Bisdemethoxycurcumin Protects Small Intestine from Lipopolysaccharide-Induced Mitochondrial Dysfunction via Activating Mitochondrial Antioxidant Systems and Mitochondrial Biogenesis in Broiler Chickens

Bisdemethoxycurcumin is one of the three curcuminoids of turmeric and exhibits good antioxidant activity in animal models. This study is aimed at investigating the effect of bisdemethoxycurcumin on small intestinal mitochondrial dysfunction in lipopolysaccharide- (LPS-) treated broilers, especially on the mitochondrial thioredoxin 2 system and mitochondrial biogenesis. A total of 320 broiler chickens were randomly assigned into four experimental diets using a 2 × 2 factorial arrangement with diet (0 and 150 mg/kg bisdemethoxycurcumin supplementation) and stress (saline or LPS challenge) for 20 days. Broilers received a dose of LPS (1 mg/kg body weight) or sterile saline intraperitoneally on days 16, 18, and 20 of the trial. Bisdemethoxycurcumin mitigated the mitochondrial dysfunction of jejunum and ileum induced by LPS, as evident by the reduced reactive oxygen species levels and the increased mitochondrial membrane potential. Bisdemethoxycurcumin partially reversed the decrease in the mitochondrial DNA copy number and the depletion of ATP levels. Bisdemethoxycurcumin activated the mitochondrial antioxidant response, including the prevention of lipid peroxidation, enhancement of manganese superoxide dismutase activity, and the upregulation of the mitochondrial glutaredoxin 5 and thioredoxin 2 system. The enhanced mitochondrial respiratory complex activities in jejunum and ileum were also attributed to bisdemethoxycurcumin treatment. In addition, bisdemethoxycurcumin induced mitochondrial biogenesis via transcriptional regulation of proliferator-activated receptor-gamma coactivator-1alpha pathway. In conclusion, our results demonstrated the potential of bisdemethoxycurcumin to attenuate small intestinal mitochondrial dysfunction, which might be mediated via activating the mitochondrial antioxidant system and mitochondrial biogenesis in LPS-treated broilers.

Mechanisms of Trx2/ASK1-Mediated Mitochondrial Injury in Pemphigus Vulgaris

Objective. Apoptotic events mediated by mitochondrial injury play an important role on the onset of Pemphigus vulgaris (PV). The thioredoxin-2 (Trx2)/apoptosis signal-regulating kinase 1 (ASK1) signaling pathway is considered a key cascade involved on the regulation of mitochondrial injury. Hence, we have investigated the regulatory mechanism of the Trx2/ASK1 signaling in PV-induced mitochondrial injury. Methods. Serum and tissue samples were collected from clinical PV patients to detect the oxidative stress factors, cell apoptosis, and expression of members from Trx2/ASK1 signaling. HaCaT cells were cultured with the serum of PV patients and transfected with Trx2 overexpression or silencing vector. Changes in the levels of reactive oxygen species (ROS), mitochondrial membrane potential (△ψm), and apoptosis were further evaluated. A PV mouse model was established and administered with Trx2-overexpressing plasmid. The effect of ectopic Trx2 expression towards acantholysis in PV mice was observed. Results. A series of cellular and molecular effects, including (i) increased levels of oxidative stress products, (ii) destruction of epithelial cells in the skin tissues, (iii) induction of apoptosis in keratinocytes, (iv) reduction of Trx2 protein levels, and (v) enhanced phosphorylation of ASK1, were detected in PV patients. In vitro experiments confirmed that Trx2 can inhibit ASK1 phosphorylation, alleviate ROS release, decrease △ψm, and lower the apoptotic rate. Injection of Trx2-overexpressing vectors in vivo could also relieve acantholysis and blister formation in PV mice. Conclusion. The Trx2/ASK1 signaling pathway regulates the incidence of PV mediated by mitochondrial injury.

Thioredoxin down-regulation in the cytosol in thioredoxin 2 transgenic mice did not have beneficial effects to extend lifespan in male C57BL/6 mice

Background: This study was conducted to test the effects of thioredoxin (Trx)1 down-regulation in Trx2 transgenic [Tg(TXN2)+/0] mice on lifespan and age-related diseases. Our previous study with Tg(TXN2)+/0 mice showed that mitochondrial Trx overexpression produced minimal life-extending effects with a slightly elevated severity of lymphoma and another study with a limited number of Trx1KO mice showed that there was a slight reduction of neoplastic lesions. Thus, this study was aimed to test if reduced Trx1 expression in combination with elevated Trx2 has beneficial effects on lifespan in mice by attenuating age-related diseases, specifically cancer. Methods: Trx2 hemizygous transgenic and Trx1 heterozygous knockout mice [Tg(TXN2)+/0 x Trx1KO] were generated for survival and cross-sectional pathology experiments. Results: Tg(TXN2)+/0 x Trx1KO mice showed significantly higher (approximately 1.5- to 3-fold) Trx2 levels and significantly less (approximately 50% less) Trx1 levels in all of the tissues we examined compared to wildtype (WT) littermates. Trx1 down-regulation along with Trx2 overexpression did not change the levels of glutathione or other major antioxidant enzymes. Male Tg(TXN2)+/0 x Trx1KO mice demonstrated only a slight extension of lifespan in the early part of life and no significant effects on the later part of life were observed,which was similar to our previous study with Tg(TXN2)+/0 mice. Tg(TXN2)+/0 x Trx1KO mice had similar tumor burden, disease burden, incidence and severity of lymphoma, and severity of glomerulonephritis compared to WT mice at 22-26 months. Conclusions: Our findings suggest that the combined Trx down-regulation in cytosol along with upregulation in mitochondria of Tg(TXN2)+/0 x Trx1KO mice did not provide beneficial effects on aging, i.e., extend the lifespan or reduce age-related pathology compared to WT mice. Keywords: Thioredoxin, transgenic mouse, knockout mouse, aging, cancer

Thioredoxin 2 Negatively Regulates Innate Immunity to RNA Viruses by Disrupting the Assembly of the Virus-Induced Signaling Adaptor Complex

ABSTRACT The virus-induced signaling adaptor (VISA) complex plays a critical role in the innate immune response to RNA viruses. However, the mechanism of VISA complex formation remains unclear. Here, we demonstrate that thioredoxin 2 (TRX2) interacts with VISA at mitochondria both in vivo and in vitro. Knockdown and knockout of TRX2 enhanced the formation of the VISA-associated complex, as well as virus-triggered activation of interferon regulatory factor 3 (IRF3) and transcription of the interferon beta 1 (IFNB1) gene. TRX2 inhibits the formation of VISA aggregates by repressing reactive oxygen species (ROS) production, thereby disrupting the assembly of the VISA complex. Furthermore, our data suggest that the C93 residue of TRX2 is essential for inhibition of VISA aggregation, whereas the C283 residue of VISA is required for VISA aggregation. Collectively, these findings uncover a novel mechanism of TRX2 that negatively regulates VISA complex formation. IMPORTANCE The VISA-associated complex plays pivotal roles in inducing type I interferons (IFNs) and eliciting the innate antiviral response. Many host proteins are identified as VISA-associated-complex proteins, but how VISA complex formation is regulated by host proteins remains enigmatic. We identified the TRX2 protein as an important regulator of VISA complex formation. Knockout of TRX2 increases virus- or poly(I·C)-triggered induction of type I IFNs at the VISA level. Mechanistically, TRX2 inhibits the production of ROS at its C93 site, which impairs VISA aggregates at its C283 site, and subsequently impedes the assembly of the VISA complex. Our findings suggest that TRX2 plays an important role in the regulation of VISA complex assembly.