 5 and 6 were treated with only ANTA (SB657510, UTR antagonist) 30 and 60 mg/kg intraperitoneally, respectively. Group 7 was treated with AGO 30 mg/kg and ANTA 60 mg/kg intraperitoneally. One hour after the pre‐treatment drugs were administered, groups 3 through 7 were given PARA. After the experimental period, the mice were killed 6 and 24 hr after PARA was administered. Antagonist administration significantly decreased the ALT and AST levels, while agonist administration did not. In addition, SOD activity and GSH levels increased, and the MDA level decreased with the pre‐treatment of two antagonist doses. The increased UTR gene expression through PARA was significantly lower in both doses of the antagonist groups at 24 hr when compared with the agonist and PARA groups. This study showed that UTR antagonists have hepatoprotective and anti‐inflammatory effects on high‐dose PARA‐induced hepatotoxicity in mice.

Does bosentan protect diabetic brain alterations in rats? The role of endothelin-1 in the diabetic brain.

Diabetes mellitus (DM) is a major problem all over the world, affecting more people in recent years. Individuals with diabetes are more prone to disease than non‐diabetics, especially vascular complications. The aim of this study was to examine the roles of the endothelin (ET)‐1 in brain damage formed in a streptozocin (STZ)‐induced diabetes model, and the effect of bosentan, which is the non‐specific ET1 receptor blocker in the prevention of the diabetes‐induced brain damage. To examine the effects of bosentan (50 mg/kg and 100 mg/kg) in this study, the rats were given the drug for 3 months. The rats were divided into four groups: the sham group (n = 10), the diabetic control group (n = 10), the group of diabetic rats given bosentan 50 mg/kg (n = 10) and the group of diabetic rats given bosentan 100 mg/kg (n = 10). Diabetes was induced in the rats by STZ (60 mg/kg i.p.). On day 91, all rats were killed. Brain tissues of the rats were measured by molecular, biochemical and histopathological methods. Antioxidant levels in the therapy groups were observed as quite near to the values in the healthy group. In this study, while the brain eNOS levels in the diabetic groups decreased, the ET1 and iNOS levels were found to be increased. However, in the diabetes group, hippocampus and cerebellum, pericellular oedema and a number of neuronal cytoretraction were increased in neuropiles, whereas these results were decreased in the therapy group. Based on all of these results, ET1 will not be ignored in diabetes‐induced cerebral complications.

The role of endothelin-1 and endothelin receptor antagonists in allergic rhinitis inflammation: ovalbumin-induced rat model.

OBJECTIVE Desloratadine is a biologically active metabolite of loratadine which is indicated for the treatment of allergic rhinitis. Bosentan is a dual endothelin receptor antagonist used to treatment of pulmonary artery hypertension (PAH). In this study, we aimed to determine the role of endothelins in allergic rhinitis (AR) and the effects of endothelin receptor antagonists in AR rat models through comparison with desloratadine. METHODS In total, 20 adult Sprague-Dawley rats were used in this study. An ovalbumin-induced allergic rhinitis model was formed in three study groups except for the control group. Bosentan (100 mg/kg/day) was given to the bosentan-treated group for 7 days and desloratadine (10 mg/kg/day) was administered to the antihistaminic-treated group for 7 days. Nasal symptom scorings and histopathological examinations of the nasal tissues were carried out. Serum IgE levels and ET-1 and TNF-alpha mRNA expression levels were analysed. Between group comparisons for nasal symptoms, histopathological analysis, and molecular analyses were performed with a one-way ANOVA and Duncans multiple comparison tests. Significance was accepted at p smaller than 0.05. RESULTS Bosentan inhibited nasal symptom more significantly than desloratadine. The IgE level, ET-1 and TNF-alpha mRNA expression levels statistically increased in the allergic rhinitis group when compared to other groups. Conversely, the bosentan-treatment group showed a significant recovery from the same parameters. The deterioration in histopathological parameters reached the highest levels in the allergic rhinitis group. The histopathological findings were close to those of the control group in the bosentan and antihistaminic-treated group. CONCLUSIONS ET-1 is one of the mediators that impact AR development and ET-1 antagonists can be useful for symptom control and for decreasing allergic inflammation in AR patients.

L-carnitine alleviates sciatic nerve crush injury in rats: functional and electron microscopy assessments.

Several studies have demonstrated that L-carnitine exhibits neuroprotective effects on injured sciatic nerve of rats with diabetes mellitus. It is hypothesized that L-carnitine exhibits neuroprotective effects on injured sciatic nerve of rats. Rat sciatic nerve was crush injured by a forceps and exhibited degenerative changes. After intragastric administration of 50 and 100 mg/kg L-carnitine for 30 days, axon area, myelin sheath area, axon diameter, myelin sheath diameter, and numerical density of the myelinated axons of injured sciatic nerve were similar to normal, and the function of injured sciatic nerve also improved significantly. These findings suggest that L-carnitine exhibits neuroprotective effects on sciatic nerve crush injury in rats.