Age alters the oncogenic trajectory toward luminal mammary tumors that activate unfolded proteins responses.

A major limitation in the use of mouse models in breast cancer research is that most mice develop estrogen receptor-alpha (ERα)-negative mammary tumors, while in humans, the majority of breast cancers are ERα-positive. Therefore, developing mouse models that best mimic the disease in humans is of fundamental need. Here, using an inducible MMTV-rtTA/TetO-NeuNT mouse model, we show that despite being driven by the same oncogene, mammary tumors in young mice are ERα-negative, while they are ERα-positive in aged mice. To further elucidate the mechanisms for this observation, we performed RNAseq analysis and identified genes that are uniquely expressed in aged female-derived mammary tumors. We found these genes to be involved in the activation of the ERα axis of the mitochondrial UPR and the ERα-mediated regulation of XBP-1s, a gene involved in the endoplasmic reticulum UPR. Collectively, our results indicate that aging alters the oncogenic trajectory towards the ERα-positive subtype of breast cancers, and that mammary tumors in aged mice are characterized by the upregulation of multiple UPR stress responses regulated by the ERα.

Can THEM6 targeting stop resistance to prostate cancer treatment?

Prostate cancer (PCa) clinical management relies heavily on androgen-deprivation therapy (ADT). However, despite experiencing initial clinical benefit, patients getting ADT for non-resectable PCa eventually relapse and develop fatal castration-resistant PCa (CRPC). Multiple mechanisms of acquired resistance to treatment have been reported, including metabolic adaptation (Marine et al, 2020). Notably, activation of the endoplasmic reticulum (ER) unfolded protein response (UPR) has been associated with oncogenic transformation (Hart et al, 2012), tumor progression, metastasis dissemination, and resistance to therapy (Chen & Cubillos-Ruiz, 2021). Targeting different branches of ER UPR has been found to be an effective tool against aggressive PCa (Nguyen et al, 2018; Sheng et al, 2019). Therefore, a better understanding of these pathways may lead to the identification of novel drug targets.

The portrait of liver cancer is shaped by mitochondrial genetics.

Cancer heterogeneity and evolution are not fully understood. Here, we show that mitochondrial DNA of the normal liver shapes tumor progression, histology, and immune environment prior to the acquisition of oncogenic mutation. Using conplastic mice, we show that mtDNA dictates the expression of the mitochondrial unfolded protein response (UPRmt) in the normal liver. Activation of oncogenic mutations in UPRmt-positive liver increases tumor incidence and histological heterogeneity. Further, in a subset of UPRmt-positive mice, invasive liver cancers develop. RNA sequencing (RNA-seq) analysis of the normal liver reveals that, in this subset, the PAPP-A/DDR2/SNAIL axis of invasion pre-exists along with elevated collagen. Since PAPP-A promotes immune evasion, we analyzed the immune signature and found that their livers are immunosuppressed. Further, the PAPP-A signature identifies the immune exhausted subset of hepatocellular carcinoma (HCC) in humans. Our data suggest that mtDNA of normal liver shapes the entire liver cancer portrait upon acquisition of oncogenic mutations.

Are the estrogen receptor and SIRT3 axes of the mitochondrial UPR key regulators of breast cancer sub-type determination according to age?

Aging is a major risk factor of developing breast cancer. Despite the fact that post-menopausal women have lower levels of estrogen, older women have a higher rate of estrogen receptor alpha (ERα) positive breast cancer. Conversely, young women who have elevated levels of estrogen tend to develop ERα negative disease that is associated with higher rate of metastasis. This perspective proposes a unifying model centered around the importance of mitochondrial biology in cancer and aging to explain these observations. Mitochondria are essential for the survival of cancer cells and therefore pathways that maintain the functionality of the mitochondrial network in cancer cells fulfill a critical role in the survival of cancer cells. The ERα and the mitochondrial sirtuin-3 (SIRT3) have been reported to be key players of the mitochondrial unfolded protein response (UPRmt) 1-5. The UPRmt is a complex retrograde signaling cascade that regulates the communication between the mitochondria and the nucleus to restore mitochondrial fitness in response to oxidative stress 5-7. SIRT3 is a major regulator of aging 8. Its level decreases with age and single nucleotide polymorphisms (SNPs) that preserve its expression at higher levels are observed in centenarians 9,10. We propose a model whereby the ERα axis of the UPRmt acts to compensate for the loss of SIRT3 observed with age, and becomes the dominant axis of the UPRmt to maintain the integrity of the mitochondria during transformation, thus explaining the selective advantage of ERα positive luminal cells in breast cancer arising from older women.

