Dual Roles of Extracellular Histone H3 in Host Defense: Its Differential Regions Responsible for Antimicrobial and Cytotoxic Properties and Their Modes of Action

Extracellular histones play a dual role—antimicrobial and cytotoxic—in host defense. In this study, we evaluated the antimicrobial and cytotoxic activities of histone H3 and identified the responsible molecular regions for these properties. Broth microdilution assays indicated that histone H3 exhibits growth inhibitory activity against not only Gram-negative and -positive bacteria but also fungi. Observations under scanning electron microscopy (SEM) revealed that histone H3 induced morphological abnormalities on the cell surface of a wide range of reference pathogens. MTT assays and SEM observations indicated that histone H3 has strong cytotoxic and cell lytic effects on mammalian normal, immortal, and tumor cell lines. Assays using synthetic peptides corresponding to fragments 1–34 (H3DP1), 35–68 (H3DP2), 69–102 (H3DP3), and 103–135 (H3DP4) of histone H3 molecule demonstrated that its antimicrobial activity and cytotoxicity are elicited by the H3DP2 and H3DP3 protein regions, respectively. Enzyme-linked endotoxin binding assays indicated that histones H3 and H3DP1, H3DP2, and H3DP4, but not H3DP3, exhibited high affinities toward lipopolysaccharide and lipoteichoic acid. Our findings are expected to contribute to the development of new histone H3-based peptide antibiotics that are not cytotoxic

Molecular Cloning, Expression Analyses, and Physiological Roles of Cathelicidins in the Bursa of Fabricius of the Japanese Quail, <i>Coturnix japonica</i>

Antimicrobial peptides (AMPs) act directly on pathogens and maintain the anti-inflammatory effects and activation of immunocompetent cells. Therefore, the activation of the immune system in poultry via the elevation of endogenous AMPs has been attempted. In this study, we focused on the host defense mechanisms in the bursa of Fabricius (BF) of Japanese quail, cloned the cDNA of cathelicidin (CATH)-1 to -3, and analyzed their expression sites. In situ hybridization experiments revealed the mRNA expression of the CATHs in the interfollicular epithelium surrounding the lumen of the quail BF, which suggests that each CATH may exert its antimicrobial action directly in the BF. The intravenous injection of bacterial lipoteichoic acid and lipopolysaccharide endotoxins into the quail promoted the mRNA expression of CATH-1 and CATH-3 in the BF. The addition of CATH-1 or CATH-2 at the time of the antigen injection into mice resulted in antiserum with high antibody titers. Ad libitum administration of butyrate, a short-chain fatty acid, in the drinking water induced an increase in CATH-2 mRNA expression in the BF under certain conditions. These results may improve the defense mechanisms of quail by stimulating CATH expression in the BF through their diet

D2 Dopamine receptor subtype mediates the inhibitory effect of dopamine on TRH-induced prolactin release from the bullfrog pituitary

International audienceDopamine receptors in mammals are known to consist of two D1-like receptors (D1 and D5) and three D2-like receptors (D2, D3 and D4). The aim of this study was to determine the dopamine receptor subtype that mediates the inhibitory action of dopamine on the release of prolactin (PRL) from the amphibian pituitary. Distal lobes of the bullfrog (Rana catesbeiana) were perifused and the amount of PRL released in the effluent medium was measured by means of a homologous enzyme-immunoassay. TRH stimulated the release of PRL from perifused pituitaries. Dopamine suppressed TRH-induced elevation of PRL release. Quinpirole (a D2 receptor agonist) also suppressed the stimulatory effect of TRH on the release of PRL, whereas SKF-38393 (a D1 receptor agonist) exhibited no such an effect. The inhibitory action of dopamine on TRH-induced PRL release from the pituitary was nullified by the addition of L-741,626 (a selective D2 receptor antagonist) to the medium, but not by the addition of SCH-23390 (a selective D1 receptor antagonist). These data indicate that the inhibitory effect of dopamine on TRH-evoked PRL release from the bullfrog pituitary gland is mediated through D2 dopamine receptors

Circulating oxidized LDL forms complexes with beta2-glycoprotein I:implication as an atherogenic autoantigen

beta(2)-glycoprotein I (beta(2)-GPI) is a major antigen for antiphospholipid antibodies (Abs, aPL) present in patients with antiphospholipid syndrome (APS). We recently reported (I. Lipid Res., 42: 697, 200 1; J Lipid Res., 43: 1486, 2002) that beta(2)-GPI specifically binds to Cu2+-oxidized LDL (oxLDL) and that the beta(2)-GPI ligands are omega-carboxylated 7-ketocholesteryl esters. In the present study, we demonstrate that oxLDL forms stable and nondissociable complexes with beta(2)-GPI in serum, and that high serum levels of the complexes are associated with arterial thrombosis in APS. A conjugated ketone function at the 7-position of cholesterol as well as the omega-carboxyl function of the beta(2)-GPI ligands was necessary for beta(2)-GPI binding. The ligand-mediated noncovalent interaction of beta(2)-GPI and oxLDL undergoes a temperature- and time-dependent conversion to much more stable but readily dissociable complexes in vitro at neutral pH. In contrast, stable and nondissociable beta(2)-GPI-oxLDL complexes were frequently detected in sera from patients with APS and/or systemic lupus erythematodes. Both the presence Of beta(2)-GPI-oxLDL complexes and IgG Abs recognizing these complexes were strongly associated with arterial thrombosis. Further, these same Abs correlated with IgG immune complexes containing beta(2)-GPI or LDL.jlr Thus, the beta(2)-GPI-oxLDL complexes acting as an autoantigen are closely associated with autoimmune-mediated atherogenesis