Ruptured erythrocytes inhibit the oxidation of membranes by 15-hydroperoxy-eicosatetraenoic acid

In this study, the pro-oxidant effects of the hydroperoxide, 15-hydroperoxy-eicosatetraenoic acid (15-HPETE), on erythrocyte membranes and the modulation of the oxidation by haem proteins released from ruptured erythrocytes have been assessed. The results indicate that ruptured erythrocytes may act as an antioxidant in protecting membranes against oxidative stress induced by hydroperoxides and that it is the oxyhaemoglobin that is the active constituent of the protective mechanism. An important feature of the mechanism is the peroxidatic action of oxyhaemoglobin and its rate of reaction with 15-HPETE.     

Mitochondrial creatine kinase is a prime target of peroxynitrite-induced modification and inactivation

The reaction of peroxynitrite (PN) with sarcomeric mitochondrial creatine kinase (Mib-CK; EC 2.7.3.2) was observed at different stages of complexity (i) with purified Mi-CK, (ii) with enzyme bound on isolated mitoplasts, and (iii) within intact respiring mitochondria. Creatine-stimulated respiration was abolished by PN concentrations likely to be physiological and far before the respiratory chain itself was affected, thus demonstrating that Mi-CK is a prime target for inactivation by PN in intact mitochondria. The inactivation by PN of Mi-CK was reversed by 22% with 2-mercaptoethanol. More remarkable protective effects were noticed with the full set of CK substrates, e.g. 30 and 50% protection with MgATP plus creatine and MgADP plus phosphocreatine, respectively, but not with each substrate alone. These data indicate an involvement of the active-site Cys-278 residue of Mi-CK in this process. Furthermore, changes in endogenous tryptophan fluorescence intensity and spectral changes after reaction of Mi-CK with PN suggest additional modifications of Trp and Tyr residues. PN-inactivated Mi-CK can no longer be efficiently converted into dimers by incubation with reagents inducing a transition state analog complex at the active site. Thus, obviously, upon reaction of octameric Mi-CK with PN, the octamer-dimer equilibrium of Mi-CK is also affected. The consequences for cellular energy homeostasis and calcium handling are discussed.     

Mercaptoethylguanidine and guanidine inhibitors of nitric-oxide synthase react with peroxynitrite and protect against peroxynitrite-induced oxidative damage

Nitric oxide (NO) produced by the inducible nitric-oxide synthase (iNOS) is responsible for some of the pathophysiological alterations during inflammation. Part of NO-related cytotoxicity is mediated by peroxynitrite, an oxidant species produced from NO and superoxide. Aminoguanidine and mercaptoethylguanidine (MEG) are inhibitors of iNOS and have anti-inflammatory properties. Here we demonstrate that MEG and related compounds are scavengers of peroxynitrite. MEG caused a dose-dependent inhibition of the peroxynitrite-induced oxidation of cytochrome c2+, hydroxylation of benzoate, and nitration of 4-hydroxyphenylacetic acid. MEG reacts with peroxynitrite with a second-order rate constant of 1900 +/- 64 M-1 s-1 at 37 degrees C. In cultured macrophages, MEG reduced the suppression of mitochondrial respiration and DNA single strand breakage in response to peroxynitrite. MEG also reduced the degree of vascular hyporeactivity in rat thoracic aortic rings exposed to peroxynitrite. The free thiol plays an important role in the scavenging effect of MEG. Aminoguanidine neither affected the oxidation of cytochrome c2+ nor reacted with ground state peroxynitrite, but inhibited the peroxynitrite-induced benzoate hydroxylation and 4-hydroxyphenylacetic acid nitration, indicating that it reacts with activated peroxynitrous acid or nitrogen dioxide. Compounds that act both as iNOS inhibitors and peroxynitrite scavengers may be useful anti-inflammatory agents.     

