Jashoman Banerjee

Melatonin prevents hypochlorous acid‐induced alterations in microtubule and chromosomal structure in metaphase‐II mouse oocytes

Abstract:  Hypochlorous acid (HOCl) is generated by myeloperoxidase, using chloride and hydrogen peroxide as substrates. Here we demonstrate that HOCl alters metaphase‐II mouse oocyte microtubules and chromosomal (CH) alignment which can be prevented by melatonin. Metaphase‐II mouse oocytes, obtained commercially, were grouped as: control, melatonin (150, 200 nmol/mL), HOCl (10, 20, 50, and 100 nmol/mL), and HOCl (50 nmol/mL) pretreated with 150 and 200 nmol/mL of melatonin. Microtubule and CH alignment was studied utilizing an indirect immunofluorescence technique and scored by two observers. Pearson chi‐square test and Fisher’s exact test were used to compare outcomes between controls and treated groups and also among each group. Poor scores for the spindle and chromosomes increased significantly at 50 nmol/mL of HOCl (P < 0.001). Oocytes treated with melatonin only at 150 and 200 nmol/mL showed no changes; significant differences (P < 0.001) were observed when oocytes exposed to 50 nmol/mL of HOCl were compared to oocytes pretreated with 200 nmol/mL melatonin. Fifty percent of the oocytes demonstrated good scores, both in microtubule and CH alterations, when pretreated with melatonin at 150 nmol/mL compared to 0% in the HOCl‐only group. HOCl alters the metaphase‐II mouse oocyte spindle and CH alignment in a dose‐dependant manner, which might be a potential cause of poor oocyte quality (e.g., in patients with endometriosis). Melatonin prevented the HOCl‐mediated spindle and CH damage, and therefore, may be an attractive therapeutic option to prevent oocyte damage in endometriosis or inflammatory diseases where HOCl levels are known to be elevated.

The reaction of HOCl and cyanocobalamin: Corrin destruction and the liberation of cyanogen chloride

Overproduction of hypochlorous acid (HOCl) has been associated with the development of a variety of disorders such as inflammation, heart disease, pulmonary fibrosis, and cancer through its ability to modify various biomolecules. HOCl is a potent oxidant generated by the myeloperoxidase-hydrogen peroxide-chloride system. Recently, we have provided evidence to support the important link between higher levels of HOCl and heme destruction and free iron release from hemoglobin and RBCs. Our current findings extend this work and show the ability of HOCl to mediate the destruction of metal-ion derivatives of tetrapyrrole macrocyclic rings, such as cyanocobalamin (Cobl), a common pharmacological form of vitamin B12. Cyanocobalamin is a water-soluble vitamin that plays an essential role as an enzyme cofactor and antioxidant, modulating nucleic acid metabolism and gene regulation. It is widely used as a therapeutic agent and supplement, because of its efficacy and stability. In this report, we demonstrate that although Cobl can be an excellent antioxidant, exposure to high levels of HOCl can overcome the beneficial effects of Cobl and generate proinflammatory reaction products. Our rapid kinetic, HPLC, and mass spectrometric analyses showed that HOCl can mediate corrin ring destruction and liberate cyanogen chloride (CNCl) through a mechanism that initially involves α-axial ligand replacement in Cobl to form a chlorinated derivative, hydrolysis, and cleavage of the phosphonucleotide moiety. Additionally, it can liberate free Co, which can perpetuate metal-ion-induced oxidant stress. Taken together, these results are the first report of the generation of toxic molecular products through the interaction of Cobl with HOCl.

The Defensive Role of Cumulus Cells Against Reactive Oxygen Species Insult in Metaphase II Mouse Oocytes.

We investigated the ability of reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), hydroxyl radical (·OH), and hypochlorous acid (HOCl), to overcome the defensive capacity of cumulus cells and elucidate the mechanism through which ROS differentially deteriorate oocyte quality. Metaphase II mouse oocytes with (n = 1634) and without cumulus cells (n = 1633) were treated with increasing concentration of ROS, and the deterioration in oocyte quality was assessed by the changes in the microtubule morphology and chromosomal alignment. Oocyte and cumulus cell viability and cumulus cell number were assessed by indirect immunofluorescence, staining of gap junction protein, and trypan blue staining. The treated oocytes showed decreased quality as a function of increasing concentrations of ROS when compared to controls. Cumulus cells show protection against H2O2 and ·OH insult at lower concentrations, but this protection was lost at higher concentrations (>50 μmol/L). At higher H2O2 concentrations, treatment dramatically influenced the cumulus cell number and viability with resulting reduction in the antioxidant capacity making the oocyte more susceptible to oxidative damage. However, cumulus cells offered no significant protection against HOCl at any concentration used. In all circumstances in which cumulus cells did not offer protection to the oocyte, both cumulus cell number and viability were decreased. Therefore, the deterioration in oocyte quality may be caused by one or more of the following: a decrease in the antioxidant machinery by the loss of cumulus cells, the lack of scavengers for specific ROS, and/or the ability of the ROS to overcome these defenses.

