Cardiac Nerve Growth Factor Overexpression Induces Bone Marrow–derived Progenitor Cells Mobilization and Homing to the Infarcted Heart

Reparative response by bone marrow (BM)-derived progenitor cells (PCs) to ischemia is a multistep process that comprises the detachment from the BM endosteal niche through activation of osteoclasts and proteolytic enzymes (such as matrix metalloproteinases (MMPs)), mobilization to the circulation, and homing to the injured tissue. We previously showed that intramyocardial nerve growth factor gene transfer (NGF-GT) promotes cardiac repair following myocardial infarction (MI) in mice. Here, we investigate the impact of cardiac NGF-GT on postinfarction BM-derived PCs mobilization and homing at different time points after adenovirus-mediated NGF-GT in mice. Immunohistochemistry and flow cytometry newly illustrate the temporal profile of osteoclast and activation of MMP9, PCs expansion in the BM, and liberation/homing to the injured myocardium. NGF-GT amplified these responses and increased the BM levels of active osteoclasts and MMP9, which were not observed in MMP9-deficient mice. Taken together, our results suggest a novel role for NGF in BM-derived PCs mobilization/homing following MI.     

Greater Ciprofloxacin Tolerance as a Possible Selectable Phenotype Underlying the Pandemic Spread of the H30 Subclone of Escherichia coli Sequence Type 131

Minimum bactericidal concentrations (MBCs) for ciprofloxacin were significantly higher among 41 members of the H30 subclone within Escherichia coli sequence type 131 than among 48 other fluoroquinolone-resistant E. coli isolates. This MBC difference, which was not explained by ciprofloxacin MICs, gyrA, parC, and parE mutations, the presence of aac(6′)-Ib-cr, or organic solvent tolerance (a surrogate for efflux pump activity), conceivably could have promoted the pandemic emergence of the H30 sequence type 131 subclone.     

Contribution of functional KIR3DL1 to ankylosing spondylitis

Increasing evidence points to a role for killer immunoglobulin-like receptors (KIRs) in the development of autoimmune diseases. In particular, a positive association of KIR3DS1 (activating receptor) and a negative association of KIR3DL1 (inhibitory receptor) alleles with ankylosing spondylitis (AS) have been reported by several groups. However, none of the studies analyzed these associations in the context of functionality of polymorphic KIR3DL1. To better understand how the KIR3DL1/3DS1 genes determine susceptibility to AS, we analyzed the frequencies of alleles and genotypes encoding functional (KIR3DL1*F) and non-functional (KIR3DL1*004) receptors. We genotyped 83 AS patients and 107 human leukocyte antigen (HLA)-B27-positive healthy controls from the Russian Caucasian population using a two-stage sequence-specific primer PCR, which distinguishes KIR3DS1, KIR3DL1*F and KIR3DL1*004 alleles. For the patients carrying two functional KIR3DL1 alleles, those alleles were additionally genotyped to identify KIR3DL1*005 and KIR3DL1*007 alleles, which are functional but are expressed at low levels. KIR3DL1 was negatively associated with AS at the expense of KIR3DL1*F but not of KIR3DL1*004. This finding indicates that the inhibitory KIR3DL1 receptor protects against the development of AS and is not simply a passive counterpart of the segregating KIR3DS1 allele encoding the activating receptor. However, analysis of genotype frequencies indicates that the presence of KIR3DS1 is a more important factor for AS susceptibility than the absence of KIR3DL1*F. The activation of either natural killer (NK) or T cells via the KIR3DS1 receptor can be one of the critical events in AS development, while the presence of the functional KIR3DL1 receptor has a protective effect. Nevertheless, even individuals with a genotype that carried two inhibitory KIR3DL1 alleles expressed at high levels could develop AS.     