Protection against peroxynitrite-induced fibroblast injury and arthritis development by inhibition of poly(ADP-ribose) synthase

Peroxynitrite, a cytotoxic oxidant formed from nitric oxide (NO) and superoxide, induces DNA strand breakage, which activates the nuclear enzyme poly(ADP-ribose) synthase (PARS; EC 2.4.2.30). The cellular function of PARS was determined in fibroblast lines from PARS knockout animals (PARS-/-) and corresponding wild-type animals (PARS+/+), with the aid of the lipophilic PARS inhibitor 5-iodo-6-amino-1,2-benzopyrone (INH2BP). We investigated the role of PARS in peroxynitrite-induced fibroblast injury in vitro and also in the development of arthritis in vivo. Exposure of embryonic fibroblasts from the PARS+/+ animals to peroxynitrite caused DNA single-stand breakage and PARS activation and caused an acute suppression of mitochondrial respiration. INH2BP protected the PARS+/+ cells against the suppression of mitochondrial respiration in response to peroxynitrite (50-100 microM). Similarly to PARS inhibition with INH2BP, the PARS-/- cells were protected against peroxynitrite-induced injury. The protection against cellular injury by PARS-/- phenotype or INH2BP waned when cells were challenged with higher concentrations of the oxidant. Inhibition of PARS by INH2BP or by PARS-/- phenotype reduced inducible nitric-oxide synthase (iNOS; EC 1.14.13.39) mRNA levels and inhibited production of NO in immunostimulated cells. INH2BP had no peroxynitrite scavenging or hydroxyl radical scavenging effects, and it exerted no additional (nonspecific) effects in the PARS-/- cells. In collagen-induced arthritis, significant staining for nitrotyrosine, a marker of peroxynitrite formation, was found in the inflamed joints. Oral treatment with INH2BP (0.5 g/kg, daily), starting at the onset of arthritis (day 25), delayed the development of the clinical signs at days 26-35 and improved histological status in the knee and paw. Our data demonstrate that deletion of PARS by genetic manipulation or pharmacological inhibition of PARS protects against oxidant-induced cellular injury in vitro and exhibits anti-inflammatory effects in vivo.     

Monoethlenic C20 and C22 fatty acids in marine oil and rapeseed oil. Studies on their oxidation and on their relative ability to inhibit palmitate oxidation in heart and liver mitochondria

1. Carnitine esters of erucic acid (22:1 n-9 cis), cetoleic acid (22:1 n-11 cis), brassidic acid (22:1 n-9 trans), gadoleic acid (20:1 n-9 cis) and oleic acid (18:1 n-9 cis) have been compared as mitochondrial substrates and as inhibitors of palmitoylcarnitine oxidation in heart and liver mitochondria. 2. Both the rate of intramitochondrial-CoA acylation and the rate of beta-oxidation decreases as the chain length increases from C18 to C22. There are no significant differences among the three C22 isomers as oxidizable substrates. 3. All the tested acylcarnitines inhibit palmitoylcarnitine oxidation. The C18 and C20 acylcarnitines inhibit by virtue of being competing substrates; i.e. the respiration is not inhibited. The C22-isomers inhibit also respiration; this shows that the inhibition of palmitolycarnitine oxidation is not compensated for by oxidation of C22-acylcarnitines. Brassidoylcarnitine inhibits the oxidation of palmitoylcarnitine and respiration less than erucoyl-and cetoleoylcarnitine. The different behaviour of the C22-isomers is probably due to the difference in their competitive properties with respect to long-chain acyl-CoA dehydrogenase. 4. All C22 acylcarnitines seem to be relatively better oxidized in the liver than in the heart mitochondria while their inhibitory effect on the usage of the radioactive palmitoylcarnitine is very similar. 5. Palmitoylcarnitine inhibits almost completely the "endogenous" formation of acetyl-CoA presumably from malate via pyruvate in the liver mitochondria while the C22-acylcarnitines cause only a partial inhibiton of this acetyl-CaO formation.     

