Dose-Dependent Effects of Lipopolysaccharide on the Endothelium-Sepsis versus Metabolic Endotoxemia-Induced Cellular Senescence.

The endothelium, the innermost cell layer of blood vessels, is not only a physical barrier between the bloodstream and the surrounding tissues but has also essential functions in vascular homeostasis. Therefore, it is not surprising that endothelial dysfunction is associated with most cardiovascular diseases. The functionality of the endothelium is compromised by endotoxemia, the presence of bacterial endotoxins in the bloodstream with the main endotoxin lipopolysaccharide (LPS). Therefore, this review will focus on the effects of LPS on the endothelium. Depending on the LPS concentration, the outcomes are either sepsis or, at lower concentrations, so-called low-dose or metabolic endotoxemia. Sepsis, a life-threatening condition evoked by hyperactivation of the immune response, includes breakdown of the endothelial barrier resulting in failure of multiple organs. A deeper understanding of the underlying mechanisms in the endothelium might help pave the way to new therapeutic options in sepsis treatment to prevent endothelial leakage and fatal septic shock. Low-dose endotoxemia or metabolic endotoxemia results in chronic inflammation leading to endothelial cell senescence, which entails endothelial dysfunction and thus plays a critical role in cardiovascular diseases. The identification of compounds counteracting senescence induction in endothelial cells might therefore help in delaying the onset or progression of age-related pathologies. Interestingly, two natural plant-derived substances, caffeine and curcumin, have shown potential in preventing endothelial cell senescence.

Caffeine Inhibits Oxidative Stress- and Low Dose Endotoxemia-Induced Senescence-Role of Thioredoxin-1.

The maintenance of Thioredoxin-1 (Trx-1) levels, and thus of cellular redox homeostasis, is vital for endothelial cells (ECs) to prevent senescence induction. One hallmark of EC functionality, their migratory capacity, which depends on intact mitochondria, is reduced in senescence. Caffeine improves the migratory capacity and mitochondrial functionality of ECs. However, the impact of caffeine on EC senescence has never been investigated. Moreover, a high-fat diet, which can induce EC senescence, results in approximately 1 ng/mL lipopolysaccharide (LPS) in the blood. Therefore, we investigated if low dose endotoxemia induces EC senescence and concomitantly reduces Trx-1 levels, and if caffeine prevents or even reverses senescence. We show that caffeine precludes H2O2-triggered senescence induction by maintaining endothelial NO synthase (eNOS) levels and preventing the elevation of p21. Notably, 1 ng/mL LPS also increases p21 levels and reduces eNOS and Trx-1 amounts. These effects are completely blocked by co-treatment with caffeine. This prevention of senescence induction is similarly accomplished by the permanent expression of mitochondrial p27, a downstream effector of caffeine. Most importantly, after senescence induction by LPS, a single bolus of caffeine inhibits the increase in p21. This treatment also blocks Trx-1 degradation, suggesting that the reversion of senescence is intimately associated with a normalized redox balance.

Aryl Hydrocarbon Receptor-Dependent and -Independent Pathways Mediate Curcumin Anti-Aging Effects.

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor whose activity can be modulated by polyphenols, such as curcumin. AhR and curcumin have evolutionarily conserved effects on aging. Here, we investigated whether and how the AhR mediates the anti-aging effects of curcumin across species. Using a combination of in vivo, in vitro, and in silico analyses, we demonstrated that curcumin has AhR-dependent or -independent effects in a context-specific manner. We found that in Caenorhabditis elegans, AhR mediates curcumin-induced lifespan extension, most likely through a ligand-independent inhibitory mechanism related to its antioxidant activity. Curcumin also showed AhR-independent anti-aging activities, such as protection against aggregation-prone proteins and oxidative stress in C. elegans and promotion of the migratory capacity of human primary endothelial cells. These AhR-independent effects are largely mediated by the Nrf2/SKN-1 pathway.

Protective Effects of Curcumin in Cardiovascular Diseases-Impact on Oxidative Stress and Mitochondria.

Cardiovascular diseases (CVDs) contribute to a large part of worldwide mortality. Similarly, two of the major risk factors for these diseases, aging and obesity, are also global problems. Aging, the gradual decline of body functions, is non-modifiable. Obesity, a modifiable risk factor for CVDs, also predisposes to type 2 diabetes mellitus (T2DM). Moreover, it affects not only the vasculature and the heart but also specific fat depots, which themselves have a major impact on the development and progression of CVDs. Common denominators of aging, obesity, and T2DM include oxidative stress, mitochondrial dysfunction, metabolic abnormalities such as altered lipid profiles and glucose metabolism, and inflammation. Several plant substances such as curcumin, the major active compound in turmeric root, have been used for a long time in traditional medicine and for the treatment of CVDs. Newer mechanistic, animal, and human studies provide evidence that curcumin has pleiotropic effects and attenuates numerous parameters which contribute to an increased risk for CVDs in aging as well as in obesity. Thus, curcumin as a nutraceutical could hold promise in the prevention of CVDs, but more standardized clinical trials are required to fully unravel its potential.

Repurposing the serotonin agonist Tegaserod as an anticancer agent in melanoma: molecular mechanisms and clinical implications.

BACKGROUND: New therapies are urgently needed in melanoma particularly in late-stage patients not responsive to immunotherapies and kinase inhibitors. METHODS: Drug screening, IC50 determinations as well as synergy assays were detected by the MTT assay. Apoptosis using Annexin V and 7AAD staining was assessed using flow cytometry. TUNEL staining was performed using immunocytochemistry. Changes in phosphorylation of key molecules in PI3K/Akt/mTOR and other relevant pathways were detected by western blot as well as immunocytochemistry. To assess in vivo anti-tumor activity of Tegaserod, syngeneic intravenous and subcutaneous melanoma xenografts were used. Immunocytochemical staining was performed to detect expression of active Caspase-3, cleaved Caspase 8 and p-S6 in tumors. Evaluation of immune infiltrates was carried out by flow cytometry. RESULTS: Using a screen of 770 pharmacologically active and/or FDA approved drugs, we identified Tegaserod (Zelnorm, Zelmac) as a compound with novel anti-cancer activity which induced apoptosis in murine and human malignant melanoma cell lines. Tegaserod (TM) is a serotonin receptor 4 agonist (HTR4) used in the treatment of irritable bowel syndrome (IBS). TM's anti-melanoma apoptosis-inducing effects were uncoupled from serotonin signaling and attributed to PI3K/Akt/mTOR signaling inhibition. Specifically, TM blunted S6 phosphorylation in both BRAFV600E and BRAF wildtype (WT) melanoma cell lines. TM decreased tumor growth and metastases as well as increased survival in an in vivo syngeneic immune-competent model. In vivo, TM also caused tumor cell apoptosis, blunted PI3K/Akt/mTOR signaling and decreased S6 phosphorylation. Furthermore TM decreased the infiltration of immune suppressive regulatory CD4+CD25+ T cells and FOXP3 and ROR-γt positive CD4+ T cells. Importantly, TM synergized with Vemurafenib, the standard of care drug used in patients with late stage disease harboring the BRAFV600E mutation and could be additively or synergistically combined with Cobimetinib in both BRAFV600E and BRAF WT melanoma cell lines in inducing anti-cancer effects. CONCLUSION: Taken together, we have identified a drug with anti-melanoma activity in vitro and in vivo that has the potential to be combined with the standard of care agent Vemurafenib and Cobimetinib in both BRAFV600E and BRAF WT melanoma.