Role of TIM-4 in innate or adaptive immune response

Targeting macrophages in atherosclerosis using nanocarriers loaded with liver X receptor agonists: A narrow review

Macrophages are involved in the whole process of atherosclerosis, which is characterized by accumulation of lipid and inflammation. Presently, clinically used lipid-lowering drugs cannot completely retard the progress of atherosclerosis. Liver X receptor (LXR) plays a key role in regulation of lipid metabolism and inflammation. Accumulating evidence have demonstrated that synthetic LXR agonists can significantly retard the development of atherosclerosis. However, these agonists induce sever hypertriglyceridemia and liver steatosis. These side effects have greatly limited their potential application for therapy of atherosclerosis. The rapid development of drug delivery system makes it possible to delivery interested drugs to special organs or cells using nanocarriers. Macrophages express various receptors which can recognize and ingest specially modified nanocarriers loaded with LXR agonists. In the past decades, a great progress has been made in this field. These macrophage-targeted nanocarriers loaded with LXR agonists are found to decrease atherosclerosis by reducing cholesterol accumulation and inflammatory reactions. Of important, these nanocarriers can alleviate side effects of LXR agonists. In this article, we briefly review the roles of macrophages in atherosclerosis, mechanisms of action of LXR agonists, and focus on the advances of macrophage-targeted nanocarriers loaded with LXR agonists. This work may promote the potential clinical application of these nanocarriers.

Lentinan diminishes apoptotic bodies in the ileal crypts associated with S-1 administration

S-1 is an oral agent containing tegafur (a prodrug of 5-fluorouracil) that is used to treat various cancers, but adverse effects are frequent. Two pilot clinical studies have suggested that lentinan (LNT; β-1,3-glucan) may reduce the incidence of adverse effects caused by S-1 therapy. In this study, we established a murine model for assessment of gastrointestinal toxicity associated with S-1 and studied the effect of LNT. S-1 was administered orally to BALB/c mice at the effective dose (8.3mg/kg, as tegafur equivalent) once daily (5days per week) for 3weeks. Stool consistency and intestinal specimens were examined. We investigated the effect of combined intravenous administration of LNT at 0.1mg, which is an effective dose in murine tumor models. We also investigated the effect of a single administration of S-1. During long-term administration of S-1, some mice had loose stools and an increase in apoptotic bodies was observed in the ileal crypts. An increase in apoptotic bodies was also noted after a single administration of S-1 (15mg/kg). Prior or concomitant administration of LNT inhibited the increase in apoptotic bodies in both settings. Administration of LNT also increased the accumulation of CD11b⁺TIM-4⁺ cells in the ileum, while depletion of these cells by liposomal clodronate diminished the inhibitory effect of LNT on S-1 toxicity. Combined administration of LNT with S-1 led to a decrease in apoptotic bodies in the ileal crypts, possibly because LNT promoted phagocytosis of damaged cells by CD11b⁺TIM-4⁺ cells.

Immune Regulation and Antitumor Effect of TIM-1

T cells play an important role in antitumor immunity, and the T cell immunoglobulin domain and the mucin domain protein-1 (TIM-1) on its surface, as a costimulatory molecule, has a strong regulatory effect on T cells. TIM-1 can regulate and enhance type 1 immune response of tumor association. Therefore, TIM-1 costimulatory pathways may be a promising therapeutic target in future tumor immunotherapy. This review describes the immune regulation and antitumor effect of TIM-1.

TIM-1 rs41297579 G>A (-1454) and TIM-4 rs7700944 gene polymorphisms as possible risk factor for rheumatoid arthritis: relation to activity and severity

This study was aimed to evaluate the impact of both TIM-1 rs41297579 G>A (-1454) and TIM-4 rs7700944 polymorphisms on susceptibility to rheumatoid arthritis (RA) in a cohort of Egyptian population and to evaluate for the first time their relation to activity, severity, disease-related disability and erosion. TIM-1 rs41297579 G>A (-1454) and TIM-4 rs7700944 gene polymorphisms were typed by RFLP for 128 patients with RA and 125 healthy controls. The A allele, A-containing genotypes (GA and AA) of the TIM-4 and GA haplotype were present with significant higher frequency in patients with RA than healthy controls (Pc  < 0.001). These findings suggest that the A allele, A-containing genotypes (GA and AA) and GA haplotype may be a susceptibility risk factor for RA [OR = 5.83 (3.6-9.4), OR = 9.41 (5.0-17.6) and OR = 4.21 (1.07-19.2), respectively]. No associations were found between TIM genotypes and disease activity, severity or presence of erosion. However, the RA patients with GA genotype of TIM-4 have higher grade of rheumatoid factor (RF) positivity (P = 0.018), and have worse disease-related disability (P = 0.007) and worse pain (0.025). TIM-4 rs7700944 and not TIM-1 rs41297579 G>A (-1454) is associated with RA in the present cohort of Egyptian and may be a risk factor for development of RA in Egyptian. Both SNPs have no effect on disease activity, severity or erosion. However, TIM-4 GA genotype is associated with higher grade of RF positivity and worse disease-related disability and pain.