Human milk glycoconjugates that inhibit pathogens

Breast-fed infants have lower incidence of diarrhea, respiratory disease, and otitis media. The protection by human milk has long been attributed to the presence of secretory IgA. However, human milk contains large numbers and amounts of complex carbohydrates, including glycoproteins, glycolipids, glycosaminoglycans, mucins, and especially oligosaccharides. The oligosaccharides comprise the third most abundant solid constituent of human milk, and contain a myriad of structures. Complex carbohydrate moieties of glycoconjugates and oligosaccharides are synthesized by the many glycosyltransferases in the mammary gland; those with homology to cell surface glycoconjugate pathogen receptors may inhibit pathogen binding, thereby protecting the nursing infant. Several examples are reviewed: A fucosyloligosaccharide inhibits the diarrheagenic effect of stable toxin of Escherichia coli. A different fucosyloligosaccharide inhibits infection by Campylobacter jejuni. Binding of Streptococcus pneumoniae and of enteropathogenic E. coli to their respective receptors is inhibited by human milk oligosaccharides. The 46-kD glycoprotein, lactadherin, inhibits rotavirus binding and infectivity. Low levels of lactadherin in human milk are associated with a higher incidence of symptomatic rotavirus in breast-fed infants. A mannosylated glycopeptide inhibits binding by enterohemorrhagic E. coli. A glycosaminoglycan inhibits binding of gp120 to CD4, the first step in HIV infection. Human milk mucin inhibits binding by S-fimbriated E. coli. The ganglioside, GM1, reduces diarrhea production by cholera toxin and labile toxin of E. coli. The neutral glycosphingolipid, Gb3, binds to Shigatoxin. Thus, many complex carbohydrates of human milk may be novel antipathogenic agents, and the milk glycoconjugates and oligosaccharides may be a major source of protection for breastfeeding infants.     

Mole-rat harderian gland secretions inhibit aggression

The harderian gland secretions of mole-rats, Spalax ehrenbergiusually released by self-grooming, include odorous substances which are sex dependent. Male secretions were the most attractive to both sexes, while female secretions were attractive to males but not to other females. The rate of attacks by females towards intact males was higher than towards males whose harderian gland had been removed. However, grooming by intact male mole-rats decreased the rate of attacks by their opponents, while grooming by males without harderian glands did not; thus the male harderian secretions appear to have appeasement qualities. Grooming by females with and without harderian glands failed to reduce aggression. Unlike intact males, those without harderian glands had almost no volatiles on their fur, and thus are probably not considered to be a threat to conspecifics. Gas chromatography spectra showed that substances of harderian origin were added to the fur during grooming. Some of these substances remained on the fur long after the animal ceased grooming, and appear to give the animal its specific odour, but some volatile substances peaked briefly after grooming, and were probably responsible for the decline of aggression that occurred after grooming. Although grooming has long been considered to be a displacement activity, we suggest that in the mole-rat its performance is too risky to be merely this, and it has acquired the meaning of appeasement through the release of chemical cues.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour     

CD50 monoclonal antibodies inhibit neutrophil activation

The constitutive high expression of CD50 (ICAM-3) on resting leukocytes, coupled with the observation that CD50 is the primary LFA-1 ligand on resting T cells, suggests that CD50 may be an important LFA-1 ligand in the initiation of the immune/inflammatory response. CD50 mAbs have been reported to increase homotypic adhesion of lymphocytes, and lymphocyte adhesion to HUVEC and extracellular matrix proteins. In this study, the effects of CD50 mAbs on neutrophil activation were examined. CD50 mAbs were found to inhibit neutrophil adhesion induced by FMLP and 12-O-tetradecanoyl-phorbol-13-acetate to resting and TNF-activated HUVEC. CD50 mAbs also inhibited neutrophil adhesion stimulated by CD66a, CD66b, CD66c, and CD66d mAbs to HUVEC. CD50 mAbs inhibited the up-regulation of CD11b/CD18 to the neutrophil surface, and the down-regulation of surface CD62L expression. The potential contribution of src family kinases to the previously described tyrosine kinase activity associated with CD50 in neutrophils was also examined. hck and lyn were found to account for much of the tyrosine kinase activity associated with CD50 in neutrophils. The data indicate that CD50 in neutrophils functions not only as a potential ligand for LFA-1, but also regulates the surface expression and activity of CD11b/CD18 and CD62L. In contrast to the effects in lymphocytes, CD50 appears to function as a negative regulator of neutrophil activation.     

