Pharmacological depletion of RNA splicing factor RBM39 by indisulam synergizes with PARP inhibitors in high-grade serous ovarian carcinoma.

Ovarian high-grade serous carcinoma (HGSC) is the most common subtype of ovarian cancer with limited therapeutic options and a poor prognosis. In recent years, poly-ADP ribose polymerase (PARP) inhibitors have demonstrated significant clinical benefits, especially in patients with BRCA1/2 mutations. However, acquired drug resistance and relapse is a major challenge. Indisulam (E7070) has been identified as a molecular glue that brings together splicing factor RBM39 and DCAF15 E3 ubiquitin ligase resulting in polyubiquitination, degradation, and subsequent RNA splicing defects. In this work, we demonstrate that the loss of RBM39 induces splicing defects in key DNA damage repair genes in ovarian cancer, leading to increased sensitivity to cisplatin and various PARP inhibitors. The addition of indisulam also improved olaparib response in mice bearing PARP inhibitor-resistant tumors. These findings demonstrate that combining RBM39 degraders and PARP inhibitors is a promising therapeutic approach to improve PARP inhibitor response in ovarian HGSC.

Lactic acidosis induces resistance to the pan-Akt inhibitor uprosertib in colon cancer cells.

BACKGROUND: Akt signalling regulates glycolysis and drives the Warburg effect in cancer, thus decreased glucose utilisation is a pharmacodynamic marker of Akt inhibition. However, cancer cells can utilise alternative nutrients to glucose for energy such as lactate, which is often elevated in tumours together with increased acidity. We therefore hypothesised that lactic acidosis may confer resistance to Akt inhibition. METHODS: The effect of the pan-Akt inhibitor uprosertib (GSK2141795), on HCT116 and LS174T colon cancer cells was evaluated in the presence and absence of lactic acid in vitro. Expression of downstream Akt signalling proteins was determined using a phosphokinase array and immunoblotting. Metabolism was assessed using 1H nuclear magnetic resonance spectroscopy, stable isotope labelling and gas chromatography-mass spectrometry. RESULTS: Lactic acid-induced resistance to uprosertib was characterised by increased cell survival and reduced apoptosis. Uprosertib treatment reduced Akt signalling and glucose uptake irrespective of lactic acid supplementation. However, incorporation of lactate carbon and enhanced respiration was maintained in the presence of uprosertib and lactic acid. Inhibiting lactate transport or oxidative phosphorylation was sufficient to potentiate apoptosis in the presence of uprosertib. CONCLUSIONS: Lactic acidosis confers resistance to uprosertib, which can be reversed by inhibiting lactate transport or oxidative metabolism.

Nrf2 deficiency aggravates Angiotensin II-induced cardiac injury by increasing hypertrophy and enhancing IL-6/STAT3-dependent inflammation.

BACKGROUND: NF-E2-related factor 2 (Nrf2) is a transcription factor playing cytoprotective effects in various pathological processes including oxidative stress and cardiac hypertrophy. Despite being a potential therapeutic target to treat several cardiomyopathies, the signaling underlying Nrf2-dependent cardioprotective action remains largely uncharacterized. AIM: This study aimed to explore the signaling mediating the role of Nrf2 in the development of hypertensive cardiac pathogenesis by analyzing the response to Angiotensin II (Ang II) in the presence or absence of Nrf2 expression, both in vivo and in vitro. RESULTS: Our results indicated that Nrf2 deficiency exacerbated cardiac damage triggered by Ang II infusion. Mechanistically, our study shows that Ang II-triggered hypertrophy and inflammation is exacerbated in the absence of Nrf2 expression and points to the involvement of the IL-6/STAT3 signaling pathway in this event. Indeed, our results show that IL-6 abundance triggered by Ang II is increased in the absence of Nrf2 and demonstrate the requirement of IL-6 in STAT3 activation and cardiac inflammation induced by Ang II. CONCLUSION: Our results show that Nrf2 is important for the protection of the heart against Ang II-induced cardiac hypertrophy and inflammation by mechanisms involving the regulation of IL-6/STAT3-dependent signaling.

IL-6: A Potential Role in Cardiac Metabolic Homeostasis.

