Characterization of inflammatory responses to eccentric exercise in humans

Eccentric exercise commonly results in muscle damage. The primary sequence of events leading to exercise-induced muscle damage is believed to involve initial mechanical disruption of sarcomeres, followed by impaired excitation-contraction coupling and calcium signaling, and finally, activation of calcium-sensitive degradation pathways. Muscle damage is characterized by ultrastructural changes to muscle architecture, increased muscle proteins and enzymes in the bloodstream, loss of muscular strength and range of motion and muscle soreness. The inflammatory response to exercise-induced muscle damage is characterized by leukocyte infiltration and production of pro-inflammatory cytokines within damaged muscle tissue, systemic release of leukocytes and cytokines, in addition to alterations in leukocyte receptor expression and functional activity. Current evidence suggests that inflammatory responses to muscle damage are dependent on the type of eccentric exercise, previous eccentric loading (repeated bouts), age and gender. Circulating neutrophil counts and systemic cytokine responses are greater after eccentric exercise using a large muscle mass (e.g. downhill running, eccentric cycling) than after other types of eccentric exercise involving a smaller muscle mass. After an initial bout of eccentric exercise, circulating leukocyte counts and cell surface receptor expression are attenuated. Leukocyte and cytokine responses to eccentric exercise are impaired in elderly individuals, while cellular infiltration into skeletal muscle is greater in human females than males after eccentric exercise. Whether alterations in intracellular calcium homeostasis influence inflammatory responses to muscle damage is uncertain. Furthermore, the effects of antioxidant supplements are variable, and the limited data available indicates that anti-inflammatory drugs largely have no influence on inflammatory responses to eccentric exercise. In this review, we compare local versus systemic inflammatory responses, and discuss some of the possible mechanisms regulating the inflammatory responses to exercise-induced muscle damage in humans.

Systematic inflammatory responses to maximal versus submaximal lengthening contractions of the elbow flexors

We compared changes in markers of muscle damage and systemic inflammation after submaximal and maximal lengthening muscle contractions of the elbow flexors. Using a cross-over design, 10 healthy young men not involved in resistance training completed a submaximal trial (10 sets of 60 lengthening contractions at 10% maximum isometric strength, 1 min rest between sets), followed by a maximal trial (10 sets of three lengthening contractions at 100% maximum isometric strength, 3 min rest between sets). Lengthening contractions were performed on an isokinetic dynamometer. Opposite arms were used for the submaximal and maximal trials, and the trials were separated by a minimum of two weeks. Blood was sampled before, immediately after, 1 h, 3 h, and 1-4 d after each trial. Total leukocyte and neutrophil numbers, and the serum concentration of soluble tumor necrosis factor-alpha receptor 1 were elevated after both trials (P < 0.01), but there were no differences between the trials. Serum IL-6 concentration was elevated 3 h after the submaximal contractions (P < 0.01). The concentrations of serum tumor necrosis factor-alpha, IL-1 receptor antagonist, IL-10, granulocyte-colony stimulating factor and plasma C-reactive protein remained unchanged following both trials. Maximum isometric strength and range of motion decreased significantly (P < 0.001) after both trials, and were lower from 1-4 days after the maximal contractions compared to the submaximal contractions. Plasma myoglobin concentration and creatine kinase activity, muscle soreness and upper arm circumference all increased after both trials (P < 0.01), but were not significantly different between the trials. Therefore, there were no differences in markers of systemic inflammation, despite evidence of greater muscle damage following maximal versus submaximal lengthening contractions of the elbow flexors.

Downregulation of IgE antibody and allergic responses in the lung by epidermal biolistic microparticle delivery

