Identification of potential inhibitors of Zika virus NS5 RNA-dependent RNA polymerase through virtual screening and molecular dynamic simulations

Zika virus (ZIKV) is one of the mosquito borne flavivirus with several outbreaks in past few years in tropical and subtropical regions. The non-structural proteins of flaviviruses are suitable active targets for inhibitory drugs due to their role in pathogenicity. In ZIKV, the non-structural protein 5 (NS5) RNA-Dependent RNA polymerase replicates its genome. Here we have performed virtual screening to identify suitable ligands that can potentially halt the ZIKV NS5 RNA dependent RNA polymerase (RdRp). During this process, we searched and screened a library of ligands against ZIKV NS5 RdRp. The selected ligands with significant binding energy and ligand-receptor interactions were further processed. Among the selected docked conformations, top five was further optimized at atomic level using molecular dynamic simulations followed by binding free energy calculations. The interactions of ligands with the target structure of ZIKV RdRp revealed that they form strong bonds within the active sites of the receptor molecule. The efficacy of these drugs against ZIKV can be further analyzed through in-vitro and in-vivo studies.     

Immunostimulatory DNA ameliorates experimental and spontaneous murine colitis

BACKGROUND & AIMS: Impaired mucosal barrier, cytokine imbalance, and dysregulated CD4(+) T cells play important roles in the pathogenesis of experimental colitis and human inflammatory bowel disease. Immunostimulatory DNA sequences (ISS-DNA) and their synthetic oligonucleotide analogs (ISS-ODNs) are derived from bacterial DNA, are potent activators of innate immunity at systemic and mucosal sites, and can rescue cells from death inflicted by different agents. We hypothesized that these combined effects of ISS-DNA could inhibit the damage to the colonic mucosa in chemically induced colitis and thereby limit subsequent intestinal inflammation. METHODS: The protective and the anti-inflammatory effect of ISS-ODN administration were assessed in dextran sodium sulfate-induced colitis and in 2 models of hapten-induced colitis in Balb/c mice. Similarly, these effects of ISS-ODN were assessed in spontaneous colitis occurring in IL-10 knockout mice. RESULTS: In all models of experimental and spontaneous colitis examined, ISS-ODN administration ameliorated clinical, biochemical, and histologic scores of colonic inflammation. ISS-ODN administration inhibited the induction of colonic proinflammatory cytokines and chemokines and suppressed the induction of colonic matrix metalloproteinases in both dextran sodium sulfate- and hapten-induced colitis. CONCLUSIONS: As the colon is continuously exposed to bacterial DNA, these findings suggest a physiologic, anti-inflammatory role for immunostimulatory DNA in the GI tract. Immunostimulatory DNA deserves further evaluation for the treatment of human inflammatory bowel disease.     

Occurrence of a mosquito vector in bird houses: Developmental consequences and potential epidemiological implications

Even with continuous vector control, dengue is still a growing threat to public health in Southeast Asia. Main causes comprise difficulties in identifying productive breeding sites and inappropriate targeted chemical interventions. In this region, rural families keep live birds in backyards and dengue mosquitoes have been reported in containers in the cages. To focus on this particular breeding site, we examined the capacity of bird fecal matter (BFM) from the spotted dove, to support Aedes albopictus larval growth. The impact of BFM larval uptake on some adult fitness traits influencing vectorial capacity was also investigated. In serial bioassays involving a high and low larval density (HD and LD), BFM and larval standard food (LSF) affected differently larval development. At HD, development was longer in the BFM environment. There were no appreciable mortality differences between the two treatments, which resulted in similar pupation and adult emergence successes. BFM treatment produced a better gender balance. There were comparable levels of blood uptake and egg production in BFM and LSF females at LD; that was not the case for the HD one, which resulted in bigger adults. BFM and LSF females displayed equivalent lifespans; in males, this parameter was shorter in those derived from the BFM/LD treatment. Taken together these results suggest that bird defecations successfully support the development of Ae. albopictus. Due to their cryptic aspects, containers used to supply water to encaged birds may not have been targeted by chemical interventions.     

