Tim-4 Inhibits NO Generation by Murine Macrophages

Abstract

ObjectiveT cell immunoglobulin- and mucin-domain-containing molecule-4 (Tim-4) receives much attention as a potentially negative regulator of immune responses. However, its modulation on macrophages has not been fully elucidated so far. This study aimed to identify the role of Tim-4 in nitric oxide (NO) modulation.MethodsMacrophages were stimulated with 100 ng/ml LPS or 100 U/ml IFN-γ. RT-PCR was performed to detect TIM-4 mRNA expression. Tim-4 blocking antibody and NF-κB inhibitory ligand were involved in the study. NO levels were assayed by Griess reaction. Phosphorylation of NF-κB, Jak2 or Stat1 was verified by western blot.ResultsTim-4 was up-regulated in murine macrophages after interferon-gamma (IFN-γ) stimulation. Tim-4 over-expression decreased NO production and inducible nitric oxide synthase (iNOS) expression in lipopolysaccharide (LPS) or IFN-γ-stimulated macrophages. Consistently, Tim-4 blockade promoted LPS or IFN-γ-induced NO secretion and iNOS expression. Tim-4 over-expression decreased LPS-induced nuclear factor kappa B (NF-κB) p65 phosphorylation in macrophages, which was abrogated by NF-κB inhibitory ligand. On the contrary, Tim-4 blocking increased LPS-induced NF-κB signaling, which was also abrogated by NF-κB inhibition. In addition, Tim-4 blockade promoted Jak2 and Stat1 phosphorylation in IFN-γ stimulated macrophages.ConclusionThese results indicate that Tim-4 is involved in negative regulation of NO production in macrophages, suggesting the critical role of Tim-4 in immune related diseases.

Tim-4 in Health and Disease: Friend or Foe?

“…Although Con A-induced liver injury is a T cellmediated autoimmune hepatitis model (36), it has been found that Kupffer cells are involved in the initiation and propagation of liver damages (37), suggesting that Tim-4 expressed on macrophages might attenuate the priming and activation of T cell responses in Con A-induced hepatitis. Further analysis showed that Tim-4 inhibited cytokines and NO production via the NF-κB or Jak2/STAT1 signaling pathways (14). Taken together, we speculate that Tim-4 may play an inhibitory role in the course of macrophage activation.…”

“…We reported that Tim-4 inhibited the expression of CD80, CD86, MHC-II and the production of TNF-α in LPS-treated macrophages (15). Tim-4 could also suppress nitric oxide (NO) production in LPS-or IFN-γ-activated macrophages (14). Furthermore, Tim-4 was shown to protect mice from ConA-induced liver injury or LPS-induced septic shock by inhibiting pro-inflammatory cytokines such as IL-6 and TNFα (15,35).…”

“…It has been confirmed that Tim-4 is selectively expressed in macrophages, mature dendritic cells (DCs), peritoneal B1 cells, and invariant natural killer T (iNKT) cells (9,11). Furthermore, the levels of Tim-4 expression can be regulated by different stimulators, such as lipopolysaccharide (LPS), cholera toxins, cytokines, Concanavalin A (ConA), and danger associated molecular patterns (DAMPs) (12)(13)(14)(15)(16). However, Tim-4 expression can also be downregulated under some conditions.…”

IL‐6 promotes metastasis of non‐small‐cell lung cancer by up‐regulating TIM‐4 via NF‐κB

“…Our previous studies showed that LPS, IFN-γ and ConA could enhance TIM-4 expression in macrophages. 23,24 It was also reported that damage-associated molecular patterns released from chemotherapy-damaged tumour cells induced TIM-4 expression on tumour-associated macrophages and dendritic cells. 25 Recent studies have shown that TIM-4 is overexpressed in several tumours, 26,27 which is related with the worse prognosis of lung cancer as PD-L1, which further aggravated the tumour development.…”

Stauntoside B inhibits macrophage activation by inhibiting NF-κB and ERK MAPK signalling

“…Nuclear factor-κB (NF-κB), a vital activator in inflammatory processes, can regulate the expression of inflammatory cytokines and mediators, and chemokines in many cell types, including macrophages [19][20][21]. Under normal condition of cells, NF-κB exists in an inactive form by combining with its inhibitory protein (IκB) in the cytoplasm.…”