Inhibition of TIM-4 protects against cerebral ischaemia-reperfusion injury

Phosphatidylserine in the Nervous System: Cytoplasmic Regulator of the AKT and PKC Signaling Pathways and Extracellular "Eat-Me" Signal in Microglial Phagocytosis

Phosphatidylserine (PtdSer) is an important anionic phospholipid found in eukaryotic cells and has been proven to serve as a beneficial factor in the treatment of neurodegenerative diseases. PtdSer resides in the inner leaflet of the plasma membrane, where it is involved in regulating the AKT and PKC signaling pathways; however, it becomes exposed to the extracellular leaflet during neurodevelopmental processes and neurodegenerative diseases, participating in microglia-mediated synaptic and neuronal phagocytosis. In this paper, we review several characteristics of PtdSer, including the synthesis and translocation of PtdSer, the functions of cytoplasmic and exposed PtdSer, and different PtdSer-detection materials used to further understand the role of PtdSer in the nervous system.

Function and characteristics of TIM‑4 in immune regulation and disease (Review)

T‑cell/transmembrane immunoglobulin and mucin domain containing 4 (TIM‑4) is a phosphatidylserine receptor that is mainly expressed on antigen‑presenting cells and is involved in the recognition and efferocytosis of apoptotic cells. TIM‑4 has been found to be expressed in immune cells such as natural killer T, B and mast cells and to participate in multiple aspects of immune regulation, suggesting that TIM‑4 may be involved in a variety of immune‑related diseases. Recent studies have confirmed that TIM‑4 is also abnormally expressed in a variety of malignant tumor cells and is closely associated with the occurrence and development of tumors and the tumor immune microenvironment. The present study aimed to describe the expression and functional characteristics of TIM‑4 in detail and to comprehensively discuss its role in pathophysiological processes such as infection, allergy, metabolism, autoimmunity and tumor immunity. The current review provided a comprehensive understanding of the functions and characteristics of TIM‑4, as well as novel ideas for the diagnosis and treatment of diseases.

Long Non-coding RNA ANRIL Downregulation Alleviates Neuroinflammation in an Ischemia Stroke Model via Modulation of the miR-671-5p/NF-κB Pathway

The aim of this study was to investigate the role and underlying mechanism of the long non-coding RNA ANRIL (antisense noncoding RNA in the INK4 locus, ANRIL) in ischemia stroke (IS) injury. Downregulation of ANRIL by right intracerebroventricular injected si-ANRIL in middle cerebral artery occlusion-reperfusion (MCAO/R) C57/BL6 mice and by transferring si-ANRIL in oxygen glucose deprivation/reperfusion (OGD/R) HT22 cells. The results showed that ANRIL levels increased in IS model, downregulation of ANRIL reduced infract area, neurological deficit scores and injured cells, and prolong fall latency time in MCAO/R mice, improved cell viability and reduced cell cytotoxicity in OGD/R cells. Fluorescence in Situ Hybridization detected that there were both ANRIL and miR-671-5p in neurons; miranda v3.3a and dual luciferase reporter assay demonstrated that miR-671-5p was one of direct target of ANRIL; and our previously published research demonstrated that NF-κB was one of direct target of miR-671-5p. Downregulation of ANRIL alleviated neuroinflammation and reduced p-NF-κB, NF-κB, pro-inflammatory cytokines (IL-1β, IL-6, TNF-a), and iNOS, which diminished by miR-671-5p antagomir both in in vivo and in vitro IS models. Downregulation of ANRIL alleviated disruption of blood brain barrier, and protected against tight junction (ZO-1, occludin and claudin 5) disorder in MCAO/R mice. This work clarified that downregulation of ANRIL reduced neuroinflammation by negatively regulating miR-671-5p to inhibit NF-κB in IS models, which provided a theoretical foundation for the protective effect of downregulating ANRIL for IS patients.

T-Cell Immunoglobulin and Mucin Domain-Containing Protein-4 Is Critical for Kupffer Cell Homeostatic Function in the Activation and Resolution of Liver Ischemia Reperfusion Injury

BACKGROUND AND AIMS

Liver ischemia reperfusion injury (IRI) remains an unresolved clinical problem. This study dissected roles of liver-resident macrophage Kupffer cells (KCs), with a functional focus on efferocytosis receptor T-cell immunoglobulin and mucin domain-containing protein-4 (TIM-4), in both the activation and resolution of IRI in a murine liver partial warm ischemia model.

APPROACH AND RESULTS

Fluorescence-activated cell sorting results showed that TIM-4 was expressed exclusively by KCs, but not infiltrating macrophages (iMФs), in IR livers. Anti-TIM-4 antibody depleted TIM-4⁺ macrophages in vivo, resulting in either alleviation or deterioration of liver IRI, which was determined by the repopulation kinetics of the KC niche with CD11b⁺ macrophages. To determine the KC-specific function of TIM-4, we reconstituted clodronate-liposome-treated mice with exogenous wild-type or TIM-4-deficient KCs at either 0 hour or 24 hours postreperfusion. TIM-4 deficiency in KCs resulted in not only increases in the severity of liver IRI (at 6 hours postreperfusion), but also impairment of the inflammation resolution (at 7 days postreperfusion). In vitro analysis revealed that TIM-4 promoted KC efferocytosis to regulate their Toll-like receptor response by up-regulating IL-10 and down-regulating TNF-α productions.