Notch signaling regulates cardiomyocyte proliferation during zebrafish heart regeneration

The human heart’s failure to replace ischemia-damaged myocardium with regenerated muscle contributes significantly to the worldwide morbidity and mortality associated with coronary artery disease. Remarkably, certain vertebrate species, including the zebrafish, achieve complete regeneration of amputated or injured myocardium through the proliferation of spared cardiomyocytes. Nonetheless, the genetic and cellular determinants of natural cardiac regeneration remain incompletely characterized. Here, we report that cardiac regeneration in zebrafish relies on Notch signaling. Following amputation of the zebrafish ventricular apex, Notch receptor expression becomes activated specifically in the endocardium and epicardium, but not the myocardium. Using a dominant negative approach, we discovered that suppression of Notch signaling profoundly impairs cardiac regeneration and induces scar formation at the amputation site. We ruled out defects in endocardial activation, epicardial activation, and dedifferentiation of compact myocardial cells as causative for the regenerative failure. Furthermore, coronary endothelial tubes, which we lineage traced from preexisting endothelium in wild-type hearts, formed in the wound despite the myocardial regenerative failure. Quantification of myocardial proliferation in Notch-suppressed hearts revealed a significant decrease in cycling cardiomyocytes, an observation consistent with a noncell autonomous requirement for Notch signaling in cardiomyocyte proliferation. Unexpectedly, hyperactivation of Notch signaling also suppressed cardiomyocyte proliferation and heart regeneration. Taken together, our data uncover the exquisite sensitivity of regenerative cardiomyocyte proliferation to perturbations in Notch signaling.When blood flow to a segment of the human heart becomes acutely interrupted, the hypoxic muscle suffers irreparable damage termed an acute myocardial infarction (1). An important public health concern, myocardial infarctions cause significant morbidity and mortality worldwide (2). As one of the least regenerative organs in the human body, the heart replaces the infarcted myocardium with noncontractile scar tissue instead of new muscle. As a result, the spared myocardium carries an increased hemodynamic burden that often leads to adverse ventricular remodeling and congestive heart failure. Therefore, the development of novel therapeutic strategies to stimulate human cardiac regeneration remains a top priority.Unlike mammals, adult zebrafish completely regenerate their hearts following amputation, cryoinjury, hypoxia/reoxygenation injury, or genetic ablation of cardiomyocytes (3–11). Lineage tracing studies have demonstrated that new cardiomyocytes arise by proliferation of partially dedifferentiated cardiomyocytes spared from injury (12, 13). Specifically, cardiomyocytes in the compact muscular layer proximal to the wound break down their sarcomeres, activate gata4 regulatory sequences, and initiate cell cycling with cytokinesis (12, 13). Interestingly, 1-d-old neonatal mice also achieve heart regeneration through cardiomyocyte proliferation following amputation injury (14). However, this endogenous regenerative potential is dampened by neonatal day 7 as cardiomyocytes exit the cell cycle through the up-regulation of meis1 and miR-15 (15, 16). Ultimately, the natural capacity for cardiac regeneration exhibited by adult zebrafish and neonatal mice suggests that the human heart could be stimulated to regenerate if the cellular and genetic determinants of cardiomyocyte proliferation were fully elucidated.Although adult mammalian cardiomyocytes have long been considered quiescent, recent stable isotope labeling studies in mice and humans have uncovered bona fide cardiomyocyte cell division during adult life (17–19). Moreover, following experimental myocardial infarction in mice, ∼3% of cardiomyocytes in the peri-infarct region arise through cardiomyocyte proliferation (19). These data demonstrate that, although insufficient to restore heart function, cardiomyocyte renewal does occur in the adult mammalian heart. These observations highlight the potential of augmenting endogenous cardiomyocyte proliferation as an effective treatment for myocardial infarction.The Notch signaling pathway plays fundamental roles in myriad developmental and regenerative processes (20). A previous study reported that partial amputation of the zebrafish ventricle stimulates expression of the Notch signaling components deltaC and notch1b (8), but the functional significance of this observation remains unexplored. Here, we report that amputation injury stimulates expression of three Notch receptors specifically in the endocardium and epicardium. Furthermore, Notch pathway suppression impaired the regeneration of new muscle and induced scar formation at the site of injury. Activation of the endocardium, epicardium, and gata4 cis-regulatory elements in compact myocardium were grossly unaffected by Notch suppression, but cardiomyocyte proliferation was significantly impaired. Unexpectedly, ubiquitous Notch pathway activation also inhibited cardiomyocyte proliferation and cardiac regeneration. These studies demonstrate that cardiomyocyte proliferative renewal is exquisitely sensitive to perturbations in Notch signaling.