Background: Biolistic injections provide a needle-free delivery of antigen-laden microparticles to the epithelium. The precision of the injection preferentially targets the Langerhans cell network, which, although ideal for vaccination, might not be suitable for the downregulation of immune responses in immunotherapy. Objective: We sought to determine the ability of biolistic injection of antigen into the epithelium of sensitized mice to inhibit IgE antibody and lung inflammatory responses produced by further exposure to antigen. Methods: Mice were sensitized by means of a needle injection of ovalbumin (OVA) in alum and given a series of biolistic injections of OVA or vehicle control, followed by a boost of OVA in alum. Serum IgE and IgG antibodies were measured before and after the boost. The mice were then challenged intranasally, and the infiltration of inflammatory cells was measured by means of bronchoalveolar lavage. Airway reactivity of the challenged mice was measured by examining responses to methacholine with forced oscillatory techniques. Results: Biolistic injection of OVA into the dorsal skin of sensitized mice markedly inhibited IgE and IgG1 antibody responses induced by boosting. IgG2a antibody responses were reduced rather than stimulated. The eosinophilic inflammation in the bronchoalveolar lavage fluid induced by intranasal challenge was also markedly inhibited. Lung hyperreactivity showed an initial increase and then a decrease of responsiveness to methacholine, with elastance returning to the level of unsensitized mice. Biolistic injection into the buccal epithelium was also inhibitory. Conclusions: Biolistic injection of allergen inhibited the boosting of IgE antibody and eosinophilic lung inflammatory responses without inducing TO immunity.

Small molecular probes for G-protein-coupled C5a receptors: Conformationally constrained antagonists derived from the C terminus of the human plasma protein C5a

Activation of the human complement system of plasma proteins in response to infection or injury produces a 4-helix bundle glycoprotein (74 amino acids) known as C5a. C5a binds to G-protein-coupled receptors on cell surfaces triggering receptor-ligand internalization, signal transduction, and powerful inflammatory responses. Since excessive levels of C5a are associated with autoimmune and chronic inflammatory disorders, inhibitors of receptor activation may have therapeutic potential. We now report solution structures and receptor-binding and antagonist activities for some of the first small molecule antagonists of C5a derived from its hexapeptide C terminus. The antagonist NMe-Phe-Lys-Pro-D-Cha-Trp-D-Arg-CO2H (1) surprisingly shows an unusually well-defined solution structure as determined by H-1 NMR spectroscopy. This is one of the smallest acyclic peptides found to possess a defined solution conformation, which can be explained by the constraining role of intramolecular hydrogen bonding. NOE and coupling constant data, slow deuterium exchange, and a low dependence on temperature for the chemical shift of the D-Cha-NH strongly indicate an inverse gamma turn stabilized by a D-Cha-NH ... OC-Lys hydrogen bond. Smaller conformational populations are associated with a hydrogen bond between Trp-NH ... OC-Lys, defining a type II beta turn distorted by the inverse gamma turn incorporated within it. An excellent correlation between receptor-affinity and antagonist activity is indicated for a limited set of synthetic peptides. Conversion of the C-terminal carboxylate of 1 to an amide decreases antagonist potency 5-fold, but potency is increased up to 10-fold over 1 if the amide bond is made between the C-terminal carboxylate and a Lys/Orn side chain to form a cyclic analogue. The solution structure of cycle 6 also shows gamma and beta turns; however, the latter occurs in a different position, and there are clear conformational changes in 6 vs 1 that result in enhanced activity. These results indicate that potent C5a antagonists can be developed by targeting site 2 alone of the C5a receptor and define a novel pharmacophore for developing powerful receptor probes or drug candidates.

Ancient missense mutations in a new member of the RoRet gene family are likely to cause familial Mediterranean fever

Familial Mediterranean fever (FMF) is a recessively inherited disorder characterized by dramatic episodes of fever and serosal inflammation. This report describes the cloning of the gene likely to cause FMF from a 115-kb candidate interval on chromosome 16p. Three different missense mutations were identified in affected individuals, but not in normals. Haplotype and mutational analyses disclosed ancestral relationships among carrier chromosomes in populations that have been separated for centuries. The novel gene encodes a 3.7-kb transcript that is almost exclusively expressed in granulocytes. The predicted protein, pyrin, is a member of a family of nuclear factors homologous to the Ro52 autoantigen. The cloning of the FMF gene promises to shed light on the regulation of acute inflammatory responses.