Folding Mitochondrial-Mediated Cytosolic Proteostasis Into the Mitochondrial Unfolded Protein Response.

Several studies reported that mitochondrial stress induces cytosolic proteostasis. How mitochondrial stress activates proteostasis in the cytosol remains unclear. However, the cross-talk between the mitochondria and cytosolic proteostasis has far reaching implications for treatment of proteopathies including neurodegenerative diseases. This possibility appears within reach since selected drugs have begun to emerge as being able to stimulate mitochondrial-mediated cytosolic proteostasis. In this review, we focus on studies describing how mitochondrial stress activates proteostasis in the cytosol across multiple model organisms. A model is proposed linking mitochondrial-mediated regulation of cytosolic translation, folding capacity, ubiquitination, and proteasome degradation and autophagy as a multi layered control of cytosolic proteostasis that overlaps with the integrated stress response (ISR) and the mitochondrial unfolded protein response (UPRmt). By analogy to the conductor in an orchestra managing multiple instrumental sections into a dynamically integrated musical piece, the cross-talk between these signaling cascades places the mitochondria as a major conductor of cellular integrity.

Mitochondrially targeted cytochrome P450 2D6 is involved in monomethylamine-induced neuronal damage in mouse models.

Parkinson's disease (PD) is a major human disease associated with degeneration of the central nervous system. Evidence suggests that several endogenously formed 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-mimicking chemicals that are metabolic conversion products, especially ß-carbolines and isoquinolines, act as neurotoxins that induce PD or enhance progression of the disease. We have demonstrated previously that mitochondrially targeted human cytochrome P450 2D6 (CYP2D6), supported by mitochondrial adrenodoxin and adrenodoxin reductase, can efficiently catalyze the conversion of MPTP to the toxic 1-methyl-4-phenylpyridinium ion. In this study, we show that the mitochondrially targeted CYP2D6 can efficiently catalyze MPTP-mimicking compounds, i.e. 2-methyl-1,2,3,4-tetrahydroisoquinoline, 2-methyl-1,2,3,4-tetrahydro-ß-carboline, and 9-methyl-norharmon, suspected to induce PD in humans. Our results reveal that activity and respiration in mouse brain mitochondrial complex I are significantly affected by these toxins in WT mice but remain unchanged in Cyp2d6 locus knockout mice, indicating a possible role of CYP2D6 in the metabolism of these compounds both in vivo and in vitro These metabolic effects were minimized in the presence of two CYP2D6 inhibitors, quinidine and ajmalicine. Neuro-2a cells stably expressing predominantly mitochondrially targeted CYP2D6 were more sensitive to toxin-mediated respiratory dysfunction and complex I inhibition than cells expressing predominantly endoplasmic reticulum-targeted CYP2D6. Exposure to these toxins also induced the autophagic marker Parkin and the mitochondrial fission marker Dynamin-related protein 1 (Drp1) in differentiated neurons expressing mitochondrial CYP2D6. Our results show that monomethylamines are converted to their toxic cationic form by mitochondrially directed CYP2D6 and result in neuronal degradation in mice.

Cigarette Smoke Toxins-Induced Mitochondrial Dysfunction and Pancreatitis Involves Aryl Hydrocarbon Receptor Mediated Cyp1 Gene Expression: Protective Effects of Resveratrol.

