Aluminium-induced bone disease in uremic rats: effect of deferoxamine

Diosmin, a citrus fruit-derived phlebotonic bioflavonoid protects rats from chronic kidney disease-induced loss of bone mass and strength without deteriorating renal function

Kidney Disease: Improving Global Outcomes (KDIGO) 2017 Clinical Practice Guideline recommended treatment decisions for patients with chronic kidney disease (CKD) with osteoporosis and/or high risk of fracture. Bisphosphonates, the first-line...

Adynamic bone disease: Revisited

The bone and mineral disorders form an integral part of the management of a chronic kidney disease (CKD) patient. Amongst various types of bone pathologies in chronic kidney disease-mineral bone disorder (CKD-MBD), the prevalence of adynamic bone disease (ABD) is increasing. The present review discusses the updated pathophysiology, risk factors, and management of this disorder.

Adynamic bone disease: Revisited

The bone and mineral disorders form an integral part of the management of a chronic kidney disease (CKD) patient. Amongst various types of bone pathologies in chronic kidney disease-mineral bone disorder (CKD-MBD), the prevalence of adynamic bone disease (ABD) is increasing. The present review discusses the updated pathophysiology, risk factors, and management of this disorder.

Fas- and Mitochondria-Mediated Signaling Pathway Involved in Osteoblast Apoptosis Induced by AlCl3

Aluminum (Al) is known to induce apoptosis of osteoblasts (OBs). However, the mechanism is not yet established. To investigate the apoptotic mechanism of OBs induced by aluminum trichloride (AlCl₃), the primary OBs from the craniums of fetal Wistar rats were exposed to 0 mg/mL (control group, CG), 0.06 mg/mL (low-dose group, LG), 0.12 mg/mL (mid-dose group, MG), and 0.24 mg/mL (high-dose group, HG) AlCl₃ for 24 h, respectively. We observed that AlCl₃ induced OB apoptosis with the appearance of apoptotic morphology and increase of apoptosis rate. Additionally, AlCl₃ treatment activated mitochondrial-mediated signaling pathway, accompanied by mitochondrial membrane potential (ΔΨm) depolarization, release of cytochrome c from the mitochondria to the cytoplasm, as well as survival signal-related factor caspase-9 and caspase-3 activation. AlCl₃ exposure also activated Fas/Fas ligand signaling pathway, presented as Fas, Fas ligand, and Fas-associated death domain expression enhancement and caspase-8 activation, as well as the hydrolysis of Bid to truncated Bid, suggesting that the Fas-mediated signaling pathway might aggravate mitochondria-mediated OB apoptosis through hydrolyzing Bid. Furthermore, AlCl₃ exposure inhibited Bcl-2 protein expression and increased the expressions of Bax, Bak, and Bim in varying degrees. These results indicated that AlCl₃ exposure induced OB apoptosis through activating Fas- and mitochondria-mediated signaling pathway and disrupted B-cell lymphoma-2 family proteins.

Aluminum as a toxicant

Although aluminum is the most abundant metal in nature, it has no known biological function. However, it is known that there is a causal role for aluminum in dialysis encephalopathy, microcytic anemia, and osteomalacia. Aluminum has also been proposed to play a role in the pathogenesis of Alzheimer’s disease (AD) even though this issue is controversial. The exact mechanism of aluminum toxicity is not known but accumulating evidence suggests that the metal can potentiate oxidative and inflammatory events, eventually leading to tissue damage. This review encompasses the general toxicology of aluminum with emphasis on the potential mechanisms by which it may accelerate the progression of chronic age-related neurodegenerative disorders.

