Protein transduction domain-hA20 fusion protein protects endothelial cells against high glucose-induced injury

Transduced Tat-DJ-1 protein inhibits cytokines-induced pancreatic RINm5F cell death

Loss of pancreatic β-cells by oxidative stress or cytokines is associated with diabetes mellitus (DM). DJ-1 is known to as a multifunctional protein, which plays an important role in cell survival. We prepared cell permeable wild type (WT) and mutant type (M26I) Tat-DJ-1 proteins to investigate the effects of DJ-1 against combined cytokines (IL-1β, IFN-γ and TNF-α)-induced RINm5F cell death. Both Tat-DJ-1 proteins were transduced into RINm5F cells. WT Tat-DJ-1 proteins significantly protected against cell death from cytokines by reducing intracellular toxicities. Also, WT Tat-DJ-1 proteins markedly regulated cytokines-induced pro- and anti-apoptosis proteins. However, M26I Tat-DJ-1 protein showed relatively low protective effects, as compared to WT Tat-DJ-1 protein. Our experiments demonstrated that WT Tat-DJ-1 protein protects against cytokine-induced RINm5F cell death by suppressing intracellular toxicities and regulating apoptosisrelated protein expression. Thus, WT Tat-DJ-1 protein could potentially serve as a therapeutic agent for DM and cytokine related diseases. [BMB Reports 2016; 49(5): 297-302]

Role of A20 in cIAP-2 protection against tumor necrosis factor α (TNF-α)-mediated apoptosis in endothelial cells

Tumor necrosis factor α (TNF-α) influences endothelial cell viability by altering the regulatory molecules involved in induction or suppression of apoptosis. However, the underlying mechanisms are still not completely understood. In this study, we demonstrated that A20 (also known as TNFAIP3, tumor necrosis factor α-induced protein 3, and an anti-apoptotic protein) regulates the inhibitor of apoptosis protein-2 (cIAP-2) expression upon TNF-α induction in endothelial cells. Inhibition of A20 expression by its siRNA resulted in attenuating expression of TNF-α-induced cIAP-2, yet not cIAP-1 or XIAP. A20-induced cIAP-2 expression can be blocked by the inhibition of phosphatidyl inositol-3 kinase (PI3-K), but not nuclear factor (NF)-κB, while concomitantly increasing the number of endothelial apoptotic cells and caspase 3 activation. Moreover, TNF-α-mediated induction of apoptosis was enhanced by A20 inhibition, which could be rescued by cIAP-2. Taken together, these results identify A20 as a cytoprotective factor involved in cIAP-2 inhibitory pathway of TNF-α-induced apoptosis. This is consistent with the idea that endothelial cell viability is dependent on interactions between inducers and suppressors of apoptosis, susceptible to modulation by TNF-α.

HIV-TAT mediated protein transduction of Cu/Zn-superoxide dismutase-1 (SOD1) protects skin cells from ionizing radiation

Background

Radiation-induced skin injury remains a serious concern during radiotherapy. Cu/Zn-superoxide dismutase (Cu/Zn-SOD, SOD₁) is a conserved enzyme for scavenging superoxide radical in cells. Because of the integrity of cell membranes, exogenous molecule is not able to be incorporated into cells, which limited the application of natural SOD₁. The aim of this study was to evaluate the protective role of HIV-TAT protein transduction domain mediated protein transduction of SOD₁ (TAT-SOD₁) against ionizing radiation.

Methods

The recombinant TAT-SOD₁ and SOD₁ were obtained by prokaryotic–based protein expression system. The transduction effect and biological activity of TAT-SOD₁ was measured by immunofluorescence and antioxidant capability assays in human keratinocyte HaCaT cells. Mito-Tracker staining, reactive oxygen species (ROS) generation assay, cell apoptosis analysis and malondialdehyde (MDA) assay were used to access the protective effect of TAT- SOD₁.

Results

Uptake of TAT-SOD₁ by HaCaT cells retained its biological activity. Compared with natural SOD₁, the application of TAT-SOD₁ significantly enhanced the viability and decreased the apoptosis induced by X-ray irradiation. Moreover, TAT-SOD₁ reduced ROS and preserved mitochondrial integrity after radiation exposure in HaCaT cells. Radiation-induced γH2AX foci, which are representative of DNA double strand breaks, were decreased by pretreatment with TAT-SOD₁. Furthermore, subcutaneous application of TAT-SOD₁ resulted in a significant decrease in 45 Gy electron beam-induced ROS and MDA concentration in the skins of rats.

Conclusions

This study provides evidences for the protective role of TAT-SOD₁ in alleviating radiation-induced damage in HaCaT cells and rat skins, which suggests a new therapeutic strategy for radiation-induced skin injury.