Novel anti-bacterial activities of β-defensin 1 in human platelets: suppression of pathogen growth and signaling of neutrophil extracellular trap formation

Human β-defensins (hBD) are antimicrobial peptides that curb microbial activity. Although hBD's are primarily expressed by epithelial cells, we show that human platelets express hBD-1 that has both predicted and novel antibacterial activities. We observed that activated platelets surround Staphylococcus aureus (S. aureus), forcing the pathogens into clusters that have a reduced growth rate compared to S. aureus alone. Given the microbicidal activity of β-defensins, we determined whether hBD family members were present in platelets and found mRNA and protein for hBD-1. We also established that hBD-1 protein resided in extragranular cytoplasmic compartments of platelets. Consistent with this localization pattern, agonists that elicit granular secretion by platelets did not readily induce hBD-1 release. Nevertheless, platelets released hBD-1 when they were stimulated by α-toxin, a S. aureus product that permeabilizes target cells. Platelet-derived hBD-1 significantly impaired the growth of clinical strains of S. aureus. hBD-1 also induced robust neutrophil extracellular trap (NET) formation by target polymorphonuclear leukocytes (PMNs), which is a novel antimicrobial function of β-defensins that was not previously identified. Taken together, these data demonstrate that hBD-1 is a previously-unrecognized component of platelets that displays classic antimicrobial activity and, in addition, signals PMNs to extrude DNA lattices that capture and kill bacteria.     

The roles of cilia in developmental disorders and disease

Cilia are highly conserved organelles that have diverse motility and sensory functions. Recent discoveries have revealed that cilia also have crucial roles in cell signaling pathways and in maintaining cellular homeostasis. As such, defects in cilia formation or function have profound effects on the development of body pattern and the physiology of multiple organ systems. By categorizing syndromes that are due to cilia dysfunction in humans and from studies in vertebrate model organisms, molecular pathways that intersect with cilia formation and function have come to light. Here, we summarize an emerging view that in order to understand some complex developmental pathways and disease etiologies, one must consider the molecular functions performed by cilia.     

Localization of CYP4B1 in the rat nasal cavity and analysis of CYPs as secreted proteins

CYP4B1 is highly expressed in rat nasal respiratory mucosa, and to a lesser extent in olfactory mucosa. Examination of high-power photomicrographs suggests that CYP4B1 may be a secreted protein, based on the fact that immunoreactivity appears to be present in the lumens of ducts of Bowman's glands (rather than intracellular localization, as we observed with an antibody recognizing CYP2F4) and in secretory granules in respiratory mucosa. Furthermore, anti-CYP4B1 immunoreactivity is present on the surface of both respiratory and olfactory mucosa. We used SignalP 3.0 analysis to ascertain the likelihood that rat CYP4B1 is a secreted protein. While this analysis does not suggest that rat CYP4B1 is a secreted protein, several other cytochrome P450 enzymes were predicted to be secreted proteins. The observation that multiple human cytochrome P450s appear to be secreted proteins helps to explain the appearance of anti-cytochrome P450 antigens in cases of human autoimmune liver diseases.     

Mutation of the sensor kinase chvG in Rhizobium leguminosarum negatively impacts cellular metabolism, outer membrane stability, and symbiosis

Two-component signal transduction systems (TCS) are a main strategy used by bacteria to sense and adapt to changes in their environment. In the legume symbiont Rhizobium leguminosarum biovar viciae VF39, mutation of chvG, a histidine kinase, caused a number of pleiotropic phenotypes. ChvG mutants are unable to grow on proline, glutamate, histidine, or arginine as the sole carbon source. The chvG mutant secreted smaller amounts of acidic and neutral surface polysaccharides and accumulated abnormally large amounts of poly-ß-hydroxybutyrate. Mutation of chvG caused symbiotic defects on peas, lentils, and vetch; nodules formed by the chvG mutant were small and white and contained only a few cells that had failed to differentiate into bacteroids. Mutation of chvG also destabilized the outer membrane of R. leguminosarum, resulting in increased sensitivity to membrane stressors. Constitutive expression of ropB, the outer membrane protein-encoding gene, restored membrane stability and rescued the sensitivity phenotypes described above. Similar phenotypes have been described for mutations in other ChvG-regulated genes encoding a conserved operon of unknown function and in the fabXL genes required for synthesis of the lipid A very-long-chain fatty acid, suggesting that ChvG is a key component of the envelope stress response in Rhizobium leguminosarum. Collectively, the results of this study demonstrate the important and unique role the ChvG/ChvI TCS plays in the physiology, metabolism, and symbiotic competency of R. leguminosarum.     

Effects of blood meal source on the reproduction of Culex pipiens quinquefasciatus (Diptera: Culicidae)

Culex pipiens quinquefasciatus were fed blood meals from a live chicken (LC), chicken blood in Alsever's (AC) solution, defibrinated bovine blood (DB), or bovine blood in citrate (CB) and incubated at 28° C. The effects of different blood meal sources were evaluated with respect to rates of blood feeding and reproduction (i.e., fecundity and fertility) over two gonotrophic cycles. Mosquitoes that fed on the first blood meal were subjected to a second blood meal as follows (first blood meal / second blood meal): LC/LC, LC/DB, DB/DB, CB/CB, AC/AC. Fecundity and fertility of Cx. p. quinquefasciatus were significantly (P < 0.05) greater in mosquitoes fed LC blood; however, fecundity and fertility in different treatment groups varied by gonotrophic cycle. These results contribute to our understanding of the impact of blood meal source on feeding and reproduction in Cx. p. quinquefasciatus. The potential impacts of blood meal source on virus transmission experiments are discussed.     

Novel therapies for scar reduction and regenerative healing of skin wounds

Fibrotic scars deposited during skin wound healing can cause disfiguration and loss of dermal function. Scar differentiation involves inputs from multiple cell types in a predictable and overlapping sequence of cellular events that includes inflammation, migration/proliferation and extracellular matrix deposition. Research into the molecular mechanisms underpinning these processes in embryonic and adult wounds has contributed to the development of a growing number of novel therapeutic approaches for improving scar appearance. This review discusses some of these emerging strategies for shifting the balance of healing from scarring to regeneration in the context of non-pathological wounds. Particular focus is given to potential therapies based on transforming growth factor (TGF)-beta signaling and recent unexpected findings involving targeting of gap junctional connexins. Lessons learned in promoting scarless healing of cutaneous injuries might provide a basis for regenerative healing in other scenarios, such as spinal cord rupture or myocardial infarction.     

The reaction of 4,4'-bis-dimethylaminodiphenylcarbinol with the sulfhydryl group. A new reagent for sulfhydryl analysis

4,4′-bis-Dimethylaminodiphenylcarbinol (BDC-OH) dissociates in aqueous buffers at pH values below neutrality to form a resonance-stabilized carbonium-immonium ion (BDC⁺) which exhibits an absorbance maximum at 606 nm. In the presence of 4.0 M guanidine hydrochloride, BDC⁺ has an apparent molar absorption coefficient of 70,800 M^?1cm^?1 and an absorbance maximum of 612 nm. Sulfhydryl groups react with the cation to form S-(4,4′-bis-dimethylaminodiphenylmethyl-) derivatives with a concomitant quantitative loss of the 612-nm absorbance. This quantitative interaction has been exploited in the development of a new and convenient technique for the quantitative determination of sulfhydryl groups in proteins. Results of sulfhydryl determinations on simple thiols and five proteins are presented, along with comparison data obtained via other sulfhydryl techniques.