Skeletal muscle satellite cell function is largely dictated by the surrounding environment following injury. Immune cell infiltration dominates the extracellular space in the injured area, resulting in increased cytokine concentrations. While increased pro-inflammatory cytokine expression has been previously established in the first 3 days following injury, less is known about the time course of cytokine expression and the specific mechanisms of cytokine induced myoblast function. Therefore, the expression of IL-1β and IL-6 at several time points following injury, and their effects on myoblast proliferation, were examined. In order to do this, skeletal muscle was injured using barium chloride in mice and tissue was collected 1, 5, 10, and 28 days following injury. Mechanisms of cytokine induced proliferation were determined in cell culture using both primary and C2C12 myoblasts. It was found that there is a ∼20-fold increase in IL-1β (p≤0.05) and IL-6 (p = 0.06) expression 5 days following injury. IL-1β increased proliferation of both primary and C2C12 cells ∼25%. IL-1β stimulation also resulted in increased NF-κB activity, likely contributing to the increased proliferation. These data demonstrate for the first time that IL-1β alone can increase the mitogenic activity of primary skeletal muscle satellite cells and offer insight into the mechanisms dictating satellite cell function following injury.

ABSTRACTPrior to the introduction ofHaemophilus influenzaetype b (Hib) conjugate vaccines, invasive Hib disease affected almost exclusively children. According to some recent studies, in the postvaccine era, adults, the elderly, and immunocompromised persons can be affected more often than children. As the production of type-specific anti-capsular polysaccharide antibodies is the major defense mechanism against Hib, individuals with defects in humoral immune responses have high susceptibility to infections caused by Hib. We hypothesized that nonvaccinated adults with chronic conditions causing immunosuppression may lack protective antibody to Hib. We assessed serum anti-Hib IgG levels and bactericidal activity in 59 patients with chronic renal failure, 30 patients with type 2 diabetes mellitus, 28 patients with chronic obstructive pulmonary disease (COPD), and 20 patients with multiple myeloma compared to 32 healthy controls of similar age. Considering antibody at >0.15 μg/ml as the protective correlate in unvaccinated individuals, we detected subprotective Hib antibody levels in 29% of chronic renal failure, 20% of diabetes, 14% of COPD, and 55% of myeloma patients compared to 3% of healthy controls. Additionally, 70% of myeloma and 58% of chronic renal failure patients did not have detectable serum bactericidal activity against Hib. Among individuals with severe diseases causing secondary immunodeficiency, patients with multiple myeloma and chronic renal failure are at an increased risk of invasive Hib disease. Considering that Hib continues to circulate in the population, this study provides a rationale for the immunization of some adult patients with secondary immunodeficiency with the pediatric Hib vaccine to achieve protective immunity.

Pseudomonas aeruginosa is the major cause of chronic pulmonary disease in cystic fibrosis (CF) patients. During chronic infection, P. aeruginosa lose certain virulence factors, transform into a mucoid phenotype, and develop antibiotic resistance. We hypothesized that these genetic and phenotypic alterations of P. aeruginosa affect the airway epithelial responses. A549 cells were infected with 27 well-characterized isolates of P. aeruginosa from CF patients obtained during longitudinal observation, or with P. aeruginosa mutant strains lacking flagella, pili, lipopolysaccharide, or pyocyanin. Pseudomonas aeruginosa isolates from the early stages of the infection exhibited high adherence to A549 cells, were readily internalized, and able to induce reactive oxygen species (ROS) production, apoptosis of infected cells, and the release of granulocyte macrophage colonystimulating factor. Late P. aeruginosa isolates collected from patients with chronic lung infection were shown to have reduced adherence to and internalization into A549 cells compared with bacteria from patients with intermittent P. aeruginosa colonization, and induced lower production of ROS and apoptosis, but caused high proinflammatory cytokine and adhesion molecule expression. Our findings suggest that despite the loss of virulence factors during the adaptation process in the CF lung by late P. aeruginosa strains, they retain high proinflammatory abilities that likely contribute to the disease pathogenesis.