Methemoglobin formation in mutant hemoglobin α chains: electron transfer parameters and rates.

Hemoglobin-mediated transport of dioxygen (O2) critically depends on the stability of the reduced (Fe2+) form of the heme cofactors. Some protein mutations stabilize the oxidized (Fe3+) state (methemoglobin, Hb M), causing methemoglobinemia, and can be lethal above 30%. The majority of the analyses of factors influencing Hb oxidation are retrospective and give insights only for inner-sphere mutations of heme (His58, His87). Herein, we report the first all-atom molecular dynamics simulations on both redox states and calculations of the Marcus electron transfer (ET) parameters for the α chain Hb oxidation and reduction rates for Hb M. The Hb wild-type (WT) and most of the studied α chain variants maintain globin structure except the Hb M Iwate (H87Y). The mutants forming Hb M tend to have lower redox potentials and thus stabilize the oxidized (Fe3+) state (in particular, the Hb Miyagi variant with K61E mutation). Solvent reorganization (λsolv 73-96%) makes major contributions to reorganization free energy, whereas protein reorganization (λprot) accounts for 27-30% except for the Miyagi and J-Buda variants (λprot ∼4%). Analysis of heme-solvent H-bonding interactions among variants provide insights into the role of Lys61 residue in stabilizing the Fe2+ state. Semiclassical Marcus ET theory-based calculations predict experimental kET for the Cyt b5-Hb complex and provide insights into relative reduction rates for Hb M in Hb variants. Thus, our methodology provides a rationale for the effect of mutations on the structure, stability, and Hb oxidation reduction rates and has potential for identification of mutations that result in methemoglobinemia.

Thymosin beta 4 up-regulates miR-200a expression and induces differentiation and survival of rat brain progenitor cells.

Thymosin beta 4 (Tß4), a secreted 43 amino acid peptide, promotes oligodendrogenesis, and improves neurological outcome in rat models of neurologic injury. We demonstrated that exogenous Tß4 treatment up-regulated the expression of the miR-200a in vitro in rat brain progenitor cells and in vivo in the peri-infarct area of rats subjected to middle cerebral artery occlusion (MCAO). The up-regulation of miR-200a down-regulated the expression of the following targets in vitro and in vivo models: (i) growth factor receptor-bound protein 2 (Grb2), an adaptor protein involved in epidermal growth factor receptor (EGFR)/Grb2/Ras/MEK/ERK1/c-Jun signaling pathway, which negatively regulates the expression of myelin basic protein (MBP), a marker of mature oligodendrocyte; (ii) ERRFI-1/Mig-6, an endogenous potent kinase inhibitor of EGFR, which resulted in activation/phosphorylation of EGFR; (iii) friend of GATA 2, and phosphatase and tensin homolog deleted in chromosome 10 (PTEN), which are potent inhibitors of the phosphatidylinositol-3-kinase (PI3K)/AKT signaling pathway, and resulted in marked activation of AKT; and (iv) transcription factor, p53, which induces pro-apoptotic genes, and possibly reduced apoptosis of the progenitor cells subjected to oxygen glucose deprivation (OGD). Anti-miR-200a transfection reversed all the effects of Tß4 treatment in vitro. Thus, Tß4 up-regulated MBP synthesis, and inhibited OGD-induced apoptosis in a novel miR-200a dependent EGFR signaling pathway. Our findings of miR-200a-mediated protection of progenitor cells may provide a new therapeutic importance for the treatment of neurologic injury. Tß4-induced micro-RNA-200a (miR-200a) regulates EGFR signaling pathways for MBP synthesis and apoptosis: up-regulation of miR-200a after Tß4 treatment, increases MBP synthesis after targeting Grb2 and thereby inactivating c-Jun from inhibition of MBP synthesis; and also inhibits OGD-mediated apoptosis after targeting EGFR inhibitor (Mig-6), PI3K inhibitors (FOG2 and Pten) and an inducer (p53) of pro-apoptotic genes, for AKT activation and down-regulation of p53. These findings may contribute the therapeutic benefits for stroke and other neuronal diseases associated with demyelination disorders.

Impact of BioFire® Blood Culture Identification (BCID) panels on antibiotic management of bacteremia due to select organisms.

The purpose of this study was to assess changes in time to optimal therapy (TTOT) for bacteremia due to select organisms after implementation of the BioFire® FilmArray® blood culture identification panels at two community teaching hospitals. TTOT (days) was similar in Pre-BCID compared to BCID1 and BCID2 [(2.48 vs. 2.65, p=0.10); (2.48 vs. 2.37, p=0.27)]. There were no significant differences in time to effective antimicrobial therapy between groups. However, there were significantly more therapy changes and appropriate carbapenem use within 24 hours of the Gram stain result for gram-negative organisms in the BCID2 arm compared to the Pre-BCID arm. Additionally, a significant reduction in the duration of vancomycin for gram-positive organisms was noted in the BCID2 arm compared to the Pre-BCID arm. These findings suggest that the incorporation of the BCID2 panel resulted in changes in prescribing practices, leading to more appropriate antimicrobial utilization in a subset of patients.