Impact of hydrogen peroxide driven Fenton reaction on mouse oocyte quality

Here we show that hydroxyl radical ((•)OH) generated through the Fenton reaction alters metaphase-II mouse oocyte microtubules (MT) and chromosomal alignment (CH). Metaphase-II mouse oocytes, obtained commercially, were grouped as follows: control, hydrogen peroxide (H2O2), Fe(II), and combined (Fe(II) +H2O2) treatments. After 7-10 min of incubation at 37 °C, MT and CH were evaluated on fixed and stained oocytes and scored by two blinded observers. Pearson χ(2) test and Fisher exact test were used to compare outcomes between controls and treated groups and also among the treated groups. Our results showed that poor scores for MT and CH increased significantly in oocytes treated with a combination of H2O2 and Fe(II) (p<0.001); oocytes treated with H2O2 alone or Fe(II) alone showed no or few changes compared to control. Comparison of oocyte groups that received increasing concentrations of H2O2 and a fixed amount of Fe(II) showed that 70-80% demonstrated poor scores in both MT and CH when pretreated with 5 μM H2O2, and this increased up to 90-100% when treated with 10-20 μM H2O2. Hydroxyl radical generated by H2O2-driven Fenton reaction deteriorates the metaphase-II mouse oocyte spindle and CH alignment, which is thought to be a potential cause of poor oocyte quality. Thus, free iron and/or ROS scavengers could attenuate the (•)OH-mediated spindle and chromosomal damage, thereby serving as a possible approach for further examination as a therapeutic option in inflammatory states.

IL-6 and Mouse Oocyte Spindle

Interleukin 6 (IL-6) is considered a major indicator of the acute-phase inflammatory response. Endometriosis and pelvic inflammation, diseases that manifest elevated levels of IL-6, are commonly associated with higher infertility. However, the mechanistic link between elevated levels of IL-6 and poor oocyte quality is still unclear. In this work, we explored the direct role of this cytokine as a possible mediator for impaired oocyte spindle and chromosomal structure, which is a critical hurdle in the management of infertility. Metaphase-II mouse oocytes were exposed to recombinant mouse IL-6 (50, 100 and 200 ng/mL) for 30 minutes and subjected to indirect immunofluorescent staining to identify alterations in the microtubule and chromosomal alignment compared to untreated controls. The deterioration in microtubule and chromosomal alignment were evaluated utilizing both fluorescence and confocal microscopy, and were quantitated with a previously reported scoring system. Our results showed that IL-6 caused a dose-dependent deterioration in microtubule and chromosomal alignment in the treated oocytes as compared to the untreated group. Indeed, IL-6 at a concentration as low as 50 ng/mL caused deterioration in the spindle structure in 60% of the oocytes, which increased significantly (P<0.0001) as IL-6 concentration was increased. In conclusion, elevated levels of IL-6 associated with endometriosis and pelvic inflammation may reduce the fertilizing capacity of human oocyte through a mechanism that involves impairment of the microtubule and chromosomal structure.

Melatonin Can Mediate Its Vascular Protective Effect by Modulating Free Iron Level by Inhibiting Hypochlorous Acid–Mediated Hemoprotein Heme Destruction

To the Editor: A recent interesting study by Rezzani et al in Hypertension 1 has shown that melatonin treatment can reduce blood pressure in spontaneously hypertensive rats. The authors attributed this role of melatonin to its capacity to function as an antioxidant, as well as a vasodilator, by increasing the availability of NO. In response to this article, van der Zwan et al2 proposed that melatonins blood pressure modulating effect is not only attributed to its capacity as a potential antioxidant but also through its ability to inhibit myeloperoxidase (MPO) activity in vascular tissue. In our opinion, both of these two proposed mechanisms seem to be valid, but melatonins role in controlling vascular phenomena is not limited to these …

Missing IUD and utilization of fluoroscopy for management: a case report

INTRODUCTION A missing intrauterine device (IUD) poses challenges in diagnosis and treatment. Extrauterine placement of IUDs may cause difficulty in localization. We report a case where use of fluoroscopy just prior to laparoscopic intervention to remove the missing IUD was beneficial. CASE This case report involves a 35-year-old woman who was diagnosed with a missing thread 2 years after insertion of a levonorgestrel IUD (Mirena). Initial diagnostic workup consisting of abdominal X-ray, an ultrasound and diagnostic laparoscopy failed to localize the IUD. We performed an office pelvic ultrasound which confirmed that an IUD was present but could not specifically localize the IUD in the pelvic or abdominal cavity. Hence, we utilized fluoroscopy just prior to laparoscopy to localize and remove the missing device and allow its removal. CONCLUSION Various imaging modalities aid in detecting a missing IUD, but proper selection of fluoroscopy helped to localize extrauterine placement of an IUD device. We suggest that utilization of this imaging method just prior to laparoscopy may be of value in selected cases.