T-cell activation is enhanced by targeting IL-10 cytokine production in toll-like receptor-stimulated macrophages

Myeloid cell-derived PROS1 inhibits tumor metastasis by regulating inflammatory and immune responses via IL-10

Stimulation of TAM (TYRO3, AXL, and MERTK) receptor tyrosine kinases promotes tumor progression through numerous cellular mechanisms. TAM cognate ligands GAS6 and PROS1 (for TYRO3 and MERTK) are secreted by host immune cells, an interaction which may support tumor progression. Here, we revealed an unexpected antimetastatic role for myeloid-derived PROS1: suppressing metastatic potential in lung and breast tumor models. Pros1 deletion in myeloid cells led to increased lung metastasis, independent of primary tumor infiltration. PROS1-cKO bone marrow-derived macrophages (BMDMs) led to elevated TNF-α, IL-6, Nos2, and IL-10 via modulation of the Socs3/NF-κB pathway. Conditioned medium from cKO BMDMs enhanced EMT, ERK, AKT, and STAT3 activation within tumor cells and promoted IL-10-dependent invasion and survival. Macrophages isolated from metastatic lungs modulated T cell proliferation and function, as well as expression of costimulatory molecules on DCs in a PROS1-dependent manner. Inhibition of MERTK kinase activity blocked PROS1-mediated suppression of TNF-α and IL-6 but not IL-10. Overall, using lung and breast cancer models, we identified the PROS1/MERTK axis within BMDMs as a potent regulator of adaptive immune responses with a potential to suppress metastatic seeding and revealed IL-10 regulation by PROS1 to deviate from that of TNF-α and IL-6.

Dysregulation of sphingolipid metabolism contributes to bortezomib-induced neuropathic pain

The development of chemotherapy-induced painful peripheral neuropathy is a major dose-limiting side effect of many chemotherapeutics, including bortezomib, but the mechanisms remain poorly understood. We now report that bortezomib causes the dysregulation of de novo sphingolipid metabolism in the spinal cord dorsal horn to increase the levels of sphingosine-1-phosphate (S1P) receptor 1 (S1PR1) ligands, S1P and dihydro-S1P. Accordingly, genetic and pharmacological disruption of S1PR1 with multiple S1PR1 antagonists, including FTY720, blocked and reversed neuropathic pain. Mice with astrocyte-specific alterations of S1pr1 did not develop neuropathic pain and lost their ability to respond to S1PR1 inhibition, strongly implicating astrocytes as a primary cellular substrate for S1PR1 activity. At the molecular level, S1PR1 engaged astrocyte-driven neuroinflammation and altered glutamatergic homeostasis, processes blocked by S1PR1 antagonism. Our findings establish S1PR1 as a target for therapeutic intervention and provide insight into cellular and molecular pathways. As FTY720 also shows promising anticancer potential and is FDA approved, rapid clinical translation of our findings is anticipated.

Vitamin d deficiency reduces the immune response, phagocytosis rate, and intracellular killing rate of microglial cells

Meningitis and meningoencephalitis caused by Escherichia coli are associated with high rates of mortality and neurological sequelae. A high prevalence of neurological disorders has been observed in geriatric populations at risk of hypovitaminosis D. Vitamin D has potent effects on human immunity, including induction of antimicrobial peptides (AMPs) and suppression of T-cell proliferation, but its influence on microglial cells is unknown. The purpose of the present study was to determine the effects of vitamin D deficiency on the phagocytosis rate, intracellular killing, and immune response of murine microglial cultures after stimulation with the Toll-like receptor (TLR) agonists tripalmitoyl-S-glyceryl-cysteine (TLR1/2), poly(I·C) (TLR3), lipopolysaccharide (TLR4), and CpG oligodeoxynucleotide (TLR9). Upon stimulation with high concentrations of TLR agonists, the release of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) was decreased in vitamin D-deficient compared to that in vitamin D-sufficient microglial cultures. Phagocytosis of E. coli K1 after stimulation of microglial cells with high concentrations of TLR3, -4, and -9 agonists and intracellular killing of E. coli K1 after stimulation with high concentrations of all TLR agonists were lower in vitamin D-deficient microglial cells than in the respective control cells. Our observations suggest that vitamin D deficiency may impair the resistance of the brain against bacterial infections.