Serpins inhibit the toxicity of amyloid peptides

The amyloid plaque in Alzheimer's disease (AD) contains numerous proteins, some of which may be relevant to the pathogenesis of the disease. The serine protease inhibitor alpha1-antichymotrypsin is specifically localized in AD plaques. It is shown here that alpha1-antichymotrypsin and several other serine protease inhibitors (serpins) inhibit the toxicity of amyloid peptides on primary cortical nerve cell cultures as well as a clonal cell line. This inhibition of toxicity is not mediated via the serpin enzyme complex receptor, the transferrin receptor, or by interference with the polymerization of amyloid fibrils. Since a variety of synthetic serine protease inhibitors mimic the effects of serpins on amyloid toxicity, it is likely that the antiprotease activities of serpins are responsible for their biological effects.     

Lipoproteins inhibit macrophage activation by lipoteichoic acid

Regulation of lipid metabolism during infection is thought to be part of host defense, as lipoproteins neutralize endotoxin (LPS) and viruses. Gram-positive infections also induce disturbances in lipid metabolism. Therefore, we investigated whether lipoproteins could inhibit the toxic effects of lipoteichoic acid (LTA), a fragment of gram-positive bacteria. LTA activated RAW264.7 macrophage cells, stimulating production of tumor necrosis factor (TNF) in a dose-dependent matter, but produced less TNF than that seen after LPS activation. High density (HDL) or low density lipoprotein (LDL) alone inhibited the ability of LPS to stimulate TNF production, but had little effect on the activation by LTA. When a maximally effective dose of LTA was mixed with lipoproteins and 10% lipoprotein-depleted plasma (LPDP), the ability of LTA to stimulate macrophage production of TNF was inhibited. HDL, LDL, and the synthetic particle, Soyacal, when mixed with LPDP, were able to inhibit the ability of LTA to activate macrophages. Lipopolysaccharide-binding protein (LBP) substituted for LPDP in catalyzing lipoprotein neutralization of LTA by HDL. Antibody to LBP inhibited the ability of LPDP to induce LTA neutralization by HDL.Thus, lipoproteins can prevent macrophage activation by fragments from both gram-positive and gram-negative microorganisms.-Grunfeld, C., M. Marshall, J. K. Shigenaga, A. H. Moser, P. Tobias, and K. R. Feingold. Lipoproteins inhibit macrophage activation by lipoteichoic acid.     

Sulfonylureas inhibit cytokine-induced eosinophil survival and activation

Eosinophils play a key role in the pathogenesis of asthma and other allergic inflammatory diseases. We have previously shown that treatment of eosinophils with lidocaine preferentially inhibits IL-5-induced survival. This inhibition cannot be overcome by increasing concentrations of IL-5 and is not due to the blocking of Na+ channels by lidocaine. Here we report that one class of K+ channel blockers, the sulfonylureas, inhibits eosinophil survival in a manner similar to lidocaine. The sulfonylurea glyburide inhibits eosinophil survival even at high concentrations of IL-5. In contrast, increasing concentrations of IL-3 or granulocyte-macrophage CSF overcome glyburide inhibition. Glyburide also blocks cytokine-induced eosinophil superoxide production. Similar results were seen with the sulfonylureas tolbutamide and glipizide. Interestingly, the effects of glyburide are not antagonized by the ATP-sensitive K+ channel openers cromakalim, pinacidil, or diazoxide. Although Scatchard analysis of [3H]glyburide binding to eosinophil membranes indicated that the high affinity sulfonylurea receptor (SUR1) is not present on eosinophils, human eosinophils do express mRNA homologous to the sulfonylurea receptor family, in keeping with the presence of a sulfonylurea receptor. Finally, coculture of eosinophils with combinations of glyburide, lidocaine, and dexamethasone resulted in synergistic inhibition of cytokine-mediated eosinophil survival and superoxide production. These results have intriguing clinical implications for the treatment of eosinophil-associated diseases.     

