Background-Obesity is associated with chronic inflammation, which includes increased macrophage accumulation in adipose tissue (AT) and upregulation of chemokines and cytokines. T cells also play important roles in chronic inflammatory diseases such as atherosclerosis but have not been well studied in obesity. Methods and Results-Flow cytometric analysis showed higher numbers of T cells and macrophages in AT of diet-induced obese insulin-resistant male mice than in lean mice and obese females (PϽ0.05). RNase protection assay, ELISA, and flow cytometry indicated gender-dependent upregulation of mRNA and protein levels of regulated on activation, normal T cell expressed and secreted (RANTES) and its receptor CCR5 in AT of obese mice. Adipocytes, stromal/vascular cells from mouse AT, and human and murine adipocytes expressed RANTES. RANTES mRNA levels were negatively correlated with adiponectin in mouse AT. Adiponectin-deficient mice fed high-fat diet showed higher RANTES mRNA levels in AT than wild-type mice. Activated T cells coincubated with preadipocytes in vitro significantly suppressed preadipocyte-to-adipocyte differentiation. Obese humans with metabolic syndrome had higher mRNA levels of RANTES and CCR5 in subcutaneous AT than lean humans. RANTES and CCR5 mRNA levels were significantly higher in visceral than subcutaneous AT of morbidly obese humans. RANTES mRNA levels were positively correlated with CD3 and CD11b in human visceral AT. Conclusions-Obesity is associated with increased accumulation of T cells and macrophages in AT, which may play important roles in obesity-related disease by influencing preadipocyte/adipocyte functions. RANTES is an adipokine that is upregulated in AT by obesity in both mice and humans.

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The pathophysiological functions of proline-glutamic acid (PE)/proline-proline-glutamic acid (PPE) family of proteins of Mycobacterium tuberculosis are not well understood. In this study, we demonstrate that one of the PPE proteins, PPE18 can stimulate macrophages to secrete IL-10, known to favor a Th2 type response. The recombinant PPE18 was found to specifically interact with the TLR2 leading to an early and sustained activation of p38 MAPK, which is critical for IL-10 induction. In silico docking analyses and mutation experiments indicate that PPE18 specifically interacts with the leucine rich repeat 11 approximately 15 domain of TLR2 and the site of interaction is different from that of a synthetic lipopeptide Pam(3)CSK(4) known to activate predominantly ERK 1/2. When PMA-differentiated THP-1 macrophages were infected with a mutant Mycobacterium tuberculosis strain lacking the PPE18, produced poorer levels of IL-10 as compared with those infected with the wild-type strain. In contrast, an M. smegmatis strain overexpressing the PPE18 induced higher levels of IL-10 in infected macrophages. Our data indicate that the PPE18 protein may trigger an anti-inflammatory response by inducing IL-10 production.

Phosphorylation of serine 51 residue on the alpha-subunit of eukaryotic initiation factor 2 (eIF2alpha) inhibits the guanine nucleotide exchange (GNE) activity of eIF2B, presumably, by forming a tight complex with eIF2B. Inhibition of the GNE activity of eIF2B leads to impairment in eIF2 recycling and protein synthesis. We have partially purified the wild-type (wt) and mutants of eIF2alpha in which the serine 51 residue was replaced with alanine (51A mutant) or aspartic acid (51D mutant) in the baculovirus system. Analysis of these mutants has provided novel insight into the role of 51 serine in the interaction between eIF2 and eIF2B. Neither mutant was phosphorylated in vitro. Both mutants decreased eIF2alpha phosphorylation occurring in hemin and poly(IC)-treated reticulocyte lysates due to the activation of double-stranded RNA-dependent protein kinase (PKR). However, addition of 51D, but not 51A mutant eIF2alpha protein promoted inhibition of the GNE activity of eIF2B in hemin-supplemented rabbit reticulocyte lysates in which relatively little or no endogenous eIF2alpha phosphorylation occurred. The 51D mutant enhanced the inhibition in GNE activity of eIF2B that occurred in hemin and poly(IC)-treated reticulocyte lysates where PKR is active. Our results show that the increased interaction between eIF2 and eIF2B protein, occurring in reticulocyte lysates due to increased eIF2alpha phosphorylation, is decreased significantly by the addition of mutant 51A protein but not 51D. Consistent with the idea that mutant 51D protein behaves like a phosphorylated eIF2alpha, addition of this partially purified recombinant subunit, but not 51A or wt eIF2alpha, increases the interaction between eIF2 and 2B proteins in actively translating hemin-supplemented lysates. These findings support the idea that phosphorylation of the serine 51 residue in eIF2alpha promotes complex formation between eIF2alpha(P) and eIF2B and thereby inhibits the GNE activity of eIF2B.