Elevated cyclic AMP and PDE4 inhibition induce chemokine expression in human monocyte-derived macrophages.

Macrophages are central mediators of the innate immune system that can be differentiated from monocytes upon exposure to cytokines. While increased cyclic adenosine monophosphate (cAMP) levels are known to inhibit many lipopolysaccharide-elicited macrophage inflammatory responses, the effects of elevated cAMP on monocyte/macrophage differentiation are not as well understood. We show here that during differentiation, cAMP agonists can cause a large increase in the mRNA and protein levels of several of the pro-inflammatory CXCL and CCL chemokines. The cAMP mediator-exchange protein activated by cAMP (Epac) contributes substantially to the increase in these chemokines. These chemokines are known to play an important role in the regulation of immune responses, particularly regarding the pathogenesis of asthma and chronic obstructive pulmonary disorder. We also found that a selective cAMP-degrading phosphodiesterase (PDE) 4 inhibitor can potentiate the chemokine expression elicited by low-dose forskolin or Prostaglandin E2 (PGE(2)). These data suggest that chemokine receptor antagonists administered in conjunction with a PDE4 inhibitor may improve both the efficacy and safety of PDE4-inhibitor therapy for chronic inflammatory disorders.

Primary tuberculosis of bone mimicking a lytic bone tumor.

Causes of lytic bone lesions in children include benign, malignant, and infectious processes. Here, we present the case of a 3-year-old boy presenting with a lytic bone lesion and surrounding soft tissue mass sent for evaluation of possible malignancy versus osteomyelitis. Biopsy revealed granulomatous osteomyelitis, and subsequent purified protein derivative resulted in 20-mm induration. Lesion cultures eventually identified pan-sensitive Mycobacterium tuberculosis. We emphasize that tuberculosis can cause primary lytic bone lesions in children in the United States, even in the absence of pulmonary symptoms or known exposure, and advise clinicians to include mycobacterial cultures when analyzing biopsies of lytic bone lesions.

Dynamic anchoring of PKA is essential during oocyte maturation.

In the final stages of ovarian follicular development, the mouse oocyte remains arrested in the first meiotic prophase, and cAMP-stimulated PKA plays an essential role in this arrest. After the LH surge, a decrease in cAMP and PKA activity in the oocyte initiates an irreversible maturation process that culminates in a second arrest at metaphase II prior to fertilization. A-kinase anchoring proteins (AKAPs) mediate the intracellular localization of PKA and control the specificity and kinetics of substrate phosphorylation. Several AKAPs have been identified in oocytes including one at 140 kDa that we now identify as a product of the Akap1 gene. We show that PKA interaction with AKAPs is essential for two sequential steps in the maturation process: the initial maintenance of meiotic arrest and the subsequent irreversible progression to the polar body extruded stage. A peptide inhibitor (HT31) that disrupts AKAP/PKA interactions stimulates oocyte maturation in the continued presence of high cAMP. However, during the early minutes of maturation, type II PKA moves from cytoplasmic sites to the mitochondria, where it associates with AKAP1, and this is shown to be essential for maturation to continue irreversibly.

Alleles of the NRAMP1 gene are risk factors for pediatric tuberculosis disease.

Relatively little is known about the human genetics of susceptibility to common diseases caused by bacterial pathogens. Tuberculosis, caused by Mycobacterium tuberculosis, is a major cause of morbidity and mortality worldwide. So far, genetic studies of tuberculosis susceptibility have largely been focused on adult patients despite the fact that tuberculosis is highly prevalent among children. To study the host genetic component of pediatric tuberculosis susceptibility, we enrolled 184 ethnically diverse families from the Greater Houston area with at least one child affected by pediatric tuberculosis disease. Using a family-based control design, we found allelic variants of the natural resistance-associated macrophage protein gene 1 (NRAMP1) (alias SLC11A1) significantly associated with tuberculosis disease in this pediatric patient population [P = 0.01; odds ratio = 1.75 (95% confidence interval, 1.10-2.77)]. The association of NRAMP1 with pediatric tuberculosis disease was significantly heterogeneous (P = 0.01) between simplex [P <0.0008; odds ratio = 3.13 (1.54-6.25)] and multiplex families (P = 1), suggesting an interplay between mechanisms of genetic control and exposure intensities. In striking contrast to previous studies in the adult population, we observed that the common alleles of NRAMP1 polymorphisms were risk factors for pediatric tuberculosis disease. To explain the different direction of allelic association between adult and pediatric disease, we hypothesize that NRAMP1 influences the speed of progression from infection to tuberculosis disease.