PubMed · 11684643
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F H Messerli. 2001-10-30. Confusing Press Releases and the PREVENT Study.. https://pubmed.ncbi.nlm.nih.gov/11684643/
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Under conditions of iron overload, which are now reaching epidemic proportions worldwide, iron-overload cardiomyopathy is the most important prognostic factor in patient survival. We hypothesize that in iron-overload disorders, iron accumulation in the heart depends on ferrous iron (Fe2+) permeation through the L-type voltage-dependent Ca2+ channel (LVDCC), a promiscuous divalent cation transporter. Iron overload in mice was associated with increased mortality, systolic and diastolic dysfunction, bradycardia, hypotension, increased myocardial fibrosis and elevated oxidative stress. Treatment with LVDCC blockers (CCBs; amlodipine and verapamil) at therapeutic levels inhibited the LVDCC current in cardiomyocytes, attenuated myocardial iron accumulation and oxidative stress, improved survival, prevented hypotension and preserved heart structure and function. Consistent with the role of LVDCCs in myocardial iron uptake, iron-overloaded transgenic mice with cardiac-specific overexpression of the LVDCC alpha1-subunit had twofold higher myocardial iron and oxidative stress levels, as well as greater impairment in cardiac function, compared with littermate controls; LVDCC blockade was again protective. Our results indicate that cardiac LVDCCs are key transporters of iron into cardiomyocytes under iron-overloaded conditions, and potentially represent a new therapeutic target to reduce the cardiovascular burden from iron overload.
Inflammatory responses play an important role in atherosclerosis. To critically assess the effect of dihydropyridines in inflammatory reactions, we conducted a monocyte-endothelial adhesion assay with monocytic THP-1 cells treated with amlodipine under flow conditions in vitro. THP-1 cells were incubated in the presence of amlodipine (10 micromol/L) for 48 hours and then perfused over activated (interleukin-1beta, 10 U/mL, 4 hours) human umbilical vein endothelial cells. The adhesion of THP-1 cells was significantly reduced after amlodipine treatment (P<0.001); however, flow cytometric analysis reveled that the expression levels of integrins in THP-1 cells were not significantly altered. Furthermore, Western blotting analysis of THP-1 cell lysates revealed that translocation of RhoA from the cytosol to the membrane was significantly diminished after amlodipine treatment. In addition, activation of protein kinase C-alpha and -beta, as well as intracellular calcium influx, induced by phorbol 12-myristate 13-acetate, was diminished after amlodipine treatment. Pretreatment of THP-1 cells with calphostin C, a potent inhibitor of protein kinase C, significantly reduced THP-1 adhesion to vascular endothelium, whereas activation of beta1-integrin was reduced after amlodipine treatment in THP-1 cells, based on the immunoreactivity of an activation-specific antibody for beta1-integrin. Similar inhibitory effects were observed when we used freshly isolated peripheral blood mononuclear cells. These findings suggest a potential role for amlodipine in monocyte-endothelial interactions by modulation of protein kinase C- and RhoA-dependent mechanisms, which might account for its vascular protective effects.
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