Prostanoid receptor 2 signaling protects T helper 2 cells from BALB/c mice against activation-induced cell death

Macrophage: A Cell With Many Faces and Functions in Tuberculosis

Mycobacterium tuberculosis (Mtb) is the causative agent of human tuberculosis (TB) which primarily infects the macrophages. Nearly a quarter of the world's population is infected latently by Mtb. Only around 5%-10% of those infected develop active TB disease, particularly during suppressed host immune conditions or comorbidity such as HIV, hinting toward the heterogeneity of Mtb infection. The aerosolized Mtb first reaches the lungs, and the resident alveolar macrophages (AMs) are among the first cells to encounter the Mtb infection. Evidence suggests that early clearance of Mtb infection is associated with robust innate immune responses in resident macrophages. In addition to lung-resident macrophage subsets, the recruited monocytes and monocyte-derived macrophages (MDMs) have been suggested to have a protective role during Mtb infection. Mtb, by virtue of its unique cell surface lipids and secreted protein effectors, can evade killing by the innate immune cells and preferentially establish a niche within the AMs. Continuous efforts to delineate the determinants of host defense mechanisms have brought to the center stage the crucial role of macrophage phenotypical variations for functional adaptations in TB. The morphological and functional heterogeneity and plasticity of the macrophages aid in confining the dissemination of Mtb. However, during a suppressed or hyperactivated immune state, the Mtb virulence factors can affect macrophage homeostasis which may skew to favor pathogen growth, causing active TB. This mini-review is aimed at summarizing the interplay of Mtb pathomechanisms in the macrophages and the implications of macrophage heterogeneity and plasticity during Mtb infection.

Expression profiles of prostaglandin E2 receptor subtypes in aspirin tolerant adult Chinese with chronic rhinosinusitis

BACKGROUND

Several studies have indicated that prostaglandin E2 and E-prostanoid (EP) receptors play a role in the pathogenesis of chronic rhinosinusitis (CRS) in white populations. However, until now there was no report about EP receptor expression and its role in the pathophysiology of CRS in Chinese patients.

OBJECTIVE

To investigate the expression profiles of EP receptors, including EP1, EP2, EP3, and EP4 receptors in different Chinese patients with CRS with aspirin tolerance.

METHODS

Nasal biopsy specimens were obtained from 12 controls, 12 patients with CRS without nasal polyps (CRSsNP), 12 with eosinophilic CRS with nasal polyps (CRSwNP), and 16 with noneosinophilic CRSwNP. Histopathologic characteristics were observed under a light microscope. Immunostaining was used to examine tissue localization of EP receptors. Messenger RNA and protein expression of EP receptors were examined by means of quantitative RT-polymerase chain reaction and Western blot, respectively.

RESULTS

Different types of CRS presented different histopathologic hallmarks. EP receptors were expressed mainly on epithelium, glands, and infiltrating inflammatory cells in nasal tissue. In controls, patients with CRSsNP, and those with noneosinophilic CRSwNP, EP4 mRNA levels were higher than EP1, EP2, and EP3 receptors. EP2 was downexpressed, and EP1 was upexpressed in patients with eosinophilic CRSwNP. When comparing EP receptor expression among different groups, Messenger RNA and protein of EP1 receptor were significantly enhanced in eosinophilic CRSwNP, but EP2, EP3, and EP4 receptors did not show significant differences.

CONCLUSION

EP receptor expressions present different features in healthy subjects and patients with CRS. The upregulated EP1 receptor in eosinophilic CRSwNP might be associated with excessive infiltrations of eosinophils and other inflammatory cells. The accurate role of the four EP receptors in the pathogenesis of different CRS remains to be further explored.

Arginase I, polyamine, and prostaglandin E2 pathways suppress the inflammatory response and contribute to diffuse cutaneous leishmaniasis

Diffuse cutaneous leishmaniasis (DCL) is a rare clinical manifestation of tegumentary leishmaniasis. The molecular mechanisms underlying DCL pathogenesis remain unclear, and there is no efficient treatment available. This study investigated the systemic and in situ expression of the inflammatory response that might contribute to suppression in DCL. The plasma levels of arginase I, ornithine decarboxylase (ODC), transforming growth factor β (TGF-β), and prostaglandin E2 (PGE2) were higher in patients with DCL, compared with patients with localized cutaneous leishmaniasis (LCL) or with controls from an area of endemicity. In situ transcriptomic analyses reinforced the association between arginase I expression and enzymes involved in prostaglandin and polyamine synthesis. Immunohistochemistry confirmed that arginase I, ODC, and cyclooxygenase2 expression was higher in lesion biopsy specimens from patients with DCL than in those from patients with LCL. Inhibition of arginase I or ODC abrogates L. amazonensis replication in infected human macrophages. Our data implicate arginase I, ODC, PGE2, and TGF-β in the failure to mount an efficient immune response and suggest perspectives in the development of new strategies for therapeutic intervention for patients with DCL.

Polyunsaturated Fatty Acid-derived lipid mediators and T cell function

Fatty acids are involved in T cell biology both as nutrients important for energy production as well as signaling molecules. In particular, polyunsaturated fatty acids are known to exhibit a range of immunomodulatory properties that progress through T cell mediated events, although the molecular mechanisms of these actions have not yet been fully elucidated. Some of these immune activities are linked to polyunsaturated fatty acid-induced alteration of the composition of cellular membranes and the consequent changes in signaling pathways linked to membrane raft-associated proteins. However, significant aspects of the polyunsaturated fatty acid bioactivities are mediated through their transformation to specific lipid mediators, products of cyclooxygenase, lipoxygenase, or cytochrome P450 enzymatic reactions. Resulting bioactive metabolites including prostaglandins, leukotrienes, and endocannabinoids are produced by and/or act upon T leukocytes through cell surface receptors and have been shown to alter T cell activation and differentiation, proliferation, cytokine production, motility, and homing events. Detailed appreciation of the mode of action of these lipids presents opportunities for the design and development of therapeutic strategies aimed at regulating T cell function.

An important role of prostanoid receptor EP2 in host resistance to Mycobacterium tuberculosis infection in mice

Mycobacterium tuberculosis, the causative agent of tuberculosis, resides and replicates within susceptible hosts by inhibiting host antimicrobial mechanisms. Prostaglandin E(2) (PGE(2)), produced by M. tuberculosis-infected macrophages, exerts a variety of immunomodulatory functions via 4 receptors (EP1-EP4), each mediating distinct PGE(2) functions. Here, we show that M. tuberculosis infection selectively upregulates EP2 messenger RNA expression in CD4(+) T cells. We found that EP2 deficiency in mice increases susceptibility to M. tuberculosis infection, which correlated with reduced antigen-specific T-cell responses and increased levels of CD4(+)CD25(+)Foxp3(+) T-regulatory cells. These findings have revealed an important role for EP2 in host immune defense against tuberculosis. As a G protein-coupled receptor, EP2 could serve as a target for immunotherapy of tuberculosis.