TIM4 Regulates the Anti-Islet Th2 Alloimmune Response

The role of the novel costimulatory molecule TIM4 in anti-islet response is unknown. We explored TIM4 expression and targeting in Th1 (BALB/c islets into C57BL/6 mice) and Th2 (BALB/c islets into Tbet(-/-) C57BL/6 mice) models of anti-islet alloimmune response and in a model of anti-islet autoimmune response (diabetes onset in NOD mice). The targeting of TIM4, using the monoclonal antibody RMT4-53, promotes islet graft survival in a Th1 model, with 30% of the graft surviving in the long term; islet graft protection appears to be mediated by a Th1 to Th2 skewing of the immune response. Differently, in the Th2 model, TIM4 targeting precipitates graft rejection by further enhancing the Th2 response. The effect of anti-TIM4 treatment in preventing autoimmune diabetes was marginal with only minor Th1 to Th2 skewing. B-Cell depletion abolished the effect of TIM4 targeting. TIM4 is expressed on human B-cells and is upregulated in diabetic and islet-transplanted patients. Our data suggest a model in which TIM4 targeting promotes Th2 response over Th1 via B-cells. The targeting of TIM4 could become a component of an immunoregulatory protocol in clinical islet transplantation, aiming at redirecting the immune system toward a Th2 response.

Oxidatively modified phosphatidylserines on the surface of apoptotic cells are essential phagocytic 'eat-me' signals: cleavage and inhibition of phagocytosis by Lp-PLA2

Diversified anionic phospholipids, phosphatidylserines (PS), externalized to the surface of apoptotic cells are universal phagocytic signals. However, the role of major PS metabolites, such as peroxidized species of PS (PSox) and lyso-PS, in the clearance of apoptotic cells has not been rigorously evaluated. Here, we demonstrate that H2O2 was equally effective in inducing apoptosis and externalization of PS in naive HL60 cells and in cells enriched with oxidizable polyunsaturated species of PS (supplemented with linoleic acid (LA)). Despite this, the uptake of LA-supplemented cells by RAW264.7 and THP-1 macrophages was more than an order of magnitude more effective than that of naive cells. A similar stimulation of phagocytosis was observed with LA-enriched HL60 cells and Jurkat cells triggered to apoptosis with staurosporine. This was due to the presence of PSox on the surface of apoptotic LA-supplemented cells (but not of naive cells). This enhanced phagocytosis was dependent on activation of the intrinsic apoptotic pathway, as no stimulation of phagocytosis occurred in LA-enriched cells challenged with Fas antibody. Incubation of apoptotic cells with lipoprotein-associated phospholipase A2 (Lp-PLA2), a secreted enzyme with high specificity towards PSox, hydrolyzed peroxidized PS species in LA-supplemented cells resulting in the suppression of phagocytosis to the levels observed for naive cells. This suppression of phagocytosis by Lp-PLA2 was blocked by a selective inhibitor of Lp-PLA2, SB-435495. Screening of possible receptor candidates revealed the ability of several PS receptors and bridging proteins to recognize both PS and PSox, albeit with diverse selectivity. We conclude that PSox is an effective phagocytic 'eat-me' signal that participates in the engulfment of cells undergoing intrinsic apoptosis.

Ubiquitin E3 ligase TNFIAP3 mediates endosome/lysosome fusion in nasal epithelial cells

The nasal epithelial barrier dysfunction is associated with the pathogenesis of nasal allergy; the causative factors are to be further elucidated. Ubiquitin E3 ligase TNFIAP3 (TNFIAP3, in short) plays a role in the maintenance of the homeostasis in the body. This study aims to elucidate the role of TNFIAP3 in the degradation of endocytic substances in nasal epithelial cells. The nasal epithelial cell line, RPMI 2650 cells (RPC), was cultured into monolayers in transwells. The endocytosis of staphylococcal enterotoxin B (SEB) by RPC monolayers was assessed by enzyme-linked immunoassay. The endocytosis of SEB-triggered endosome/lysosome fusion was observed by immunocytochemistry. The results showed that RPC monolayers expressed TNFIAP3 upon the endocytosis of SEB. Deficiency of TNFIAP3 resulted in abundant SEBs being transported to the basal chambers of transwells via the intracellular pathway. In the TNFIAP3-sufficient RPC, SEB-carrying endosomes fused with lysosomes were observed. The TNFIAP3-deficient RPC showed few SEB-carrying endosomes fused with lysosomes. In summary, TNFIAP3 plays an important role in tethering endosomes to lysosomes in RPC.