IntroductionAcute kidney injury following surgery incurs significant mortality with no proven preventative therapy. We investigated whether the α2 adrenoceptor agonist dexmedetomidine (Dex) provides protection against ischemia-reperfusion induced kidney injury in vitro and in vivo.MethodsIn vitro, a stabilised cell line of human kidney proximal tubular cells (HK2) was exposed to culture medium deprived of oxygen and glucose. Dex decreased HK2 cell death in a dose-dependent manner, an effect attenuated by the α2 adrenoceptor antagonist atipamezole, and likely transduced by phosphatidylinositol 3-kinase (PI3K-Akt) signaling. In vivo C57BL/6J mice received Dex (25 μg/kg, intraperitoneal (i.p.)) 30 minutes before or after either bilateral renal pedicle clamping for 25 minutes or right renal pedicle clamping for 40 minutes and left nephrectomy.ResultsPre- or post-treatment with Dex provided cytoprotection, improved tubular architecture and function following renal ischemia. Consistent with this cytoprotection, dexmedetomidine reduced plasma high-mobility group protein B1 (HMGB-1) elevation when given prior to or after kidney ischemia-reperfusion; pretreatment also decreased toll-like receptor 4 (TLR4) expression in tubular cells. Dex treatment provided long-term functional renoprotection, and even increased survival following nephrectomy.ConclusionsOur data suggest that Dex likely activates cell survival signal pAKT via α2 adrenoceptors to reduce cell death and HMGB1 release and subsequently inhibits TLR4 signaling to provide reno-protection.

Infections with bacterial or fungal biofilms have emerged as a major public heath concern because biofilm-growing cells are highly resistant to both antibiotics and host immune defenses. This review focuses on the progress in understanding the mechanisms of biofilm-specific antimicrobial resistance and in developing innovative therapeutic measures based on novel antibiofilm agents.

BackgroundAphA is the master quorum-sensing (QS) regulator operating at low cell density in vibrios. Molecular regulation of target genes by AphA has been characterized in Vibrio harveyi and V. cholerae, but it is still poorly understood in V. parahaemolyticus.Methodology/Principal FindingsThe AphA proteins are extremely conserved in V. parahaemolyticus, Vibrio sp. Ex25, Vibrio sp. EJY3, V. harveyi, V. vulnificus, V. splendidus, V. anguillarum, V. cholerae, and V. furnissii. The above nine AphA orthologs appear to recognize conserved cis-acting DNA signals which can be represented by two consensus constructs, a 20 bp box sequence and a position frequency matrix. V. parahaemolyticus AphA represses the transcription of ahpA, qrr4, and opaR through direct AphA-target promoter DNA association, while it inhibits the qrr2-3 transcription in an indirect manner. Translation and transcription starts, core promoter elements for sigma factor recognition, Shine-Dalgarno sequences for ribosome recognition, and AphA-binding sites (containing corresponding AphA box-like sequences) were determined for the three direct AphA targets ahpA, qrr4, and opaR in V. parahaemolyticus.Conclusions/SignificanceAphA-mediated repression of ahpA, qrr2-4, and opaR was characterized in V. parahaemolyticus by using multiple biochemical and molecular experiments. The computational promoter analysis indicated the conserved mechanism of transcriptional regulation of QS regulator-encoding genes ahpA, qrr4, and opaR in vibrios.

Biofilm formation in Staphylococcus epidermidis is mediated by icaADBC-dependent and -independent pathways. Subinhibitory concentrations of erythromycin, azithromycin, and clarithromycin enhanced, in a dosedependent manner, the level of biofilm formation by 20% (21/105 isolates) by macrolide-resistant ica-positive and -negative isolates tested in vitro. The presence of ica, however, apparently produced an enhanced effect on biofilm formation. The levels of expression of the biofilm-related genes icaA, atlE, fruA, pyrR, sarA, and sigB were increased in response to erythromycin. The results likely underscore the potential clinical relevance of macrolide-induced biofilm growth.Staphylococcus epidermidis, a key nosocomial pathogen, is frequently associated with the use of indwelling medical devices and forms biofilms (9). The latter is mediated by icaADBC-dependent and -independent pathways (8, 17). The ica operon encodes enzymes that are involved in the production of polysaccharide intercellular adhesion (PIA), which mediates the intercellular adherence of bacteria and the accumulation of multilayer biofilms (8). Nevertheless, ica is not ubiquitously distributed in S. epidermidis (5,8,21), and icanegative isolates also produce biofilm (19). Furthermore, the impact of exogenous substances, such as antibiotics, on bacterial biofilm formation has also drawn much attention (3,6,7,11,12,23), although the numbers of studies performed with S. epidermidis are still limited. Macrolides, which include erythromycin (ERY), clarithromycin (CLR), and azithromycin (AZM), are among the most frequently used antibiotics in clinical settings. A subinhibitory concentration of ERY induced ica expression (20), suggesting a possible role of macrolides in biofilm formation, but the eradication of the slimelike glycocalyx matrix and, thus, the eradication of antibiofilm activity by a subinhibitory concentration of CLR in a CLRresistant isolate of S. epidermidis (whose ica status was unknown) were also reported (24). The study described here was thus carried out to investigate the role of macrolides in biofilm formation and its relation to the ica status of S. epidermidis. We show that a large number of clinical isolates of S. epidermidis had significantly enhanced levels of biofilm formation after treatment with macrolides and that biofilm formation was independent of the ica status.Of 121 S. epidermidis strains isolated from our hospital during the period from August 2007 to December 2008, 105 isolates (87%) were resistant to ERY (MIC Ͼ 8 g/ml), with most of the isolates being highly resistant to ERY, CLR, and AZM (MICs Ն 128 g/ml), although they were susceptible to vancomycin (VAN; MICs ϭ 1 to 2 g/ml). By using a microtiter plate assay for biofilm formation (1) with cells grown in tryptic soy broth medium, ERY at 1/4ϫ MIC (i.e., over the range of 4 to 32 g/ml) was found to significantly enhance the level of biofilm formation in 20% (21/105) of the ERY-resistant isolates (Tables 1 and 2). Two other macrolides, AZM and CLR, also caused a s...