Thiazolidinediones inhibit lipoprotein lipase activity in adipocytes

The thiazolidinediones troglitazone and BRL 49653 improve insulin sensitivity in humans and animals with insulin resistance. Adipose tissue lipoprotein lipase is an insulin-sensitive enzyme. We examined the effects of thiazolidinediones on lipoprotein lipase expression in adipocytes. When added to 3T3-F442A, 3T3-L1, and rat adipocytes in culture, troglitazone and BRL 49653 inhibited lipoprotein lipase activity. This inhibition was observed at concentrations as low as 0.1 microM and within 2 h after addition of the drug. Lipoprotein lipase activity was inhibited in differentiated adipocytes as well as the differentiating cells. Despite this decrease in enzyme activity, these drugs increased mRNA levels in undifferentiated 3T3-F442A and 3T3-L1 cells and had no effect on mRNA expression or synthesis of lipoprotein lipase in differentiated cells. Western blot analysis showed that these drugs did not affect the mass of the enzyme protein. Lipoprotein lipase activity in cultured Chinese hamster ovary cells was not inhibited by troglitazone. Glucose transport, biosynthesis of lipids from glucose or the biosynthesis of proteins were unaffected by thiazolidinediones in differentiated cells, whereas glucose transport and lipid biosynthesis were increased when these drugs were added during differentiation. These results show that troglitazone and BRL 49653 have a specific, post-translational inhibitory effect on lipoprotein lipase in adipocytes, yet they promote lipid accumulation and differentiation in preadipocytes.     

Catheter-based radiotherapy to inhibit restenosis after coronary stenting

BACKGROUND: In animal models of coronary restenosis, intracoronary radiotherapy has been shown to reduce the intimal hyperplasia that is a part of restenosis. We studied the safety and efficacy of catheter-based intracoronary gamma radiation plus stenting to reduce coronary restenosis in patients with previous restenosis. METHODS: Patients with restenosis underwent coronary stenting, as required, and balloon dilation and were then randomly assigned to receive catheter-based irradiation with iridium-192 or placebo. Clinical follow-up was performed, with quantitative coronary angiographic and intravascular ultrasonographic measurements at six months. RESULTS: Fifty-five patients were enrolled; 26 were assigned to the iridium-192 group and 29 to the placebo group. Angiographic studies were performed in 53 patients (96 percent) at a mean (+/-SD) of 6.7+/-2.2 months. The mean minimal luminal diameter at follow-up was larger in the iridium-192 group than in the placebo group (2.43+/-0.78 mm vs. 1.85+/-0.89 mm, P=0.02). Late luminal loss was significantly lower in the iridium-192 group than in the placebo group (0.38+/-1.06 mm vs. 1.03+/-0.97 mm, P=0.03). Angiographically identified restenosis (stenosis of 50 percent or more of the luminal diameter at follow-up) occurred in 17 percent of the patients in the iridium-192 group, as compared with 54 percent of those in the placebo group (P= 0.01). There were no apparent complications of the treatment. CONCLUSIONS: In this preliminary, short-term study of patients with previous coronary restenosis, coronary stenting followed by catheter-based intracoronary radiotherapy substantially reduced the rate of subsequent restenosis.     

Transforming growth factor-betas inhibit mitogen-stimulated proliferation of astrocytes

Aldosterone and thyroid hormone regulation of Na,K-pump biosynthesis has been examined in the distal colon epithelium of rabbits. Qualitative analysis of alpha-subunit isoform distribution (alpha 1, alpha 2, alpha 3) detected only the alpha 1-mRNA in the distal colon epithelium and outer renal medulla, while all three isoforms were observed in rabbit brain. A low-sodium diet led to a rise in serum aldosterone from 0.6 nM to 1.4-1.9 nM and an increase of alpha 1-mRNA to 162%, beta 1-mRNA to 120%, and the number of Na,K-pump units as determined by specific [3H]-ouabain binding to 182% of control by the second day of the diet. While aldosterone levels remained elevated, a spontaneous decrease in serum levels of T3 and T4 to 50-60% of control from the third day of the diet was followed by downregulation of beta 1-mRNA to 55-67%, alpha 1-mRNA to 63-105%, and of [3H]-ouabain binding to 103% of control, suggesting that a reduced rate of synthesis of the beta 1-subunit is rate limiting for Na,K-pump biosynthesis. Substitution with T3 (10 micrograms/kg) at the seventh day with transient restoration of serum T3 to control levels, led to rapid accumulation of beta 1-mRNA to 152%, of alpha 1-mRNA to 135%, and of the number of Na,K-pump units to 153% of control. This is consistent with thyroid hormone having a permissive role for the aldosterone stimulation of Na,K-pump biosynthesis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antioxidants inhibit ATP-sensitive potassium channels in cerebral arterioles