We previously reported that mitochondrial CYP1 enzymes participate in the metabolism of polycyclic aromatic hydrocarbons and other carcinogens leading to mitochondrial dysfunction. In this study, using Cyp1b1-/-, Cyp1a1/1a2-/-, and Cyp1a1/1a2/1b1-/- mice, we observed that cigarette and environmental toxins, namely benzo[a]pyrene (BaP) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), induce pancreatic mitochondrial respiratory dysfunction and pancreatitis. Our results suggest that aryl hydrocarbon receptor (AhR) activation and resultant mitochondrial dysfunction are associated with pancreatic pathology. BaP treatment markedly inhibits pancreatic mitochondrial oxygen consumption rate (OCR), ADP-dependent OCR, and also maximal respiration, in wild-type mice but not in Cyp1a1/1a2-/- and Cyp1a1/1a2/1b1-/- mice. In addition, both BaP and TCDD treatment markedly affected mitochondrial complex IV activity, in addition to causing marked reduction in mitochondrial DNA content. Interestingly, the AhR antagonist resveratrol, attenuated BaP-induced mitochondrial respiratory defects in the pancreas, and reversed pancreatitis, both histologically and biochemically in wild-type mice. These results reveal a novel role for AhR- and AhR-regulated CYP1 enzymes in eliciting mitochondrial dysfunction and cigarette toxin-mediated pancreatic pathology. We propose that increased mitochondrial respiratory dysfunction and oxidative stress are involved in polycyclic aromatic hydrocarbon associated pancreatitis. Resveratrol, a chemo preventive agent and AhR antagonist, and CH-223191, a potent and specific AhR inhibitor, confer protection against BaP-induced mitochondrial dysfunction and pancreatic pathology.

Impairment of energy sensors, SIRT1 and AMPK, in lipid induced inflamed adipocyte is regulated by Fetuin A.

Although several reports demonstrated that accumulation of excess lipid in adipose tissue produces defects in adipocyte which leads to the disruption of energy homeostasis causing severe metabolic problems, underlying mechanism of this event remains yet unclear. Here we demonstrate that FetuinA (FetA) plays a critical role in the impairment of two metabolic sensors, SIRT1 and AMPK, in inflamed adipocytes of high fat diet (HFD) mice. A linear increase in adipocyte hypertrophy from 10 to 16 week was in tandem with the increase in FetA and that coincided with SIRT1 cleavage and decrease in pAMPK which adversely affects PGC1α activation. Knock down (KD) of FetA gene in HFD mice could significantly improve this situation indicating FetA's contribution in the damage of energy sensors in inflamed adipocyte. However, FetA effect was not direct, it was mediated through TNF-α which again is dependent on FetA as FetA augments TNF-α expression. FetA being an upstream regulator of TNF-α, its suppression prevented TNF-α mediated Caspase-1 activation and cleavage of SIRT1. FetA induced inactivation of PGC1α due to SIRT1 cleavage decreased PPARϒ, adiponectin, NRF1 and Tfam expression. All these together caused a significant fall in mitochondrial biogenesis and bioenergetics that disrupted energy homeostasis resulting loss of insulin sensitivity. Taken together, our findings revealed a new dimension of FetA, it not only induced inflammation in adipocyte but also acts as an upstream regulator of SIRT1 cleavage and AMPK activation. Intervention of FetA may be worthwhile to prevent metabolic imbalance that causes insulin resistance and type 2 diabetes.

A Small Insulinomimetic Molecule Also Improves Insulin Sensitivity in Diabetic Mice.

Dramatic increase of diabetes over the globe is in tandem with the increase in insulin requirement. This is because destruction and dysfunction of pancreatic ß-cells are of common occurrence in both Type1 diabetes and Type2 diabetes, and insulin injection becomes a compulsion. Because of several problems associated with insulin injection, orally active insulin mimetic compounds would be ideal substitute. Here we report a small molecule, a peroxyvanadate compound i.e. DmpzH[VO(O2)2(dmpz)], henceforth referred as dmp, which specifically binds to insulin receptor with considerable affinity (KD-1.17µM) thus activating insulin receptor tyrosine kinase and its downstream signaling molecules resulting increased uptake of [14C] 2 Deoxy-glucose. Oral administration of dmp to streptozotocin treated BALB/c mice lowers blood glucose level and markedly stimulates glucose and fatty acid uptake by skeletal muscle and adipose tissue respectively. In db/db mice, it greatly improves insulin sensitivity through excess expression of PPARγ and its target genes i.e. adiponectin, CD36 and aP2. Study on the underlying mechanism demonstrated that excess expression of Wnt3a decreased PPARγ whereas dmp suppression of Wnt3a gene increased PPARγ expression which subsequently augmented adiponectin. Increased production of adiponectin in db/db mice due to dmp effected lowering of circulatory TG and FFA levels, activates AMPK in skeletal muscle and this stimulates mitochondrial biogenesis and bioenergetics. Decrease of lipid load along with increased mitochondrial activity greatly improves energy homeostasis which has been found to be correlated with the increased insulin sensitivity. The results obtained with dmp, therefore, strongly indicate that dmp could be a potential candidate for insulin replacement therapy.