CONCLUSIONS

TIM-4 is critical for KC homeostatic function in both the activation and resolution of liver IRI by efferocytosis.

miR-671-5p Attenuates Neuroinflammation via Suppressing NF-κB Expression in an Acute Ischemic Stroke Model

This study was designed to investigate the role of miR-671-5p in in vitro and in vivo models of ischemic stroke (IS). Middle cerebral artery occlusion and reperfusion (MCAO/R) in C57BL/6 mice as well as oxygen-glucose deprivation and reoxygenation (OGD/R) in a mouse hippocampal HT22 neuron line were used as in vivo and in vitro models of IS injury, respectively. miR-671-5p agomir, miR-671-5p antagomir, pcDNA3.1-NF-κB, and negative controls were transfected into cells using riboFECT CP reagent. miR-671-5p agomir, pcDNA3.1-NF-κB, and negative vectors were administered into MCAO/R mice via intracerebroventricular injection. The results showed that miR-671-5p was significantly downregulated and that miR-671-5p agomir alleviated injury and neuroinflammation induced by ischemic reperfusion. A dual-luciferase reporter assay confirmed that NF-κB is a direct target of miR-671-5p. Reverse experiments showed that miR-671-5p agomir reduced neuroinflammation via suppression of NF-κB expression in both in vitro and in vivo models of IS. Our data suggest that miR-671-5p may be a viable therapeutic target for diminishing neuroinflammation in patients with IS.

A modified protocol for isolation of retinal microglia from the pig

Microglia are the resident immune cells in the retina. To investigate their properties and behaviour, a reliable and yielding procedure to culture them is necessary. We here describe a way of isolation of microglial cells from the porcine retina, as pig eyes are similar to human eyes in size, structure and vasculature, including similarities in proteins and pathways. Retina was isolated from fresh pig eyes, dissociated by a mixture of collagenase, hyaluronidase and DNAse, and passed through a cell strainer. After triple centrifugation with decreasing velocity and re-suspension, cells were seeded into poly-d-lysine coated culture flasks and cultured using DMEM and macrophage-colony stimulating factor (M-CSF). Number of cells increased gradually during the first 10-14 days, till they could be split and used for experiments. Identity of isolated cells as microglia was assessed by immunostaining against the microglia/macrophage markers Iba1, CD11b, CD68, CD45 and TMEM119. Phagocytic function of microglia could be demonstrated by phagocytosis of fluorescence beads and their response to lipopolysaccharide (LPS). As a conclusion, we developed a protocol for isolation and cultivation of pig retinal microglial cells that are suitable for research in the laboratory.

Histone Methylation Inhibitor DZNep Ameliorated the Renal Ischemia-Reperfusion Injury via Inhibiting TIM-1 Mediated T Cell Activation

Renal ischemia-reperfusion injury (IRI) after renal transplantation often leads to the loss of kidney graft function. However, there is still a lack of efficient regimens to prevent or alleviate renal IRI. Our study focused on the renoprotective effect of 3-Deazaneplanocin A (DZNep), which is a histone methylation inhibitor. We found that DZNep significantly alleviated renal IRI by suppressing nuclear factor kappa-B (NF-κB), thus inhibiting the expression of inflammatory factors in renal tubular epithelial cells in vivo or in vitro. After treatment with DZNep, T cell activation was impaired in the spleen and kidney, which correlated with the downregulated expression of T-cell immunoglobulin mucin (TIM)-1 on T cells and TIM-4 in macrophages. In addition, pretreatment with DZNep was not sufficient to protect the kidney, while administration of DZNep from before to after surgery significantly ameliorated IRI. Our findings suggest that DZNep can be a novel strategy for preventing renal IRI following kidney transplantation.

Inhibition of TIM-4 protects against cerebral ischaemia-reperfusion injury

TIM‐4 plays an important role in ischaemia‐reperfusion injury of liver and kidney; however, the effects of TIM‐4 on cerebral ischaemia‐reperfusion injury (IRI) are unknown. The purpose of the present study was to investigate the potential role of TIM‐4 in experimental brain ischaemia‐reperfusion injury. In this study, cerebral ischaemia reperfusion was induced by transient middle cerebral artery occlusion (MCAO) for 1 hour in C57/BL6 mice. The TIM‐4 expression was detected in vivo or vitro by real‐time quantitative polymerase chain reaction, Western blot and flow cytometric analysis. In vivo, the administration of anti‐TIM‐4 antibodies significantly suppressed apoptosis, inhibited inflammatory cells and enhanced anti‐inflammatory responses. In vitro, activated microglia exhibited reduced cellular proliferation and induced IRI injury when co‐cultured with neurons; these effects were inhibited by anti‐TIM‐4 antibody treatment. Similarly, microglia transfected with TIM‐4 siRNA and stimulated by LPS + IFN‐γ alleviated the TIM‐4‐mediated damage to neurons. Collectively, our data indicate that the inhibition of TIM‐4 can improve the inflammatory response and exerts a protective effect in cerebral ischaemia‐reperfusion injury.