Exercise-induced alterations in neutrophil degranulation and respiratory burst activity: possible mechanisms of action

Neutrophils constitute 50-60% of all circulating leukocytes; they present the first line of microbicidal defense and are involved in inflammatory responses. To examine immunocompetence in athletes, numerous studies have investigated the effects of exercise on the number of circulating neutrophils and their response to stimulation by chemotactic stimuli and activating factors. Exercise causes a biphasic increase in the number of neutrophils in the blood, arising from increases in catecholamine and cortisol concentrations. Moderate intensity exercise may enhance neutrophil respiratory burst activity, possibly through increases in the concentrations of growth hormone and the inflammatory cytokine IL-6. In contrast, intense or long duration exercise may suppress neutrophil degranulation and the production of reactive oxidants via elevated circulating concentrations of epinephrine (adrenaline) and cortisol. There is evidence of neutrophil degranulation and activation of the respiratory burst following exercise-induced muscle damage. In principle, improved responsiveness of neutrophils to stimulation following exercise of moderate intensity could mean that individuals participating in moderate exercise may have improved resistance to infection. Conversely, competitive athletes undertaking regular intense exercise may be at greater risk of contracting illness. However there are limited data to support this concept. To elucidate the cellular mechanisms involved in the neutrophil responses to exercise, researchers have examined changes in the expression of cell membrane receptors, the production and release of reactive oxidants and more recently, calcium signaling. The investigation of possible modifications of other signal transduction events following exercise has not been possible because of current methodological limitations. At present, variation in exercise-induced alterations in neutrophil function appears to be due to differences in exercise protocols, training status, sampling points and laboratory assay techniques.

The effects of intra-amniotic injection of periodontopathic lipopolysaccharides in sheep

Objective: Periodontal disease may cause several complications of pregnancy, including fetal death. The purpose of this study was to investigate in sheep the effects of the intra-amniotic injection of lipopolysaccharide from 3 periodontopathic organisms and to compare these effects with those resulting from similar injection of Escherichia coli lipopolysaccharide. The outcomes that were studied included the rates of fetal death and the features of inflammation and lung maturation in survivors. Study design: At 118 days of pregnancy, ewes that were bearing single fetuses were allocated at random to receive intra-amniotic injections of saline solution (n = 13 fetuses), or lipopolysaccharide from Porphyromonas gingivalis (in doses from 0.1 to 10 tug [n = 22 fetuses]), Actinobacillus actinomycetemcomitans (10 mg [n = 6 fetuses]; 1 mg [n = 6 fetuses]), Fusobacterium nucleation (10 mg [n = 6 fetuses]) or Escherichia coli (10 mg [n = 14 fetuses]; 1 mg [n = 7 fetuses]). Surviving fetuses were delivered abdominally at 125 days of gestation (term, 150 days). Results: When compared with Escherichia coli lipopolysaccharide at similar dosages, periodontopathic lipopolysaccharides had high rates of fetal lethality. Only 6 of 22 fetuses that were exposed to intra-amniotic Porphyromonas gingivalis lipopolysaccharide survived doses of 0.1 to 10 mg, and only 3 of 6 fetuses survived 10-mg Actinobacillus actinomycetemcomitans lipopolysaccharide. Escherichia coli lipopolysaccharide did not cause fetal loss when given at doses of 10 mg (n = 14 fetuses) or l mg (n = 7 fetuses). Fetuses that survived exposure to these lipopolysaccharides showed features of inflammation in amniotic fluid and cord blood at birth and enhanced lung maturation. Conclusion: Lipopolysaccharides from these 3 periodontopathic organisms have much higher rates of fetal lethality than Escherichia coli lipopolysaccharide but can cause similar intrauterine inflammatory responses and improvements in lung volumes in survivors. Sources of inflammation that are distant from the uterus may underlie a proportion of unexplained stillbirth and other complications of pregnancy. (c) 2005 Mosby, Inc. All rights reserved.

Defenses against oxidative stress in Neisseria gonorrhoeae: A system tailored for a challenging environment

Neisseria gonorrhoeae is a host-adapted pathogen that colonizes primarily the human genitourinary tract. This bacterium encounters reactive oxygen and reactive nitrogen species as a consequence of localized inflammatory responses in the urethra of males and endocervix of females and also of the activity of commensal lactobacilli in the vaginal flora. This review describes recent advances in the understanding of defense systems against oxidative stress in N. gonorrhoeae and shows that while some of its defenses have similarities to the paradigm established with Escherichia coli, there are also some key differences. These differences include the presence of a defense system against superoxide based on manganese ions and a glutathione-dependent system for defense against nitric oxide which is under the control of a novel MerR-like transcriptional regulator. An understanding of the defenses against oxidative stress in N. gonorrhoeae and their regulation may provide new insights into the ways in which this bacterium survives challenges from polymorphonuclear leukocytes and urogenital epithelial cells.