Fetuin-A downregulates adiponectin through Wnt-PPARγ pathway in lipid induced inflamed adipocyte.

Adiponectin secreted from adipocytes is an anti-diabetic and anti-atherogenic adipokine. Adiponectin level is known to fall significantly in obesity induced type 2 diabetes which worsen insulin sensitivity because of aberrant lipid management. However, underlying mechanism of adiponectin decrease in obese diabetic condition is yet unclear. We report here that lowering of plasma adiponectin coincided with the higher Fetuin A (FetA) level in high fat diet (HFD) induced obese diabetic mice. Knock down of FetA gene (FetAKD) elevated adiponectin level markedly in HFD mice, while reinforcement of FetA into FetAKDHFD mice reduced its level again. These results indicate FetA's involvement in the lowering of adiponectin level in obesity induced diabetic mice. Our findings to understand how FetA could affect adiponectin decrease demonstrated that FetA could enhance Wnt3a expression in the adipocyte of HFD mice. FetA addition to 3T3L1 adipocyte incubation elevated Wnt3a expression in a dose dependent manner. Overexpression of Wnt3a by FetA inhibited PPARγ and adiponectin. FetA failed to reduce PPARγ and adiponectin in Wnt3a gene knocked down 3T3L1` adipocytes. All these suggest that FetA mediate its inhibitory effect on adiponectin through Wnt3a-PPARγ pathway. Inhibition of adiponectin expression through FetA and Wnt3a significantly compromised with the activation of AMPK and its downstream signalling molecules which adversely affected lipid management causing loss of insulin sensitivity. Downregulation of adiponectin in inflamed adipocyte by FetA through the mediation of Wnt3a and PPARγ is a new report.

Genistein, the Isoflavone in Soybean, Causes Amyloid Beta Peptide Accumulation in Human Neuroblastoma Cell Line: Implications in Alzheimer's Disease.

The isoflavone, genistein, present in soybean is being actively investigated for its potential beneficial effect against Alzheimer's disease. Our data, however, show that in SHSY5Y cells genistein causes increased expression (mRNA and protein) of amyloid precursor protein (APP), increased mRNA expression and activity of ß-secretase and diminished level of insulin degrading enzyme (IDE) which also degrades amyloid beta peptide. These effects of genistein lead to enhanced accumulation of amyloid beta peptide (Aß42) in SHSY5Y cells. The results do not support the view that genistein could be a putative drug against AD and instead strengthen the epidemiological study which implies that genistein content of soybean food product (Tofu) leads to cognitive impairment.

Enhanced ROS production and oxidative damage in subcutaneous white adipose tissue mitochondria in obese and type 2 diabetes subjects.

Oxidative stress in the insulin target tissues has been implicated in the pathophysiology of type 2 diabetes. The study has examined the oxidative stress parameters in the mitochondria of subcutaneous white adipose tissue from obese and non-obese subjects with or without type 2 diabetes. An accumulation of protein carbonyls, fluorescent lipid peroxidation products, and malondialdehyde occurs in the adipose tissue mitochondria of obese type 2 diabetic, non-diabetic obese, and non-obese diabetic subjects with the maximum increase noticed in the obese type 2 diabetes patients and the minimum in non-obese type 2 diabetics. The mitochondria from obese type 2 diabetics, non-diabetic obese, and non-obese type 2 diabetics also produce significantly more reactive oxygen species (ROS) in vitro compared to those of controls, and apparently the mitochondrial ROS production rate in each group is proportional to the respective load of oxidative damage markers. Likewise, the mitochondrial antioxidant enzymes like superoxide dismutase and glutathione peroxidase show decreased activities most markedly in obese type 2 diabetes subjects and to a lesser degree in non-obese type 2 diabetes or non-diabetic obese subjects in comparison to control. The results imply that mitochondrial dysfunction with enhanced ROS production may contribute to the metabolic abnormality of adipose tissue in obesity and diabetes.

