Chanzyme TRPM7 Mediates the Ca2+ Influx Essential for Lipopolysaccharide-Induced Toll-Like Receptor 4 Endocytosis and Macrophage Activation.

Toll-like receptors (TLRs) sense pathogen-associated molecular patterns to activate the production of inflammatory mediators. TLR4 recognizes lipopolysaccharide (LPS) and drives the secretion of inflammatory cytokines, often contributing to sepsis. We report that transient receptor potential melastatin-like 7 (TRPM7), a non-selective but Ca2+-conducting ion channel, mediates the cytosolic Ca2+ elevations essential for LPS-induced macrophage activation. LPS triggered TRPM7-dependent Ca2+ elevations essential for TLR4 endocytosis and the subsequent activation of the transcription factor IRF3. In a parallel pathway, the Ca2+ signaling initiated by TRPM7 was also essential for the nuclear translocation of NFκB. Consequently, TRPM7-deficient macrophages exhibited major deficits in the LPS-induced transcriptional programs in that they failed to produce IL-1ß and other key pro-inflammatory cytokines. In accord with these defects, mice with myeloid-specific deletion of Trpm7 are protected from LPS-induced peritonitis. Our study highlights the importance of Ca2+ signaling in macrophage activation and identifies the ion channel TRPM7 as a central component of TLR4 signaling.

Endothelial dysfunction and risk factors for atherosclerosis in psoriatic arthritis: overview and comparison with rheumatoid arthritis.

Endothelial dysfunction (ED) is defined as an impairment in the vasodilatory, anti-thrombotic, and anti-inflammatory properties of the cells that make up the lining of blood vessels. ED is considered a key step in the development of atherosclerotic cardiovascular disease. The association between ED and systemic inflammatory diseases is well established. However, the prevalence and clinical significance of ED in psoriatic arthritis (PsA) have been investigated to a lesser extent. This review aims to explore the link between ED and PsA, including ED in macro- and microcirculation, as well as risk factors for its occurrence in PsA and its relationship with atherosclerosis in PsA. Furthermore, the ED in PsA was compared with that of rheumatoid arthritis (RA). Regarding ED in the microcirculation, the coronary flow reserve was found to be significantly reduced in individuals with PsA. The relationship between PsA and macrovascular ED is more pronounced, along with more advanced atherosclerosis detected in patients with PsA. These results are consistent with those obtained in RA studies. On the other hand, arterial stiffness and signs of vascular remodeling were found more frequently in RA than in PsA, with the potential role of efficient anti-TNF treatment in patients with PsA and psoriasis explaining this finding. The impact of ED on cardiovascular diseases and the burden of this risk caused independently by PsA have not yet been precisely established, however, this group of patients requires special attention with regard to cardiovascular events.

Targeting the ion channel TRPM7 promotes the thymic development of regulatory T cells by promoting IL-2 signaling.

The thymic development of regulatory T (Treg) cells, crucial suppressors of the responses of effector T (Teff) cells, is governed by the transcription factor FOXP3. Despite the clinical importance of Treg cells, there is a dearth of druggable molecular targets capable of increasing their numbers in vivo. We found that inhibiting the function of the TRPM7 chanzyme (ion channel and enzyme) potentiated the thymic development of Treg cells in mice and led to a substantially higher frequency of functional Treg cells in the periphery. In addition, TRPM7-deficient mice were resistant to T cell-driven hepatitis. Deletion of Trpm7 and inhibition of TRPM7 channel activity by the FDA-approved drug FTY720 increased the sensitivity of T cells to the cytokine interleukin-2 (IL-2) through a positive feed-forward loop involving increased expression of the IL-2 receptor α-subunit and activation of the transcriptional regulator STAT5. Enhanced IL-2 signaling increased the expression of Foxp3 in thymocytes and promoted thymic Treg (tTreg) cell development. Thus, these data indicate that inhibiting TRPM7 activity increases Treg cell numbers, suggesting that it may be a therapeutic target to promote immune tolerance.

Hematopoietic pannexin 1 function is critical for neuropathic pain.

Neuropathic pain symptoms respond poorly to available therapeutics, with most treated patients reporting unrelieved pain and significant impairment in daily life. Here, we show that Pannexin 1 (Panx1) in hematopoietic cells is required for pain-like responses following nerve injury in mice, and a potential therapeutic target. Panx1 knockout mice (Panx1-/-) were protected from hypersensitivity in two sciatic nerve injury models. Bone marrow transplantation studies show that expression of functional Panx1 in hematopoietic cells is necessary for mechanical hypersensitivity following nerve injury. Reconstitution of irradiated Panx1 knockout mice with hematopoietic Panx1-/- cells engineered to re-express Panx1 was sufficient to recover hypersensitivity after nerve injury; this rescue required expression of a Panx1 variant that can be activated by G protein-coupled receptors (GPCRs). Finally, chemically distinct Panx1 inhibitors blocked development of nerve injury-induced hypersensitivity and partially relieved this hypersensitivity after it was established. These studies indicate that Panx1 expressed in immune cells is critical for pain-like effects following nerve injury in mice, perhaps via a GPCR-mediated activation mechanism, and suggest that inhibition of Panx1 may be useful in treating neuropathic pain.