RANKL Is a Mediator of Bone Resorption in Idiopathic Hypercalciuria

Background and objectives: This study aimed to determine the expression of osteoprotegerin, receptor activator of nuclear factor κB ligand, interleukin-1α, transforming growth factor-β, and basic fibroblast growth factor in stone-forming patients with idiopathic hypercalciuria.Design, setting, participants, & measurements: Immunohistochemical analysis was performed in undecalcified bone samples previously obtained from 36 transiliac bone biopsies of patients who had idiopathic hypercalciuria and whose histomorphometry had shown lower bone volume, increased bone resorption, and prolonged mineralization lag time.Results: Bone expression of receptor activator of nuclear factor κB ligand and osteoprotegerin was significantly higher in patients with idiopathic hypercalciuria versus control subjects. Transforming growth factor-β immunostaining was lower in patients with idiopathic hypercalciuria than in control subjects and correlated directly with mineralization surface. Interleukin-1α and basic fibroblast growth factor staining did not differ between groups. Receptor activator of nuclear factor κB ligand bone expression was significantly higher in patients who had idiopathic hypercalciuria and exhibited higher versus normal bone resorption.Conclusion: A higher expression of receptor activator of nuclear factor κB ligand in bone tissue suggests that increased bone resorption in patients with idiopathic hypercalciuria is mediated by receptor activator of nuclear factor κB ligand. Osteoprotegerin bone expression might have been secondarily increased in an attempt to counteract the actions of receptor activator of nuclear factor κB ligand. The low bone expression of transforming growth factor-β could contribute to the delayed mineralization found in such patients.The most common metabolic abnormality in patients with nephrolithiasis, occurring in up to 50% of patients, is idiopathic hypercalciuria (IH), characterized by an increased intestinal calcium absorption (1,2) and bone resorption (3) and decreased renal tubular calcium reabsorption. Decreased bone mineral density (BMD) in trabecular and cortical bone has been reported in several series of patients with IH (4–10), and some studies also reported an increase of bone resorption markers (7,8). In a population-based retrospective cohort study, the percentage of calcium stone-forming (CSF) patients with a first vertebral fracture was more than four times the expected rates in the general population (11).Abnormal bone histomorphometry in patients with hypercalciuria was previously described by our group (4–6) as well as by other investigators (12–16). Main findings included increased bone resorption, low bone formation, and a mineralization defect. Literature data suggested that the elevation of cytokines such as IL-1, IL-6, and TNF-α in peripheral blood monocytes could be responsible for increasing bone resorption, raising the hypothesis that bone resorption could represent the primary mechanism that leads to hypercalciuria (6,7,9,10).The intrinsic mechanisms that regulate the coordinated sequence of osteoclastogenesis and osteoblastogenesis during bone remodeling are not completely understood. In patients with chronic kidney disease mineral bone disorder (CKD-MBD), we have shown that, at a bone level, cytokines such as IL-1β and TNF-α act in synergism, stimulating bone resorption and inhibiting bone formation, whereas TGF-β and basic fibroblast growth factor (bFGF) present anabolic effects (17).The interaction between bone formation and resorption has been further elucidated by the characterization of osteoprotegerin (OPG) and the receptor activator of NF-κB ligand (RANKL) (18). RANKL plays a central role in osteoclast differentiation and can be inactivated by OPG. Recently, the bone expression of OPG and RANKL system was evaluated by means of an effective immunohistochemistry technique that we developed on the basis of a quick decalcification of bone sections embedded in methylmetacrylate (19); however, there have been no data concerning the role of cytokines in bone tissue of patients who have hypercalciuria and present with normal renal function. This study aimed to evaluate the expression of cytokines that are involved in either bone formation or resorption, such as TGF-β, bFGF, OPG, RANKL, and IL-1α, in bone biopsy material of IH stone-forming patients.     

Balo’s concentric sclerosis: Value of magnetic resonance imaging in diagnosis

We report two cases of Balo’s concentric sclerosis that demonstrate the typical magnetic resonance imaging (MRI) findings of concentric rings of demyelination involving the superficial and deep white matter and sparing the cortex. In both cases biopsy was not performed as MRI findings and multi-mode evoked potential studies were consistent with demyelinating illness. The theories regarding the pathogenesis of this peculiar appearance are briefly reviewed.     