Altered serum levels of adipokines and insulin in probable Alzheimer's disease.

Cerebral hypometabolism of glucose, weight loss, and decreased food intake are characteristic features of sporadic Alzheimer's disease (AD). A systematic study on the serum levels of adipokines and insulin, the major hormones regulating energy metabolism, food intake, and body weight, in sporadic AD is necessary. The present study compares the serum levels of leptin, adiponectin, and insulin, measured by commercially available immuno-assay kits, between controls and sporadic AD subjects. The results show a conspicuous decrease in the level of leptin, a dramatic rise in the level of adiponectin, and also a statistically significant increase in insulin level, in the blood of AD subjects, with respect to controls. The changes in the serum levels of adiponectin and insulin in AD are positively correlated with the severity of dementia. Likewise, the serum level of leptin in AD subjects is negatively correlated with the degree of dementia. The changes in the levels of adipokines and insulin have implications in the amyloid pathology, neurodegeneration, and hypometabolism of glucose existing in the AD brain.

Dietary supplementation with N-acetyl cysteine, α-tocopherol and α-lipoic acid reduces the extent of oxidative stress and proinflammatory state in aged rat brain.

The present study has attempted to understand how oxidative stress contributes to the development of proinflammatory state in the brain during aging. Three groups of rats have been used in this study: young (4-6 months, Group I), aged (22-24 months, Group II) and aged with dietary antioxidant supplementation (Group III). The antioxidants were given daily from 18 months onwards in the form of a combination of N-acetyl cysteine (50 mg/100 g body weight), α-lipoic acid (3 mg/100 g body weight), and α-tocopherol (1.5 mg/100 g body weight) till the animals were used for the experiments between 22 and 24 months. Several measurements have been made to evaluate the ROS (reactive oxygen species) production rate, the levels of proinflammatory cytokines (IL-1ß, IL-6 and TNF-α) and the activation status of NF-κß (p65 subunit) in brain of the three groups of rats under the study. Our results reveal that brain aging is accompanied with a significant increase in NADPH oxidase activity and mitochondrial ROS production, a distinct elevation of IL-1ß, IL-6 and TNF-α levels along with increased nuclear translocation of NF-κß (p65 subunit) and all these phenomena are partially but significantly prevented by the long-term dietary antioxidant treatment. The results imply that chronic dietary antioxidants by preventing oxidative stress and proinflammatory state may produce beneficial effects against multiple age-related deficits of the brain.

Mitochondrial bioenergetics is not impaired in nonobese subjects with type 2 diabetes mellitus.

Although mitochondrial dysfunction has been well documented in obese people with type 2 diabetes mellitus, its presence or absence in nonobese subjects with type 2 diabetes mellitus has not been well studied so far. The aim of the present study was to assess the status of mitochondrial oxidative phosphorylation in subcutaneous adipose tissue of nonobese type 2 diabetes mellitus subjects in comparison to control, obese nondiabetic, and obese type 2 diabetes mellitus subjects. Mitochondria were isolated from subcutaneous white adipose tissue obtained from the abdominal region of control, obese nondiabetic, nonobese type 2 diabetes mellitus, and obese type 2 diabetes mellitus subjects. The activities of complex I, I to III, II to III, and IV; transmembrane potential; and inorganic phosphate utilization of mitochondria from different groups were measured. Mitochondrial transmembrane potential, inorganic phosphate utilization, and the activities of respiratory chain complexes were significantly reduced in obese nondiabetic and obese type 2 diabetes mellitus patients compared with those in control subjects. No detectable change in mitochondrial functional parameters was observed in case of nonobese type 2 diabetes mellitus subjects compared with control subjects. Furthermore, a significant difference was noticed in mitochondrial phosphate utilization and activities of respiratory complexes, for example, I, I to III, and II to III, between obese type 2 diabetes mellitus subjects and obese nondiabetic subjects. Obesity modulates mitochondrial dysfunction associated with type 2 diabetes mellitus.