Interleukin-6 (IL-6) is implicated in multiple biological functions including immunity, neural development, and haematopoiesis. Recently, mounting evidence indicates that IL-6 plays a key role in metabolism, especially lipid metabolic homeostasis. A working heart requires a high and constant energy input which is largely generated by fatty acid (FA) ß-oxidation. Under pathological conditions, the precise balance between cardiac FA uptake and metabolism is perturbed so that excessive FA is accumulated, thereby predisposing to myocardial dysfunction (cardiac lipotoxicity). In this review, we summarize the current evidence that suggests the involvement of IL-6 in lipid metabolism. Cardiac metabolic features and consequences of myocardial lipotoxicity are also briefly analyzed. Finally, the roles of IL-6 in cardiac FA uptake (i.e., serum lipid profile and myocardial FA transporters) and FA metabolism (namely, ß-oxidation, mitochondrial function, biogenesis, and FA de novo synthesis) are discussed. Overall, understanding how IL-6 transmits signals to affect lipid metabolism in the heart might allow for development of better clinical therapies for obesity-associated cardiac lipotoxicity.

Deletion of protein kinase B2 preserves cardiac function by blocking interleukin-6-mediated injury and restores blood pressure during angiotensin II/high-salt-diet-induced hypertension.

OBJECTIVE: Protein kinase B2 (AKT2) is implicated in cardiomyocyte survival during various stress conditions. However, the role of AKT2 in heart function, cardiac hypertrophy and blood pressure (BP) control during hypertension is not fully understood. Therefore, we sought to determine whether the deletion of AKT2 protects cardiac function during angiotensin II/high-salt-diet (AngII/HSD) treatment and find out the signaling pathway. METHODS: Male C57BL/6J (wild type), AKT2 knockout and interleukin (IL)-6 knockout mice were fed a 4% NaCl diet for 5 weeks. In the last week, mice were split in two groups and infused subcutaneously with either vehicle or AngII (1.5 µg/h per mouse) for 1 week. Then, BP and cardiac function were assessed. Immunohistology of IL-6 and monocyte chemoattractant protein 1 was performed to detect inflammation in the heart. Masson's trichrome staining was performed to evaluate cardiac fibrosis. Heart tissue homogenates and neonatal mice cardiomyocytes were collected to analyze oxidative stress. RESULTS: Compared with wild-type mice, AKT2 knockout mice maintained BP and showed better left ventricle ejection fraction, lower level of fibrosis, reduced oxidative stress, reduced IL-6 expression and less macrophage infiltration, when treated with AngII/HSD. IL-6 knockout mice treated with AngII/HSD also showed alleviated left ventricular function, fibrosis, oxidative stress and macrophage infiltration compared with wild type. CONCLUSION: AKT2 deficiency prevents the development of AngII/HSD-induced hypertension, cardiac dysfunction and myocardial injury including oxidative stress, fibrosis and inflammation by suppressing IL-6 expression. These data reveal an important role of the AKT2-IL-6 pathway in mediating AngII/HSD-induced hypertension and cardiomyopathy.

AKT2 deficiency induces retardation of myocyte development through EndoG-MEF2A signaling in mouse heart.

Protein kinase B2 (AKT2) is implicated in diverse process of cardiomyocyte signaling including survival and metabolism. However, the role of AKT2 in myocardium development and the signaling pathway is rarely understood. Therefore, we sought to determine the effect of AKT2 deletion on heart development and its downstream targets. By using experimental animal models and neonatal rat cardiomyocytes (NRCMs), we observed that AKT2 deficiency induces retardation of heart development and increased systemic blood pressure (BP) without affecting cardiac function. Further investigation suggested that deficiency of AKT2 in myocardium results in diminished MEF2A abundance, which induced decreased size of cardiomyocytes. We additionally confirmed that EndoG, which is also regulated by AKT2, is a suppressor of MEF2A in myocardium. Finally, our results proved that AKT2 deficiency impairs the response to ß-adrenergic stimuli that normally causes hypertrophy in cardiomyocytes by downregulating MEF2A expression. Our data are the first to show the important role of AKT2 in determining the size of myocardium, its deficiency causes retardation of cardiomyocyte development. We also proved a novel pathway of heart development involving EndoG and MEF2A regulated by AKT2.

Interleukin-6 deficiency attenuates angiotensin II-induced cardiac pathogenesis with increased myocyte hypertrophy.