BACKGROUND AND PURPOSE: Hydrogen peroxide and peroxynitrite are capable of generating hydroxyl radical and are commonly suspected as sources of this radical in tissues. It would be useful to distinguish the source of hydroxyl radical in pathophysiological conditions and to clarify the mechanisms by which antioxidants modify vascular actions of oxidants. METHODS: We investigated the effect of three antioxidants--dimethylsulfoxide (DMSO), salicylate, and L-cysteine--on the cerebral arteriolar dilation caused by topical application of hydrogen peroxide and peroxynitrite in anesthetized cats equipped with cranial windows. We also tested the effect of these antioxidants on the vasodilation caused by pinacidil and cromakalim, two known openers of ATP-sensitive potassium channels. RESULTS: DMSO was more effective in inhibiting dilation from hydrogen peroxide, whereas salicylate and L-cysteine were more effective in inhibiting dilation from peroxynitrite. All three antioxidants inhibited dilation in concentrations that were remarkably low (< 1 mmol/L). All three antioxidants inhibited vasodilation from two known potassium channel openers, pinacidil and cromakalim. Their effect was specific because they did not affect dilation from adenosine or nitroprusside. CONCLUSIONS: The findings show that antioxidants block ATP-sensitive potassium channels in cerebral arterioles. This appears to be the mechanism by which antioxidants inhibit the dilation from hydrogen peroxide and peroxynitrite and not through scavenging of a common intermediate, ie, hydroxyl radical. The differences between effectiveness in inhibiting dilation from hydrogen peroxide and peroxynitrite by various antioxidants suggest that hydrogen peroxide and peroxynitrite act at two different sites, one in a water-soluble environment and the other in a lipid-soluble environment.     

Rb functions to inhibit apoptosis during myocyte differentiation

OBJECTIVE: To assess the treatment of continuous data in a sample of obstetric and gynecologic literature. METHODS: We reviewed articles in Obstetrics and Gynecology published in the first 4 months of 1985 and 1995. Data were tabulated on a data form created specifically for this purpose and reviewed for accuracy. RESULTS: The sample set included 170 variables in 102 original articles from Obstetrics and Gynecology published from January to April 1995, inclusive (group A, contemporary articles), and 117 variables in 89 articles published between January and April 1985, inclusive (group B, historic articles). Fifty-three variables (31% of total variables) in group A and 27 variables (23% of total variables) in group B (chi 2, P = .05) were continuous predictor variables. The historic-period articles (63%) were significantly more likely to represent continuous data only as categoric variables than were articles in the contemporary period (38%) (Fisher exact test, P = .037). Correlation coefficients, r values, were provided where possible in ten articles in the contemporary period (83%) and four articles in the historic period (31%) (Fisher exact test, P = .008). In articles in which continuous predictors were treated only as categoric variables, an emphasis was placed on the findings based only on categories in four of 12 (33%) of these articles in 1995 and nine of 13 (69%) in 1985 (Fisher exact test, P = .05). CONCLUSIONS: The treatment of continuous data has improved over the time period reviewed. However, clinicians should be aware that continuous data may be mischaracterized as categoric variables in some journal articles. We hope that in the future, editors will consider requesting r values for all continuous data relations. The quality-of-care implications of using discrete cutoffs of continuous data for patient care should be investigated.     

Human interleukin-10 can directly inhibit T-cell growth

Human interleukin-10 (IL-10) inhibits T-cell proliferation and cytokine production in the presence of monocytes. In this study, we have investigated whether IL-10 can directly inhibit T cells. Highly purified peripheral blood T cells containing less than 0.1% CD14+ cells and unresponsive to phytohemagglutinin (PHA), were growth-inhibited by IL-10 when stimulated with immobilized OKT3 monoclonal antibody (MoAb; 55.4% inhibition). This effect was neutralized by the murine MoAb 19F1 directed against human IL-10. In addition, IL-10 inhibited by 52.5% the proliferation of a human tetanus toxoid-specific T-cell clone (TM11) induced by immobilized OKT3 MoAb in the absence of antigen-presenting function. T-cell growth inhibition by IL-10 did not reflect a cytokine-induced change in the kinetics of T-cell response to immobilized OKT3 MoAb, and was observed over a wide range of cell and OKT3 MoAb concentrations. Addition of 1% to 5% monocytes to highly purified peripheral blood T cells resulted in the emergence of proliferation to PHA and to soluble OKT3 MoAb, but did not significantly affect levels of growth inhibition by IL-10 in the presence of immobilized OKT3 MoAb. Similarly, addition of 10% monocytes to the TM11 T-cell clone resulted in the emergence of proliferation in response to tetanus toxoid, but did not significantly influence growth inhibition by IL-10 in the presence of immobilized OKT3 MoAb. When stimulated with immobilized OKT3 MoAb in the absence of accessory cells, T cells secreted IL-2. Secretion of IL-2 under these conditions was inhibited by IL-10 (51.5% inhibition). Thus, IL-10 can directly inhibit growth and IL-2 production in T cells triggered by immobilized OKT3 MoAb in the absence of monocytes.     

