Aluminum ions stimulate the oxidizability of low density lipoprotein by Fe2+: Implication in hemodialysis mediated atherogenic LDL modification

A review of the epidemiological and laboratory evidence of the role of aluminum exposure in pathogenesis of cardiovascular diseases

The objective of the present study was to review the epidemiological and laboratory evidence on the role of aluminum (Al) exposure in the pathogenesis of cardiovascular diseases. Epidemiological data demonstrated an increased incidence of cardiovascular diseases (CVD), including hypertension and atherosclerosis in occupationally exposed subjects and hemodialysis patients. In addition, Al body burden was found to be elevated in patients with coronary heart disease, hypertension, and dyslipidemia. Laboratory studies demonstrated that Al exposure induced significant ultrastructural damage in the heart, resulting in electrocardiogram alterations in association with cardiomyocyte necrosis and apoptosis, inflammation, oxidative stress, inflammation, and mitochondrial dysfunction. In agreement with the epidemiological findings, laboratory data demonstrated dyslipidemia upon Al exposure, resulting from impaired hepatic lipid catabolism, as well as promotion of low-density lipoprotein oxidation. Al was also shown to inhibit paraoxonase 1 activity and to induce endothelial dysfunction and adhesion molecule expression, further promoting atherogenesis. The role of Al in hypertension was shown to be mediated by up-regulation of NADPH-oxidase, inhibition of nitric oxide bioavailability, and stimulation of renin-angiotensin-aldosterone system. It has been also demonstrated that Al exposure targets cerebral vasculature, which may be considered a link between Al exposure and cerebrovascular diseases. Findings from other tissues lend support that ferroptosis, pyroptosis, endoplasmic reticulum stress, and modulation of gut microbiome and metabolome are involved in the development of CVD upon Al exposure. A better understanding of the role of the cardiovascular system as a target for Al toxicity will be useful for risk assessment and the development of treatment and prevention strategies.

Shift from darbepoetin-α to continuous erythropoietin receptor activator decreases serum aluminium concentration in patients on hemodialysis

OBJECTIVE

The response of erythropoietic stimulating agents (ESA) in uremic patients may be associated with the changes of biochemical parameters, metal elements and inflammation status during the shift from one ESA to another.

METHOD

We compared changes in above mentioned factors after switching from darbepoetin-α (DPO) 20μg weekly for 10 weeks to continuous erythropoietin receptor activator (CERA) 100μg monthly for 10 weeks in uremic patients on hemodialysis. The haematocrit (Hct), metal elements and inflammation status are the primary outcome. Subjects included 54 patients without transfusion or bleeding or additional ESAs. Responders (IR, n=36) were defined as patients with an increase in Hct after the swtich.

RESULT

Although there was no significant difference in overall mean Hct after the switch (p=0.135), there are significantly greater mean number of red blood cells (RBC) (p=0.006), higher platelet numbers (p=0.001), larger RBCs (p=0.017) and higher creatinine (p=0.04) and total cholesterol (T-CHOL) (p=0.003) levels. Mean overall aluminium (Al) level decreased significantly (p=0.001). C-reactive protein (CRP) also decreased (p=0.016). The overall LDH increased (p=0.049) and potassium decreased significantly (p=0.036), which indicating active erythropoiesis. The calcium (Ca) level was significantly higher (p=0.034) and phosphate was significantly lower (p=0.028) after the shift. Although there was no significant increase in overall levels of parathyroid hormone (PTH) after the shift (p=0.061), but the pre-shift and post-shift PTH level was significantly higher in IRs than in non-IRs (p=0.003 and p=0.027, respectively). IRs had a significantly lower initial T-CHOL (p=0.03) and initial CRP (p=0.012) than non-responders, which may be related to lower inflammation.

CONCLUSION

We found the shift from DPO to CERA results in lower Al levels, a reduced inflammatory response, and an increase in RBC number and PTH level in uremic patients on hemodialysis.