High frequency of hotspot mutations in core genes of Escherichia coli due to short-term positive selection

Core genes comprising the ubiquitous backbone of bacterial genomes are not subject to frequent horizontal transfer and generally are not thought to contribute to the adaptive evolution of bacterial pathogens. We determined, however, that at least one-third and possibly more than one-half of the core genes in Escherichia coli genomes are targeted by repeated replacement substitutions in the same amino acid positions—hotspot mutations. Occurrence of hotspot mutations is driven by positive selection, as their rate is significantly higher than expected by random chance alone, and neither intragenic recombination nor increased mutability can explain the observed patterns. Also, commensal E. coli strains have a significantly lower frequency of mutated genes and mutations per genome than pathogenic strains. E. coli strains causing extra-intestinal infections accumulate hotspot mutations at the highest rate, whereas the highest total number of mutated genes has been found among Shigella isolates, suggesting the pathoadaptive nature of such mutations. The vast majority of hotspot mutations are of recent evolutionary origin, implying short-term positive selection, where adaptive mutations emerge repeatedly but are not sustained in natural circulation for long. Such pattern of dynamics is consistent with source-sink model of virulence evolution.     

Vascular endothelial growth factor (VEGF) affects processing of amyloid precursor protein and β-amyloidogenesis in brain slice cultures derived from transgenic Tg2576 mouse brain

The up-regulation of the angiogenic vascular endothelial growth factor (VEGF) in brains of Alzheimer patients in close relationship to β-amyloid (Aβ) plaques, suggests a link of VEGF action and processing of the amyloid precursor protein (APP). To reveal whether VEGF may affect APP processing, brain slices derived from 17-month-old transgenic Tg2576 mice were exposed with 1 ng/ml VEGF for 6, 24, and 72 h, followed by assessing cytosolic and membrane-bound APP expression, level of both soluble and fibrillar Aβ-peptides, as well as activities of α- and β-secretases in brain slice tissue preparations.Treatment of brain slices with VEGF did not significantly affect the expression level of APP, regardless of the exposure time studied. In contrast, VEGF exposure of brain slices for 6 h reduced the formation of soluble, SDS extractable Aβ(1–40) and Aβ(1–42) as compared to brain slice cultures incubated in the absence of any drug, while the fibrillar Aβ peptides did not change significantly. This effect was less pronounced 24 h after VEGF exposure, but was no longer detectable when brain slices were exposed by VEGF for 72 h, which indicates an adaptive response to chronic VEGF exposure. The VEGF-mediated reduction in Aβ formation was accompanied by a transient decrease in β-secretase activity peaking 6 h after VEGF exposure. To reveal whether the VEGF-induced changes in soluble Aβ-level may be due to actions of VEGF on Aβ fibrillogenesis, the fibrillar status of Aβ was examined using the thioflavin-T binding assay. Incubation of Aβ preparations obtained from Tg2576 mouse brain cortex, in the presence of VEGF slightly decreased the fibrillar content with increasing incubation time up to 72 h. The data demonstrate that VEGF may affect APP processing, at least in vitro, suggesting a role of VEGF in the pathogenesis of Alzheimer's disease.     

Secondary syringe exchange as a model for HIV prevention programs in the Russian Federation

Effective prevention of syringe-borne transmission of HIV and the hepatitis viruses can be undermined if contact between injection drug users and the staff of prevention programs is impeded by police harassment, limited program resources, and the absence of an open "drug scene." All these are commonplace in the Russian Federation. In response, "Project Renewal," the harm reduction program of the AIDS Prevention and Control Center of the Tatarstan Ministry of Health in Kazan, has created a hybrid syringe exchange program that as its primary focus recruited and trained volunteers to provide secondary syringe exchange. To compensate for operational barriers, the program staff identified private venues and trained responsible individuals to work through their own and related networks of injectors to provide clean syringes, other harm reduction supplies, and educational materials, while facilitating the collection and removal of used and potentially contaminated syringes. Program staff developed a detailed set of tracking instruments to monitor, on a daily and weekly basis, the locations and types of contacts and the dissemination of trainings and materials to ensure that the secondary distribution network reaches its target audience. Data show that these secondary exchange sites have proven more productive than the primary mobile and fixed-site syringe exchanges in Kazan. Beginning in 2001, Project Renewal has trained other harm reduction programs in the Russian Federation to use this model of reaching injectors, identifying and training volunteers, and monitoring results of secondary syringe exchange.