Betulinic acid attenuates lipopolysaccharide-induced vascular hyporeactivity in the rat aorta by modulating Nrf2 antioxidative function.

Betulinic acid (BA), a pentacyclic triterpenoid, has been reported to inhibit cardiovascular dysfunction under sepsis-induced oxidative stress. Nuclear factor erythroid-2 related factor-2 (Nrf2) is regarded as a key transcription factor regulating expression of endogenous antioxidative genes. To explore the preventive effects of BA against vascular hyporeactivity and the related antioxidative mechanism in sepsis, contraction and relaxation in aortas isolated from lipopolysaccharide (LPS)-challenged rats were performed. Male Sprague-Dawley rats were pretreated with brusatol (Bru, 0.4 mg/kg/2 days, i.p.), an inhibitor of Nrf2, and BA (10, 25, 50 mg/kg/day, i.g.) for 3 days and injected with LPS (10 mg/kg, i.p.) at the 4th day. Rats were anesthetized and killed by cervical dislocation after they were treated with LPS for 4 h. Thoracic aortas were immediately dissected out to determine contraction and relaxation using the organ bath system. Pro-inflammatory factors interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) and oxidative stress were measured in aortic tissues and plasma. mRNA expression of Nrf2-regulated antioxidative enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GPx), and heme oxygenase-1 (HO-1), in rat aortas was determined. Increases of IL-1ß, TNF-α, nitric oxide, and malondialdehyde and the decrease of glutathione induced by LPS were significantly attenuated by pretreatment with different doses of BA in plasma and aortas (p < 0.05 versus LPS), all of which were blocked by Bru (p < 0.01). Inhibition of phenylephrine (PE)- and KCl-induced contractions and acetylcholine (ACh)-induced vasodilatation in aortas from LPS-challenged rats was dose-dependently reduced by BA (p < 0.05; percentage improvements by BA in PE-induced contraction were 55.38%, 96.41%, and 104.33%; those in KCl-induced contraction were 15.11%, 23.96%, and 22.96%; and those in ACh-induced vasodilatation were 16.08%, 42.99%, and 47.97%), all of which were reversed by Bru (p < 0.01). Improvements of SOD, GPx, and HO-1 mRNA expression conferred by BA in LPS-challenged rat aortas were inhibited by Bru (p < 0.01; 145.45% versus 17.42%, 160.69% versus 22.76%, and 166.88% versus 23.57%). These findings suggest that BA attenuates impairments of aortic contraction and relaxation in LPS-challenged rats by activating Nrf2-regulated antioxidative pathways.

Prognostic Role of Mitochondrial Transcription Termination Factor 3 in Thyroid Carcinoma.

Background: Studies have shown that the Mitochondrial Transcription Termination Factor 3 (MTERF3) negatively regulates mitochondrial gene expression and energy metabolism, and plays a significant role in many cancer types. Nevertheless, the expression and prognostic role of MTERF3 in patients with thyroid carcinoma (THCA) is still unclear. Thus, we investigated the expression, clinicopathological significance, and prognostic value of MTERF3 in THCA. Methods: The protein and mRNA expression levels of MTERF3 were, respectively, analyzed using immunohistochemistry (IHC) from THCA tissues and RNA-Seq data downloaded from The Cancer Genome Atlas. In addition, the relationships among the expression of MTERF3, the stemness feature, the extent of immune infiltration, drug sensitivity, the expression of ferroptosis, and N6-methyladenosine (m6A) methylation regulators, were evaluated as prognostic indicators for patients with THCA using the Kaplan-Meier plotter database. Results: The IHC and RNAseq results showed that the protein and mRNA expression levels of MTERF3 in adjacent nontumor tissues were significantly higher than in THCA tissues. The survival analysis indicated that decreased expression of MTERF3 was associated with a poorer prognosis. Furthermore, the expression of MTERF3 not only negatively correlated with the enhancement of the stemness of THCA and the reduction of drug sensitivity but also was implicated in ferroptosis and m6A methylation. Conclusion: The data from this study support the hypothesis that decreased expression of MTERF3 in THCA is associated with a poor prognosis.

Sestrin2 is involved in the Nrf2-regulated antioxidative signaling pathway in luteolin-induced prevention of the diabetic rat heart from ischemia/reperfusion injury.