Circulating levels of metals are related to carotid atherosclerosis in elderly

The aim of this study was to investigate if blood levels of trace and/or heavy metals are related to atherosclerosis in a cross-sectional study in elderly. In the population-based Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study (1016 subjects, all aged 70), the prevalence of carotid artery plaques was recorded by ultrasound. The numbers of carotid arteries with plaques (0, 1 or 2) were recorded. Also the thickness (IMT) and gray scale (IM-GSM) of the intima-media complex were measured together with plaque echogenicity. Eleven heavy metals and trace elements were analyzed in whole blood, using inductively coupled plasma-sector field mass spectrometry. Nickel levels were related to the number of carotid arteries with plaques in an inverted U-shaped manner after multiple adjustment for gender, waist circumference, body mass index, fasting blood glucose, systolic and diastolic blood pressure, HDL and LDL cholesterol, serum triglycerides, smoking, antihypertensive treatment and statin use (p=0.026). IM-GSM and plaque echogenicity were both inversely related to chromium in a linear fashion, and to aluminum in an inverted U-shaped manner (both p<0.0001 for IM-GSM). The relationships between metals and IMT were modest. Circulating levels of some metals, like nickel, aluminum and chromium, were related to atherosclerotic plaques or the echogenicity of the IM-GSM and overt plaques independently of cardiovascular risk factors, including lipids.

Cardiac and vascular metal deposition with high mortality in nephrogenic systemic fibrosis

Nephrogenic systemic fibrosis is a severe disabling disease that can follow gadolinium-based contrast exposure. In this study we analyzed the clinical and laboratory records of patients with nephrogenic systemic fibrosis who had a history of exposure to gadolinium-based contrast media and identified their cardiac and vascular events. At autopsy, we found that the heart, blood vessels, and skin of three patients who died of cardiac and/or vascular complications had appreciable amounts of gadolinium, iron, and aluminum as measured by inductively coupled plasma-mass spectrometry and confirmed by x-ray fluorescence. Of the 32 patients with nephrogenic systemic fibrosis studied, 10 died at a median of 112 days after diagnosis. Cardiovascular events contributed to the mortality of 9 patients and included congestive heart failure, recurrent arrhythmias, hypotension, stroke, limb ischemia, posterior ischemic optic neuropathy and sudden death. Our results show that increased cardiac and vascular complications along with short survival in nephrogenic systemic fibrosis are associated with metal accumulation in the heart, blood vessels, and skin of these patients.

Aluminum compounds enhance lipid peroxidation in liposomes: Insight into cellular damage caused by oxidative stress

Aluminum (Al) has been proposed as one of the critical environmental factors responsible for several neurodegenerative diseases such as Alzheimer's disease. However, the suggested mechanism involving the contribution of reactive oxygen species still remains controversial. We have first attempted to identify Al compounds either in its ionic or complexed forms that cause oxidative stress in biological systems. For this purpose, we examined the effect of inorganic Fe(2+)- and organic radical initiator (2,2'-azobis (2-amidinopopane) hydrochloride; AAPH)-induced lipid peroxidation by using aluminum (Al(3+)) nitrate and tris(maltolato)aluminum(III) complex (ALM) with respect to molecular oxygen (O(2)) consumption and membrane fluidity change in liposomes as biological membrane models. The following important results were obtained: (1) ALM enhanced the lipid peroxidation induced by Fe(2+) and AAPH in phosphatidylcholine liposomes; this corresponded well with the promotion of O(2) uptake in the same liposomes, (2) Al(3+) increased both lipid peroxidation and O(2) consumption in phosphatidylserine liposomes in the presence of Fe(2+), and (3) both Al(3+) and ALM affected the membrane fluidity on the inner side. It has been concluded that ALM induces higher lipid peroxidation in liposomes than Al(3+); this finding will be useful to gain an insight into the role of Al in cellular damage in relation to oxidative stress.