In-silico genomic characterization of Staphylococcus haemolyticus on a global scale: lineages, resistome, and virulome

BACKGROUND

Staphylococcus haemolyticus belongs to the Coagulase-Negative Staphylococci (CoNS), exhibiting the highest levels of antibiotic resistance within this group of bacteria. This species has been increasingly implicated in nosocomial and animal infections worldwide, with a prevalence of methicillin-resistant Staphylococcus haemolyticus (MRSH). Most information about this organism comes from regional analyzes or with the absence of typing data, thus not revealing the real role of S. haemolyticus strains in world public health.

METHODS

Here, we performed an enhanced global epidemiological analysis considering all available S. haemolyticus genomes from all continents, including genomes of nosocomial, environmental, and animal origin (n = 310). Furthermore, we added original genomic information from a clinical MRSH from the Brazilian Amazon region. The resistome and virulome of the genomes were associated with their mobilome, being inferred based on the presence of specific genes and databases such as CARD, VFDB, and PlasmidFinder, respectively.

RESULTS

Phylogenetic analysis revealed three main groups, the main one covering most of the clinical clonal complex 3 (CC3) genomes in the world. The virulome of some genomes in this cluster showed the complete capsule operon (capA-capM). Importantly, this virulome trait could be associated with the mobilome, since the capsule operon, as well as a whole set of genes of the type VII secretion system, were observed in plasmids. In addition, the resistome of the main cluster (CC3) was larger, characterized mainly by the presence of the mecA gene, in addition to a set of other genes (aad, aac-aph, aph, erm), contrasting with the poor resistome of the other two clusters. Several insertion sequences were identified, some of them linked to specific clusters, and resistance genes, such as the rare cfrA (IS257).

CONCLUSIONS

Therefore, successful lineages of CC3 S. haemolyticus causing human infections are widespread worldwide, raising concern about the impact of this scenario on public health.

Osteopontin regulates proliferation, migration, and survival of astrocytes depending on their activation phenotype

The glycoprotein osteopontin is highly upregulated in central nervous system (CNS) disorders such as ischemic stroke. Osteopontin regulates cell growth, cell adhesion, homeostasis, migration, and survival of various cell types. Accordingly, osteopontin is considered an essential regulator of regeneration and repair in the ischemic milieu. Astrocytes are the most abundant cells in the CNS and play significant roles in health and disease. Astrocytes are involved in homeostasis, promote neuroprotection, and regulate synaptic plasticity. Upon activation, astrocytes may adopt different phenotypes, termed A1 and A2. The direct effects of osteopontin on astrocytes, especially in distinct activation states, are yet unknown. The current study aimed to elucidate the impact of osteopontin on resting and active astrocytes. We established an inflammatory in vitro model of activated (A1) primary astrocytes derived from neonatal wistar rats by exposure to a distinct combination of proinflammatory cytokines. To model ischemic stroke in vitro, astrocytes were subjected to oxygen and glucose deprivation (OGD) in the presence or absence of osteopontin. Osteopontin modulated the activation phenotype by attenuating A1- and restoring A2-marker expression without compromising the active astrocytes' immunocompetence. Osteopontin promoted the proliferation of active and the migration of resting astrocytes. Following transient OGD, osteopontin mitigated the delayed ongoing death of primary astrocytes, promoting their survival. Data suggest that osteopontin differentially regulates essential functions of resting and active astrocytes and confirm a significant regulatory role of osteopontin in an in vitro ischemia model. Furthermore, the data suggest that osteopontin constitutes a promising target for experimental therapies modulating neuroregeneration and repair.