LPS regulates proinflammatory gene expression in macrophages by altering histone deacetylase expression

Bacterial LPS triggers dramatic changes in gene expression in macrophages. We show here that LPS regulated several members of the histone deacetylase (HDAC) family at the mRNA level in murine bone marrow-derived macrophages (BMM). LPS transiently repressed, then induced a number of HDACs (Hdac-4, 5, 7) in BMM, whereas Hdac-1 mRNA was induced more rapidly. Treatment of BMM with trichostatin A (TSA), an inhibitor of HDACs, enhanced LPS-induced expression of the Cox-2, Cxcl2, and Ifit2 genes. In the case of Cox-2, this effect was also apparent at the promoter level. Overexpression of Hdac-8 in RAW264 murine macrophages blocked the ability of LPS to induce Cox-2 mRNA. Another class of LPS-inducible genes, which included Ccl2, Ccl7, and Edn1, was suppressed by TSA, an effect most likely mediated by PU.1 degradation. Hence, HDACs act as potent and selective negative regulators of proinflammatory gene expression and act to prevent excessive inflammatory responses in macrophages.

Specific modulation of airway epithelial tight junctions by apical application of an occludin peptide

Tight junctions are directly involved in regulating the passage of ions and macromolecules (gate functions) in epithelial and endothelial cells. The modulation of these gate functions to transiently regulate the paracellular permeability of large solutes and ions could increase the delivery of pharmacological agents or gene transfer vectors. To reduce the inflammatory responses caused by tight junction-regulating agents, alternative strategies directly targeting specific tight junction proteins could prove to be less toxic to airway epithelia. The apical delivery of peptides corresponding to the first extracellular loop of occludin to transiently modulate apical paracellular flux has been demonstrated in intestinal epithelia. We hypothesized that apical application of these occludin peptides could similarly modulate tight junction permeability in airway epithelia. Thus, we investigated the effects of apically applied occludin peptide on the paracellular permeability of molecular tracers and viral vectors in well differentiated human airway epithelial cells. The effects of occludin peptide on cellular toxicity, tight junction protein expression and localization, and membrane integrity were also assessed. Our data showed that apically applied occludin peptide significantly reduced transepithelial resistance in airway epithelia and altered tight junction permeability in a concentration-dependent manner. These alterations enhanced the paracellular flux of dextrans as well as gene transfer vectors. The occludin peptide redistributed occludin but did not alter the expression or distribution of ZO-1, claudin-1, or claudin-4. These data suggest that specific targeting of occludin could be a better-suited alternative strategy for tight junction modulation in airway epithelial cells compared with current agents that modulate tight junctions.

The use of hypertonic saline for treating intracranial hypertension after traumatic brain injury

The past decade has witnessed a resurgence of interest in the use of hypertonic saline for low-volume resuscitation after trauma. Preliminary studies suggested that benefits are limited to a subgroup of trauma patients with brain injury, but a recent study of prehospital administration of hypertonic saline to patients with traumatic brain injury failed to confirm a benefit. Animal and human studies have demonstrated that hypertonic saline has clinically desirable physiological effects on cerebral blood flow, intracranial pressure, and inflammatory responses in models of neurotrauma. There are few clinical studies in traumatic brain injury with patient survival as an end point. In this review, we examined the experimental and clinical knowledge of hypertonic saline as an osmotherapeutic agent in neurotrauma.

Plasma steroids and steroid-binding capacity in male semelparous dasyurid marsupials (Phascogale tapoatafa) that survive beyond the breeding season in captivity

The semelparous dasyurids display a unique life history, in that all males die within a few weeks of the completion of the breeding season. Studies of several semelparous species have revealed that the male die-off is stress-related, and accompanied by increased plasma androgen and cortisol levels and decreased corticosteroid binding capacity, resulting in suppression of immune and inflammatory responses. This study examines the endocrine profile of male brush-tailed phascogales (Phascogale tapoatafa) that survive beyond the breeding season in captivity. Plasma cortisol, corticosteroid binding globulin and albumin levels were monitored in both males and females and steroid partitioning calculated. Captive males surviving beyond the breeding season did not show the elevation in plasma cortisol and decrease in corticosteroid binding capacity reported in wild males. Plasma albumin concentrations also remained constant during the sampling period. These data indicate that captive males do not undergo the same stress response described in wild populations. (c) 2006 Elsevier Inc. All rights reserved.