Interleukin-6 (IL-6) signaling is critical for cardiomyocyte hypertrophy, while the role of IL-6 in the pathogenesis of myocardium hypertrophy remains controversial. To determine the essential role of IL-6 signaling for the cardiac development during AngII-induced hypertension, and to elucidate the mechanisms, wild-type (WT) and IL-6 knockout (IL-6 KO) mice were infused subcutaneously with either vehicle or AngII (1.5 µg/h/mouse) for 1 week. Immunohistological and serum studies revealed that the extents of cardiac fibrosis, inflammation and apoptosis were reduced in IL-6 KO heart during AngII-stimulation, while cardiac hypertrophy was obviously induced. To investigate the underlying mechanisms, by using myocardial tissue and neonatal cardiomyocytes, we observed that IL-6/STAT3 signaling was activated under the stimulation of AngII both in vivo and in vitro. Further investigation suggested that STAT3 activation enhances the inhibitory effect of EndoG on MEF2A and hampers cardiomyocyte hypertrophy. Our study is the first to show the important role of IL-6 in regulating cardiac pathogenesis via inflammation and apoptosis during AngII-induced hypertension. We also provide a novel link between IL-6/STAT3 and EndoG/MEF2A pathway that affects cardiac hypertrophy during AngII stimulation.

Interleukin-6 deficiency facilitates myocardial dysfunction during high fat diet-induced obesity by promoting lipotoxicity and inflammation.

OBJECTIVE: Obesity is associated with metabolic disorder and chronic inflammation that plays a crucial role in cardiovascular diseases. IL-6 is involved in regulating obesity-related lipid metabolism and inflammation. In this study, we sought to determine the role of IL-6 in high-fat diet (HFD)-induced cardiomyopathy and explore the signaling pathway. METHODS: Female, 5-week-old IL-6 knockout (KO) and littermate mice were fed a normal diet (ND, 10% fat) or HFD (45% fat) for 14 weeks. At the end of treatment, cardiac function was assessed by echocardiography. Adipose tissues and plasma were collected for further measurement. Immunohistology of CD68 was performed to detect inflammation in the heart. Masson's trichrome staining and Oil Red O staining was applied to evaluated cardiac fibrosis and lipid accumulation. Real-time PCR and Western immunoblotting analyses on heart tissue were used to explore the underlying mechanism. RESULTS: IL-6 KO mice displayed increased insulin resistance compared to WT mice at baseline. When fed HFD, IL-6 KO mice showed decreased gains in body weight and fat mass, increased insulin resistance relative to IL-6 KO mice feed ND. Furthermore, IL-6 KO mice developed cardiac dysfunction during HFD-induced obesity. Histological analysis suggested increased lipid accumulation, fibrosis and inflammation without affecting cardiac morphology during HFD treatment in the heart of IL-6 KO mice. Finally, IL-6 deficiency increased the phosphorylation of AMPK and ACC in the heart during HFD-induced obesity. CONCLUSION: Our results suggest that IL-6 contributes to limit lipid metabolic disorder, cardiac hypertrophy, fibrosis, inflammation and myocardium lipotoxicity during HFD-induced obesity.

AKT2 Blocks Nucleus Translocation of Apoptosis-Inducing Factor (AIF) and Endonuclease G (EndoG) While Promoting Caspase Activation during Cardiac Ischemia.

The AKT (protein kinase B, PKB) family has been shown to participate in diverse cellular processes, including apoptosis. Previous studies demonstrated that protein kinase B2 (AKT2-/-) mice heart was sensitized to apoptosis in response to ischemic injury. However, little is known about the mechanism and apoptotic signaling pathway. Here, we show that AKT2 inhibition does not affect the development of cardiomyocytes but increases cell death during cardiomyocyte ischemia. Caspase-dependent apoptosis of both the extrinsic and intrinsic pathway was inactivated in cardiomyocytes with AKT2 inhibition during ischemia, while significant mitochondrial disruption was observed as well as intracytosolic translocation of cytochrome C (Cyto C) together with apoptosis-inducing factor (AIF) and endonuclease G (EndoG), both of which are proven to conduct DNA degradation in a range of cell death stimuli. Therefore, mitochondria-dependent cell death was investigated and the results suggested that AIF and EndoG nucleus translocation causes cardiomyocyte DNA degradation during ischemia when AKT2 is blocked. These data are the first to show a previous unrecognized function and mechanism of AKT2 in regulating cardiomyocyte survival during ischemia by inducing a unique mitochondrial-dependent DNA degradation pathway when it is inhibited.