Porous organic cage for enantiomeric fluorescence recognition of amino acid and hydroxy acid

A new method based on the enantioselective recognition of porous organic cages CC3-R was established for the first time. Porous organic cages are widely used for separation, adsorption and host-guest interaction sensing, but are rarely used for fluorescence sensing. Based on the inherent chiral environment of CC3-R and the inherent fluorescence properties of the organic ligands constituting the cage, when different chiral monomers diffuse into the cage, different effects occur to produce changes in fluorescence. We found for the first time that the fluorescence of CC3-R can be enhanced and quenched by tyrosine and mandelic acid, respectively, and that different chiral monomers are enhanced or quenched differently at the same concentration. Unlike the chiral recognition of other composite luminescent materials, the chiral porous organic cage not only utilizes its own host-guest effect for chiral recognition, but also utilizes the organic ligands constituting the cage for luminescence recognition. This work provides an alternative method to accomplish chiral recognition other than chromatography, that is using porous organic cages (POC), but it can show the advantages of simplicity, low cost and high sensitivity. We believe this work could provide valuable thoughts in the exploration of POC in chiral recognition as new FL probes for the future.

MiR-139-5p inhibits HGTD-P and regulates neuronal apoptosis induced by hypoxia-ischemia in neonatal rats

Human growth transformation dependent protein (HGTD-P) is a newly identified protein that promotes neuronal apoptosis in hypoxia-ischemia brain damage (HIBD) in neonatal rats. However, the mechanisms regulating HGTD-P expression are not clear. Here we describe microRNAs targeted to HGTD-P and examine their effects on regulating neuronal apoptosis in HIBD. We use samples from cultured neurons after oxygen-glucose deprivation (OGD) and postnatal day 10 rat brains after hypoxia-ischemia (HI). RT-PCR, Western blotting, and immunostaining are used to detect the expression of HGTD-P and cleaved caspase 3, as well as real-time PCR detects microRNA expression. MicroRNA agomir is used to inhibit the expression of HGTD-P, and DAPI, TUNEL, and TTC staining are employed to detect cell apoptosis and brain damage. Moreover, in vitro processing assay is used to examine the mechanism by which HI down-regulates miR-139-5p expression. We found that miR-139-5p is down-regulated in neurons and rat brains after HI treatment. The expression pattern of miR-139-5p correlates inversely with that of HGTD-P. Furthermore, miR-139-5p agomir inhibits neuronal apoptosis and attenuates HIBD, which is concurrent with down-regulation of HGTD-P. Moreover, pre-miR-139 processing activity decreases in extracts from OGD neurons, and OGD neuronal extracts attenuates the processing of pre-miR-139 by Dicer. In conclusion, HI induces inhibitors which block the processing step of pre-miR-139, resulting in the down-regulation of mature miR-139-5p. The down-regulation of miR-139-5p plays a critical role in the up-regulation of HGTD-P expression. MiR-139-5p agomir attenuates brain damage when used 12h after HI, providing a longer therapeutic window than anti-apoptosis compounds currently available.

Inhaled NO prevents hyperoxia-induced white matter damage in neonatal rats

White matter damage (WMD) and bronchopulmonary dysplasia (BPD) are the two main complications occurring in very preterm infants. Inhaled nitric oxide (iNO) has been proposed to promote alveolarization in the developing lung, and we have reported that iNO promotes myelination and induces neuroprotection in neonatal rats with excitotoxic brain damage. Our hypothesis is that, in addition to its pulmonary effects, iNO may be neuroprotective in rat pups exposed to hyperoxia. To test this hypothesis, we exposed rat pups to hyperoxia, and we assessed the impact of iNO on WMD and BPD. Rat pups were exposed to either hyperoxia (80% FiO2) or to normoxia for 8 days. Both groups received iNO (5 ppm) or air. We assessed the neurological and pulmonary effects of iNO in hyperoxia-injured rat pups using histological, molecular and behavioral approaches. iNO significantly attenuated the severity of hyperoxia-induced WMD induced in neonatal rats. Specifically, iNO decreased white matter inflammation, cell death, and enhanced the density of proliferating oligodendrocytes and oligodendroglial maturation. Furthermore, iNO triggered an early upregulation of P27kip1 and brain-derived growth factor (BDNF). Whereas hyperoxia disrupted early associative abilities, iNO treatment maintained learning scores to a level similar to that of control pups. In contrast to its marked neuroprotective effects, iNO induced only small and transient improvements of BPD. These findings suggest that iNO exposure at low doses is specifically neuroprotective in an animal model combining injuries of the developing lung and brain that mimicked BPD and WMD in preterm infants.