Luteolin attenuates myocardial ischemia/reperfusion (I/R) injury in diabetes through activating the nuclear factor erythroid 2-related factor 2 (Nrf2)-related antioxidative response. Though sestrin2, a highly conserved stress-inducible protein, is regarded as a modulator of Nrf2 and reduces I/R injury, the effect of sestrin2 on luteolin-induced prevention of the diabetic heart from I/R injury remains unclear. We hypothesized that luteolin could relieve myocardial I/R injury in diabetes by activating the sestrin2-modulated Nrf2 antioxidative response. Diabetes was induced in rats using a single dose of streptozotocin (65 mg kg-1, i.p.) for 6 weeks, and then luteolin (100 mg kg-1 d-1, i.g.), Nrf2 inhibitor brusatol, or sestrin2 blocker leucine was administered for 2 consecutive weeks. After that, the hearts were isolated and exposed to global I/R (30 min/120 min). Luteolin markedly improved cardiac function, myocardial viability and expressions of Nrf2-regulated antioxidative genes, and reduced lactate dehydrogenase release, malondialdehyde, and 8-hydroxydeoxyguanosine in the diabetic I/R hearts. Ca2+-induced mitochondrial permeability transition and membrane potential disruption were markedly inhibited in luteolin-treated diabetic ventricular myocytes. All these effects of luteolin were significantly reversed by Nrf2 inhibitor brusatol or sestrin2 inhibitor leucine. Luteolin-induced diminished Keap1 and augmented nuclear translocation and ARE binding activity of Nrf2 were hampered by leucine in the diabetic I/R heart. In addition, luteolin-induced augmented transcription of sestrin2 was markedly blocked by brusatol in the diabetic I/R heart. These data suggest that sestrin2 and Nrf2 positively interact to promote antioxidative actions and attenuate mitochondrial damage, by which luteolin relieves diabetic myocardial I/R injury.

Luteolin Attenuates Cardiac Ischemia/Reperfusion Injury in Diabetic Rats by Modulating Nrf2 Antioxidative Function.

Luteolin has been reported to attenuate ischemia/reperfusion (I/R) injury in the diabetic heart through endothelial nitric oxide synthase- (eNOS-) related antioxidative response. Though the nuclear factor erythroid 2-related factor 2 (Nrf2) is regarded as a key endogenous factor to reduce diabetic oxidative stress, whether luteolin reduces cardiac I/R injury in the diabetic heart via enhancing Nrf2 function needs to be clarified. We hypothesized that pretreatment with luteolin could alleviate cardiac I/R injury in the diabetic heart by affecting the eNOS/Nrf2 signaling pathway. The diabetic rat was produced by a single injection of streptozotocin (65 mg/kg, i.p.) for 6 weeks, and then, luteolin (100 mg/kg/day, i.g.), eNOS inhibitor L-NAME, or Nrf2 inhibitor brusatol was administered for the succedent 2 weeks. After that, the isolated rat heart was exposed to 30 min of global ischemia and 120 min of reperfusion to establish I/R injury. Luteolin markedly ameliorated cardiac function and myocardial viability; upregulated expressions of heme oxygenase-1, superoxide dismutase, glutathione peroxidase, and catalase; and reduced myocardial lactate dehydrogenase release, malondialdehyde, and 8-hydroxydeoxyguanosine in the diabetic I/R heart. All these ameliorating effects of luteolin were significantly reversed by L-NAME or brusatol. Luteolin also markedly reduced S-nitrosylation of Kelch-like ECH-associated protein 1 (Keap1) and upregulated Nrf2 and its transcriptional activity. This effect of luteolin on Keap1/Nrf2 signaling was attenuated by L-NAME. These data reveal that luteolin protects the diabetic heart against I/R injury by enhancing eNOS-mediated S-nitrosylation of Keap1, with subsequent upregulation of Nrf2 and the Nrf2-related antioxidative signaling pathway.

Luteolin alleviates cardiac ischemia/reperfusion injury in the hypercholesterolemic rat via activating Akt/Nrf2 signaling.

Myocardial ischemia/reperfusion (I/R) injury in hypercholesterolemia is associated with oxidative stress, while luteolin is known to reduce oxidative stress by activating Akt/nuclear factor erythroid-2-related factor 2 (Nrf2) signaling and alleviate cardiac I/R injury. Here, we investigated whether luteolin pretreatment diminishes myocardial I/R injury in hypercholesterolemic rats by activating Akt/Nrf2 signaling. Hypercholesterolemic rats were produced by 2% cholesterol diet for 8 weeks. Luteolin (100 mg/kg/day, i.g.) or LY294002 was administered for the last 2 weeks. The hearts were then isolated and subjected to 30 min of global ischemia followed by 120 min of reperfusion. Pretreatment with luteolin significantly improved left ventricular function throughout reperfusion, increased cardiac tissue viability, reduced coronary lactate dehydrogenase release and the myocardial malondialdehyde level, upregulated p-Akt and p-GSK3ß expressions, inhibited nuclear translocation of Fyn, and activated Nrf2 function in hypercholesterolemic I/R rat hearts. All these improving effects of luteolin were significantly attenuated by LY294002. Ca2+-induced mitochondrial permeability transition pore (mPTP) opening and mitochondrial inner membrane potential reduction were significantly inhibited in ventricular myocytes isolated from luteolin-treated hypercholesterolemic rats, which were attenuated by LY294002. These results indicate that luteolin protects the hypercholesterolemic heart against I/R injury due to upregulation of Akt-mediated Nrf2 antioxidative function and inhibition of mPTP.