Elucidating the Association Between the Upregulation of Angiotensin Type 1-Receptors and the Development of Gastrointestinal Malignancies

Impacts of SARS-CoV-2 on brain renin angiotensin system related signaling and its subsequent complications on brain: A theoretical perspective

Cellular ACE2 (cACE2), a vital component of the renin-angiotensin system (RAS), possesses catalytic activity to maintain AngII and Ang 1-7 balance, which is necessary to prevent harmful effects of AngII/AT2R and promote protective pathways of Ang (1-7)/MasR and Ang (1-7)/AT2R. Hemostasis of the brain-RAS is essential for maintaining normal central nervous system (CNS) function. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a viral disease that causes multi-organ dysfunction. SARS-CoV-2 mainly uses cACE2 to enter the cells and cause its downregulation. This, in turn, prevents the conversion of Ang II to Ang (1-7) and disrupts the normal balance of brain-RAS. Brain-RAS disturbances give rise to one of the pathological pathways in which SARS-CoV-2 suppresses neuroprotective pathways and induces inflammatory cytokines and reactive oxygen species. Finally, these impairments lead to neuroinflammation, neuronal injury, and neurological complications. In conclusion, the influence of RAS on various processes within the brain has significant implications for the neurological manifestations associated with COVID-19. These effects include sensory disturbances, such as olfactory and gustatory dysfunctions, as well as cerebrovascular and brain stem-related disorders, all of which are intertwined with disruptions in the RAS homeostasis of the brain.

Inhibition of angiotensin II type 1 receptor by candesartan reduces tumor growth and ameliorates fibrosis in colorectal cancer

Colorectal cancer (CRC) is an important cause of cancer-related mortality. Aberrant activation of the renin-angiotensin system (RAS) is reported to be associated with poor clinical outcomes in patients with CRC. This study was designed to explore the anti-tumor effects of the angiotensin receptor blocker Candesartan either alone or in combination with 5-FU in in vitro and in vivo models of CRC. The cytotoxic effects of Candesartan were assessed using the MTT assay in two colorectal cancer cell lines (CT-26 and SW-480). To investigate the potential regulatory role of Candesartan on tumor growth, apoptosis, and migration, the expression levels of Cyclin D1, Survivin, MMP3, MMP9, and E-cadherin mRNAs were evaluated. The oxidant/antioxidant balance was also examined by determining the levels of MDA, thiols, SOD, and CAT. We used a xenograft model of colon cancer to investigate the effects of Candesartan alone, or in combination with 5-FU, on tumor growth following histological staining (Hematoxylin & Eosin and Masson trichrome staining) and biochemical studies as well as gene expression analyses by RT-PCR and western blotting. Candesartan suppressed tumor cell proliferation and migration by modulating Cyclin D1, MMP3/9, and E-cadherin. Treatment with Candesartan either alone, or in combination with 5-FU decreased tumor size in the mouse model, and also increased the level of oxidative markers MDA and reduced CAT, SOD, and thiols. Histological evaluation showed that Candesartan increased tumor necrosis, reduced tumor density and attenuated collagen deposition reducing tumor fibrosis in tumor xenograft. Candesartan, an inhibitor of the RAS, when used in combination with 5-FU reduced tumor growth by inhibiting fibrosis and inducing ROS production, supporting further clinical studies on this therapeutic approach for treatment of CRC.