Translocation of protein kinase C δ contributes to the moderately high glucose-, but not hypoxia-induced proliferation in primary cultured human retinal endothelial cells

Thioredoxin-Interacting Protein Inhibited Vascular Endothelial Cell-Induced HREC Angiogenesis Treatment of Diabetic Retinopathy

Diabetic retinopathy is the most common reason for blindness among employed adults worldwide. Hyperglycemia and the overaccumulation of vascular endothelial growth factor (VEGF) lead to diabetic retinopathy, pathological angiogenesis in diabetic retinopathy, and consequent visual impairment. Expression levels of thioredoxin-interacting protein (TXNIP) substantially increase in retinal endothelial cells in diabetic circumstances. The part of TXNIP in retinal angiogenesis combined with diabetes remains unclear. This study examined the effect of reduced TXNIP expression levels and determined how it affects diabetic retinal angiogenesis. Display of human retinal vascular endothelial cells (HRECs) to moderately high glucose (MHG) encouraged tube formation and cell migration, not cell proliferation. In response to MHG conditions, in HRECs, TXNIP knockdown inhibited the production of reactive oxygen species (ROS), cell migration, tube formation, and the Akt/mTOR activation pathway. In addition, gene silencing of TXNIP decreased the VEGF-triggered angiogenic response in HRECs by preventing activation of both VEGF receptor 2 and the downstream components of the Akt/mTOR pathway signaling. Furthermore, TXNIP knockout mice reduced VEGF-induced or VEGF- and MHG-triggered ex vivo retinal angiogenesis compared to wild-type mice. Finally, our findings revealed that TXNIP knockdown suppressed VEGF- and MHG-triggered angiogenic responses in HRECs and mouse retinas, indicating that TXNIP is a promising therapeutic window against the proliferation of diabetic patients' retinopathy.

CCCH-zinc finger antiviral protein relieves immunosuppression of T cell induced by avian leukosis virus subgroup J via NLP-PKC-δ-NFAT pathway

CCCH-zinc finger antiviral protein (ZAP) can recognize and induce the degradation of mRNAs and proteins of certain viruses, as well as exert its antiviral activity by activating T cell. However, the mechanism of ZAP mediating T cell activation during virus infection remains unclear. Here, we found a potential function of ZAP that relieves immunosuppression of T cell induced by avian leukosis virus subgroup J (ALV-J) via a novel signaling pathway that involves norbin like protein (NLP), protein kinase C delta (PKC-δ) and nuclear factor of activated T cell (NFAT). Specifically, ZAP expression activated T cells by promoting the dephosphorylation and nuclear translocation of NFAT. Furthermore, knockdown of ZAP weakened the reactivity and antiviral response of T cells. Mechanistically, ZAP reduced PKC-δ activity by up-regulating and reactivating NLP through competitively binding with viral protein. Knockdown of NLP decreased the dephosphorylation of PKC-δ by ZAP expression. Moreover, we showed that knockdown of PKC-δ reduced the phosphorylation levels of NFAT and enhanced its nuclear translocation. Taken together, these data revealed that ZAP relieves immunosuppression caused by ALV-J and mediates T cell activation through NLP-PKC-δ-NFAT pathway. Importance The evolution of host defense system is driven synchronously in the process of resisting virus invasion. Accordingly, host innate defense factors exert effectively work in suppressing virus replication. However, it remains unclear that whether the host innate defense factors are involved in antiviral immune response against the invasion of immunosuppressive viruses. Here, we found that CCCH-type zinc finger antiviral protein (ZAP) effectively worked in resistance on immunosuppression caused by avian leukosis virus subgroup J (ALV-J), a classic immunosuppressive virus. Evidence showed that ZAP released the phosphatase activity of NLP inhibited by ALV-J and further activated NFAT by inactivating PKC-δ. This novel molecular mechanism that ZAP regulates antiviral immune response by mediating NLP-PKC-δ-NFAT pathway has greatly enriched the understanding of the functions of host innate defense factors and provided important scientific ideas and theoretical basis for the research of immunosuppressive virus and antiviral immunity.

Oxidative Stress as the Main Target in Diabetic Retinopathy Pathophysiology

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus (DM) causing vision impairment even at young ages. There are numerous mechanisms involved in its development such as inflammation and cellular degeneration leading to endothelial and neural damage. These mechanisms are interlinked thus worsening the diabetic retinopathy outcome. In this review, we propose oxidative stress as the focus point of this complication onset.

Thioredoxin-interacting protein deficiency ameliorates diabetic retinal angiogenesis

Diabetic retinopathy is the leading cause of blindness among working-aged adults around the world. Hyperglycemia and intraocular vascular endothelial growth factor (VEGF) over-accumulation are essential for the progression of diabetic retinopathy, which eventually results in proliferative diabetic retinopathy, characterized by pathologic angiogenesis and impaired vision. Thioredoxin-interacting protein (TXNIP) was highly induced in retinal endothelial cells under diabetic conditions. However, the role of TXNIP in diabetes-associated retinal angiogenesis remains elusive. Here, we investigated whether the absence of TXNIP alters diabetes-associated retinal angiogenesis. Exposure of human retinal microvascular endothelial cells (HRMECs) to moderately high glucose (MHG) promoted cell migration and tube formation, but not proliferation. Knockdown of TXNIP suppressed moderately high glucose (MHG)-induced reactive oxygen species (ROS) generation, migration, tube formation and activation of Akt/mTOR pathway in HRMECs. Moreover, gene silencing of TXNIP inhibited VEGF-induced angiogenic response by blocking VEGFR2 and downstream signal pathway Akt/mTOR activation in HRMECs. Furthermore, TXNIP knockout inhibited VEGF or VEGF and MHG-induced retinal angiogenesis ex vivo compared with wild-type mice. In conclusion, our study demonstrated that TXNIP deficiency inhibited VEGF or/and MHG-induced angiogenic response in HRMECs and mice retinas and suggested TXNIP may be a potential therapy target for treating proliferative diabetic retinopathy.