Improving lysosomal ferroptosis with NMN administration protects against heart failure.

Myocardial mitochondria are primary sites of myocardial energy metabolism. Mitochondrial disorders are associated with various cardiac diseases. We previously showed that mice with cardiomyocyte-specific knockout of the mitochondrial translation factor p32 developed heart failure from dilated cardiomyopathy. Mitochondrial translation defects cause not only mitochondrial dysfunction but also decreased nicotinamide adenine dinucleotide (NAD+) levels, leading to impaired lysosomal acidification and autophagy. In this study, we investigated whether nicotinamide mononucleotide (NMN) administration, which compensates for decreased NAD+ levels, improves heart failure because of mitochondrial dysfunction. NMN administration reduced damaged lysosomes and improved autophagy, thereby reducing heart failure and extending the lifespan in p32cKO mice. We found that lysosomal damage due to mitochondrial dysfunction induced ferroptosis, involving the accumulation of iron in lysosomes and lipid peroxide. The ameliorative effects of NMN supplementation were found to strongly affect lysosomal function rather than mitochondrial function, particularly lysosome-mediated ferroptosis. NMN supplementation can improve lysosomal, rather than mitochondrial, function and prevent chronic heart failure.

Equol inhibits prostate cancer growth through degradation of androgen receptor by S-phase kinase-associated protein 2.

Chemopreventive and potential therapeutic effects of soy isoflavones have been shown to be effective in numerous preclinical studies as well as clinical studies in prostate cancer. Although the inhibition of androgen receptor signaling has been supposed as one mechanism underlying their effects, the precise mechanism of androgen receptor inhibition remains unclear. Thus, this study aimed to clarify their mechanism. Among soy isoflavones, equol suppressed androgen receptor as well as prostate-specific antigen expression most potently in androgen-dependent LNCaP cells. However, the inhibitory effect on androgen receptor expression and activity was less prominent in castration-resistant CxR and 22Rv1 cells. Consistently, cell proliferation was suppressed and cellular apoptosis was induced by equol in LNCaP cells, but less so in CxR and 22Rv1 cells. We revealed that the proteasome pathway through S-phase kinase-associated protein 2 (Skp2) was responsible for androgen receptor suppression. Taken together, soy isoflavones, especially equol, appear to be promising as chemopreventive and therapeutic agents for prostate cancer based on the fact that equol augments Skp2-mediated androgen receptor degradation. Moreover, because Skp2 expression was indicated to be crucial for the effect of soy isoflavones, soy isoflavones may be applicable for precancerous and cancerous prostates.

Sensitivity of doxorubicin-resistant cells to sorafenib: possible role for inhibition of eukaryotic initiation factor-2alpha phosphorylation.

Patients with advanced cancer including breast cancer, hepatocellular cancer and urothelial cancer frequently receive a chemotherapy regimen containing doxorubicin. However, doxorubicin-resistance is a major obstacle for cancer chemotherapy. Recently, several molecular-targeted agents have become available. Sorafenib (BAY 43-9006) is known to target multiple kinases and has demonstrated activity in renal cell and hepatocellular cancer. In this study, sorafenib was found to inhibit phosphorylation of the eukaryotic initiation factor-2alpha (eIF2alpha), induce cell cycle arrest at G2 phase and increase cellular apoptosis in doxorubicin-resistant human urothelial cell lines. An eIF2alpha kinase, PERK was responsible for eIF2alpha phosphorylation and PERK knockdown induced cellular apoptosis similar to sorafenib treatment in doxorubicin-resistant cancer cells. Furthermore, sorafenib sensitized doxorubicin-resistant cancer cells, but not their parental cells to oxidative stress exerted by both hydrogen peroxide and doxorubicin. In addition, PERK knockdown sensitized doxorubicin-resistant cancer cells to oxidative stress. In conclusion, PERK inhibition using sorafenib with or without doxorubicin might be a promising therapeutic approach for doxorubicin-resistant cancers retaining high phosphorylation levels of eIF2alpha.

[Cisplatin sensitivity transcriptional factor and mitochondrial DNA maintenance protein].

Cisplatin is one of the most commonly used chemotherapeutic agents, with demonstrated activity against a diverse spectrum of malignancies, including testicular cancer, ovarian carcinoma, and head/neck tumors. However, the therapeutic efficacy of the drug is limited by the severity of its side effects and the potential progression of tumor cells to a cisplatin-resistant state. We found that the transcription factors of genes involved in cisplatin resistance are often overexpressed or activated in cisplatin-resistant cells. In this paper, we describe ATF4, Clock, ZNF143, and YB-1 as cisplatin resistance genes. Clock and the ATF4 transcription system might play an important role in multidrug resistance through the glutathione-dependent redox system, and the physiological potential of the Clock-controlled redox system might be important to better understand oxidative stress-associated disorders including cancer and systemic chronotherapy. We also describe the basis for understanding the effects of cisplatin on mitochondrial activity and the mechanisms of cellular toxicity and resistance caused by this drug.

Effects of grapefruit juice and orange juice components on P-glycoprotein- and MRP2-mediated drug efflux.

We investigated the effects of grapefruit juice (GFJ) and orange juice (OJ) on drug transport by MDR1 P-glycoprotein (P-gp) and multidrug resistance protein 2 (MRP2), which are efflux transporters expressed in human small intestine. We examined the transcellular transport and uptake of [(3)H]vinblastine (VBL) and [(14)C]saquinavir in a human colon carcinoma cell line (Caco-2) and in porcine kidney epithelial cell lines transfected with human MDR1 cDNA and human MRP2 cDNA, LLC-GA5-COL150, and LLC-MRP2, respectively. In Caco-2 cells, the basal-to-apical transports of [(3)H]VBL and [(14)C]saquinavir were greater than those in the opposite direction. The ratio of basal-to-apical transport to apical-to-basal transport of [(3)H]VBL and [(14)C]saquinavir by Caco-2 cells was reduced in the presence of MK571 (MRPs inhibitor), verapamil (P-gp inhibitor), cyclosporin A (inhibitor of both), 50% ethyl acetate extracts of GFJ and OJ, or their components (6',7'-dihydroxybergamottin, bergamottin, tangeretin, hepatomethoxyflavone, and nobiletin). Studies of transport and uptake of [(3)H]VBL and [(14)C]saquinavir with MDR1 and MRP2 transfectants showed that VBL and saquinavir are transported by both P-gp and MRP2. GFJ and OJ components inhibited the transport by MRP2 as well as P-gp. However, their inhibitory potencies for P-gp or MRP2 were substrate-dependent. The present study has revealed that GFJ and OJ interact with not only P-gp but also MRP2, both of which are expressed at apical membranes and limit the apical-to-basal transport of VBL and saquinavir in Caco-2 cells.