HPLC-MS analysis of Schisandra lignans and their metabolites in Caco-2 cell monolayer and rat everted gut sac models and in rat plasma

The absorption profiles of Schisandra chinensis were evaluated using the human Caco-2 cell monolayer and rat everted gut sac models, as well as in rat plasma. By analyzing the chromatographic and MSⁿ characteristics of individual peak acquired by HPLC-DAD-APCI-MSⁿ determination, thirteen lignans were identified as the major in vitro absorbable components of the Schisandra extract. Most of these compounds were also detected and identified in rat plasma after an oral administration of the Schisandra extract, except for angeloyl(tigloyl)gomisin H and angeloyl(tigloyl)gomisin Q, whose structures possess an ester group at the cyclooctadiene ring. In addition, four metabolites, corresponding to the hydroxylation and demethylation products of schisandrin and the hydrolysis derivative of angeloyl(tigloyl)gomisin Q, were tentatively identified. The results demonstrate that Schisandra lignans are the major absorbable components of this crude drug, and hydroxylation, demethylation and hydrolysis are important metabolic transformations of the absorbable lignans.     

Determination of the DDE and PCB contents of peregrine Falcon eggs: A comparison of whole egg measurements and estimates derived from eggshell membranes

A method using eggshell membranes to determine egg content levels of DDE and polychlorobiphenyls (PCBs), two of the most ubiquitous environmental contaminants, has been validated. A comparison was made between the residue levels determined from the egg contents of 40 Peregrine Falcon (Falco peregrinus) eggs and from hexanesoluble extracts of the dried eggshell membranes. The results confirm the use of museum eggshells for estimations of DDE and PCB levels of the original egg contents. This method should be valid for other lipophilic compounds. The data generated are of use not only to determine the records of past contamination, but may be expected to provide useful information on patterns of contamination encountered in different geographical areas. The membrane extraction technique allows pollutant levels to be measured without removing viable material from endangered species.     

Apoptosis and proliferation under conditions of deoxynucleotide pool imbalance in liver of folate/methyl deficient rats

Weanling male F344 rats were fed either a semi-purified diet low in methionine and lacking in choline and folic acid (folate/methyl deficient) or a supplemented control diet for periods of 2, 5, 7 days, 3 weeks, and 9 weeks. Two days after initiating the folate/methyl deficient diet in weanling F344 rats, the incidence of apoptotic bodies, identified by in situ end-labeling of 3'-OH DNA strand breaks, was significantly increased in liver sections from the deficient rats. Apoptotic cell death was confirmed biochemically by an increase in nuclear Ca2+/Mg2+-dependent endonuclease activity that paralleled the increase in apoptotic bodies over the 9-week feeding period. There was no morphologic evidence of necrotic foci or necrosis-associated inflammatory response over the 9-week period. Confirming that cell turnover is chronically elevated in this model, the increase in apoptotic rate was accompanied by a sustained increase in the mitotic index (MI). The DNA repair-associated enzyme, poly(ADPribose) polymerase (PARP), was similarly elevated and was associated with significant decreases in the substrate for ADPribose polymer synthesis, nicotinamide adenine dinucleotide (NAD). Because folate metabolites are essential for de novo purine and thymidine biosynthesis, prolonged deficiency in folic acid can induce an imbalance in the deoxynucleotide precursors for DNA replication/repair and negatively affect the fidelity of DNA synthesis. Using an HPLC method, hepatic deoxyuridine triphosphate (dUTP) levels were increased at 3 and 9 weeks after initiation of the deficient diet and levels of thymidine triphosphate (dTTP) were reduced. An increase in dUTP/ dTTP ratio is consistent with a block in folate-dependent de novo thymidylate biosynthesis and may predispose to uracil misincorporation and DNA repair-related DNA strand breaks.      

Selective estrogen receptor modulators in chronic renal failure

BACKGROUND: In addition to renal osteodystrophy, postmenopausal women on dialysis could be at risk of osteoporosis. Hormone replacement therapy (HRT) could have beneficial effects as well as potentially serious risks, especially in uremic women, due to the pharmacokinetics of estradiol in renal failure. Therapeutic alternatives, such as the selective estrogen receptor modulators (SERMs), have shown the benefits of estrogen on bone and serum lipid levels, without its adverse effects on the breast and endometrium, in nonuremic women. METHODS: Recent data on the effect of the SERM raloxifene in bone and lipid metabolism in osteoporotic postmenopausal women on dialysis is reviewed. Since the estrogen receptor (ER) gene has been suggested as a candidate marker for osteoporosis, we investigated whether ER polymorphism could have predicted the BMD response to raloxifene. RESULTS: Hemodialyzed women on raloxifene demonstrated increased trabecular bone mineral density (BMD) and decreased bone resorption markers. Similarly, LDL-cholesterol values dropped significantly. ER gene polymorphism analysis of baseline BMD parameters did not differ between PP/xx or Pp/Xx groups. Nevertheless, patients on raloxifene with PP/xx genotypes, but not those with Pp/Xx, showed a higher trabecular BMD after one year on treatment, suggesting that homozygous women for P or x alleles of the ER have a better BMD response to raloxifene. CONCLUSION: Raloxifene and, most likely, other SERMs, could represent a good alternative to HRT in postmenopausal uremic women.