Ethanol induced acetylation of histone at G9a exon1 and G9a-mediated histone H3 dimethylation leads to neurodegeneration in neonatal mice

The transient exposure of immature rodents to ethanol during postnatal day 7 (P7), comparable to a time point within the third trimester of human pregnancy, induces neurodegeneration. However, the molecular mechanisms underlying the deleterious effects of ethanol on the developing brain are poorly understood. In our previous study, we showed that a high dose administration of ethanol at P7 enhances G9a and leads to caspase-3-mediated degradation of dimethylated H3 on lysine 9 (H3K9me2). In this study, we investigated the potential role of epigenetic changes at G9a exon1, G9a-mediated H3 dimethylation on neurodegeneration and G9a-associated proteins in the P7 brain following exposure to a low dose of ethanol. We found that a low dose of ethanol induces mild neurodegeneration in P7 mice, enhances specific acetylation of H3 on lysine 14 (H3K14ace) at G9a exon1, G9a protein levels, augments the dimethylation of H3K9 and H3 lysine 27 (H3K27me2). However, neither dimethylated H3K9 nor K27 underwent degradation. Pharmacological inhibition of G9a activity prior to ethanol treatment prevented H3 dimethylation and neurodegeneration. Further, our immunoprecipitation data suggest that G9a directly associates with DNA methyltransferase (DNMT3A) and methyl-CpG-binding protein 2 (MeCP2). In addition, DNMT3A and MeCP2 protein levels were enhanced by a low dose of ethanol that was shown to induce mild neurodegeneration. Collectively, these epigenetic alterations lead to association of G9a, DNMT3A and MeCP2 to form a larger repressive complex and have a significant role in low-dose ethanol-induced neurodegeneration in the developing brain.

The neuroprotective role and mechanisms of TERT in neurons with oxygen-glucose deprivation

Telomerase reverse transcriptase (TERT) is reported to protect neurons from apoptosis induced by various stresses including hypoxia-ischemia (HI). However, the mechanisms by which TERT exerts its anti-apoptotic role in neurons with HI injury remain unclear. In this study, we examined the protective role and explored the possible mechanisms of TERT in neurons with HI injury in vitro. Primary cultured neurons were exposed to oxygen and glucose deprivation (OGD) for 3h followed by reperfusion to mimic HI injury in vivo. Plasmids containing TERT antisense, sense nucleotides, or mock were transduced into neurons at 48h before OGD. Expression and distribution of TERT were measured by immunofluorescence labeling and western blot. The expression of cleaved caspase 3 (CC3), Bcl-2 and Bax were detected by western blot. Neuronal apoptosis was measured with terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL). The mitochondrial reactive oxygen species (ROS) were measured by MitoSOX Red staining. Fluorescent probe JC-1 was used to measure the mitochondrial membrane potential (ΔΨm). We found that TERT expression increased at 8h and peaked at 24h in neurons after OGD. CC3 expression and neuronal apoptosis were induced and peaked at 24h after OGD. TERT inhibition significantly increased CC3 expression and neuronal apoptosis after OGD treatment. Additionally, TERT inhibition decreased the expression ratio of Bcl-2/Bax, and enhanced ROS production and ΔΨm dissipation after OGD. These data suggest that TERT plays a neuroprotective role via anti-apoptosis in neurons after OGD. The underlying mechanisms may be associated with regulating Bcl-2/Bax expression ratio, attenuating ROS generation, and increasing mitochondrial membrane potential.