Muscarinic acetylcholine receptor antagonists inhibit chick scleral chondrocytes

PURPOSE: Muscarinic acetylcholine receptors (mAChRs) have been implicated in the control of myopia in humans and in animal models. This study was conducted to determine whether mAChRs influence the growth of the chick sclera and, if so, which mAChR subtypes are involved. METHODS: Sclera and scleral chondrocytes from normal and form-deprived eyes of 10- to 14-day-old chicks were treated with a total of seven ligands: two agonists, carbachol (nonselective) and McN-A-343 (selective for the M1 mAChR subtype); and five antagonists, atropine (nonselective), pirenzepine and telenzepine (M1), gallamine (M2), and 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP; M1 and M3). Incorporation of sulfate into glycosaminoglycans and of thymidine into DNA were quantified and normalized to sample DNA content. Possible toxicity of ligands at high doses was examined by analysis of cell number (by cell counting), viability (by trypan blue exclusion), and cellular metabolic activity (by dehydrogenase activity). RESULTS: Cellular proliferation and extracellular matrix production were inhibited by atropine in whole sclera and in its cartilaginous layer. Sulfate incorporation by chondrocytes from normal and form-deprived eyes was inhibited by mAChR antagonists with a rank order of potency (atropine > pirenzepine = 4-DAMP > gallamine) consistent with regulation by M1, rather than M3 or M2 mAChR subtypes. Pirenzepine inhibited sulfate incorporation by chondrocytes from form-deprived eyes more effectively than those from normal eyes. Chondrocyte cultures were not viable when grown in high doses of any of the ligands used except gallamine. CONCLUSIONS: In chick scleral chondrocytes, synthesis of DNA and glycosaminoglycans was inhibited by mAChR antagonists. This inhibition was probably mediated by the M1 subtype mAChR. Therefore in vivo the sclera may be a site of action for the mAChR antagonists previously used to influence myopia. Although at high concentrations mAChR antagonists tested seemed to be toxic to chondrocytes, at lower doses inhibition occurred without toxic effects.     

Metronidazole may inhibit intestinal colonization with Clostridium difficile

OBJECTIVE: To evaluate the clinical and microbiological efficacy of minocycline in a subgingival local delivery system as an adjunct to tooth scaling and root planing in dogs with periodontal disease. ANIMALS: Nine 4- to 7-year-old Beagles with periodontitis. PROCEDURE: After scaling of teeth and root planing, 2 treatment and 1 or 2 control sites were selected for each dog: treated sites (n = 18) received minocycline hydrochloride periodontal formulation and control sites (n = 12) received ointment base (no minocycline). Gingival crevicular fluid was collected at a baseline (prior to treatment) and at week 4. Clinical and microbiological effects were evaluated and compared among sites. RESULTS: In minocycline-treated sites, clinical indices were significantly decreased at week 4, compared with those at baseline. Minocycline-treated sites were associated with a significant decrease in gingival crevicular fluid, probing depth, and bleeding on probing values, compared with those for control sites at week 4. Compared with that for control sites, total bacteria count in periodontal pockets of minocycline-treated sites had an obvious tendency to decrease by week 4. Proportions of Porphyromonas and Fusobacterium spp were significantly decreased at week 4, compared with proportions at control sites and with pretreatment (baseline) values. CONCLUSIONS: When used as an adjunct to tooth scaling and root planing, minocycline periodontal formulation stimulated favorable clinical and antimicrobial responses.