A magnesium based phosphate binder reduces vascular calcification without affecting bone in chronic renal failure rats

The alternative phosphate binder calcium acetate/magnesium carbonate (CaMg) effectively reduces hyperphosphatemia, the most important inducer of vascular calcification, in chronic renal failure (CRF). In this study, the effect of low dose CaMg on vascular calcification and possible effects of CaMg on bone turnover, a persistent clinical controversy, were evaluated in chronic renal failure rats. Adenine-induced CRF rats were treated daily with 185 mg/kg CaMg or vehicle for 5 weeks. The aortic calcium content and area% calcification were measured to evaluate the effect of CaMg. To study the effect of CaMg on bone remodeling, rats underwent 5/6th nephrectomy combined with either a normal phosphorus diet or a high phosphorus diet to differentiate between possible bone effects resulting from either CaMg-induced phosphate deficiency or a direct effect of Mg. Vehicle or CaMg was administered at doses of 185 and 375 mg/kg/day for 8 weeks. Bone histomorphometry was performed. Aortic calcium content was significantly reduced by 185 mg/kg/day CaMg. CaMg ameliorated features of hyperparathyroid bone disease. In CRF rats on a normal phosphorus diet, the highest CaMg dose caused an increase in osteoid area due to phosphate depletion. The high phosphorus diet combined with the highest CaMg dose prevented the phosphate depletion and thus the rise in osteoid area. CaMg had no effect on osteoblast/osteoclast or dynamic bone parameters, and did not alter bone Mg levels. CaMg at doses that reduce vascular calcification did not show any harmful effect on bone turnover.

Pro-inflammatory effects of aluminum in human glioblastoma cells

Inflammatory events have been associated with senile plaques, one of the pathological hallmarks of Alzheimer's disease (AD). It is believed that aggregated beta-amyloid (betaA) proteins, which form the core of these plaques, may be responsible for triggering the inflammatory reaction. In the present study, the ability of aluminum (Al) to initiate similar inflammatory events was investigated in a human glioblastoma cell line. A 6-day exposure to either lipopolysaccharide (LPS) or aluminum sulfate caused a significant increase in the rate of proliferation of the glioblastoma cells. Both treatments also caused activation of the immune-responsive transcription factor NF-kappaB although there were time-related differences. The levels of secreted cytokines, interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) were both increased by the LPS treatment although exposure to Al decreased the secretion of the former while elevating the levels of the latter. These events may be due to the activation of glial cells and subsequent stress response to either Al complexes or LPS. Although exposure to either stress factor caused a stimulation of inflammatory markers, there were time-dependent differences in the response. This may reflect the ability of the cells to discern different stress factors and thus orchestrate an innate immune response profile distinct to each immunogen.

Comparative aluminum mobilizing actions of deferoxamine and four 3-hydroxypyrid-4-ones in aluminum-loaded rats

The efficacy of the Al chelating drugs deferoxamine (DFO) and the hydoxypyridones (HPs): 1,2-dimethyl-3-hydroxypyrid-4-one (L1), 1-[3-hydroxy-2-methyl-4-oxopyridyl]-2-ethanesulfonic acid (L6), 1-benzyl-(4-carboxylic acid)-3-hydroxy-2-methyl-4-oxopyridine (Bzcal) and 1-(p-methylbenzyl)-2-ethyl-3-hydroxypyrid-4-one (MeBzEM) in increasing Al excretion and reducing tissue Al accumulation has been compared in adult male rats which had previously received Al nitrate nonahydrate i.p. at 0.16 mmol/kg per day for 2 months. At the end of this period, DFO was injected s.c. and the HPs were given by gavage at 0.89 mmol/kg per day for five consecutive days. Total urines were collected 24 h after each chelator administration. Following chelation treatment animals were killed and samples of brain, bone, liver, kidney, and spleen were collected. DFO administration increased to about 4 x the cumulative urinary Al elimination for 5 days, while the excretion of Al into urine caused by Bzcal, L1, and MeBzEM administration was about twice that of the control group. On the other hand, treatment with Bzcal, DFO, and MeBzEM for 5 days significantly reduced the Al levels in bone by 31, 33, and 29%, and the Al concentrations in brain by 46, 69, and 71%, respectively. These results suggest that oral administrations of MeBzEM and Bzcal can be potential alternatives to parenteral administration of DFO in Al removal.