Melatonin, a pineal secretory product with antioxidant properties, protects against cisplatin-induced nephrotoxicity in rats

In an attempt to define the role of the pineal secretory melatonin and an analogue, 6-hydroxymelatonin (6-OHM), in limiting oxidative stress, the present study investigated the cisplatin (CP)-induced alteration in the renal antioxidant system and nephroprotection with the two indolamines. Melatonin (5 mg/kg), 6-OHM (5 mg/kg), or an equal volume of saline were administered intraperitoneally (i.p.) to male Sprague Dawley rats 30 min prior to an i.p. injection of CP (7 mg/kg). After CP treatment, the animals each received indolamine or saline every day and were sacrificed 3 or 5 days later and plasma as well as kidney were collected. Both plasma creatinine and blood urea nitrogen increased significantly following CP administration alone; these values decreased significantly with melatonin co-treatment of CP-treated rats. In the kidney, CP decreased the levels of GSH (reduced glutathione)/GSSG (oxidized glutathione) ratio, an index directly related to oxidative stress. When animals were treated with melatonin, the reduction in the GSH/GSSG ratio was prevented. Treatment of CP-enhanced lipid peroxidation in the kidney was again prevented in animals treated with melatonin. The activity of the antioxidant enzyme, glutathione peroxidase (GSH-Px), decreased as a result of CP administration, which was restored to control levels with melatonin co-treatment. Upon histological analysis, damage to the proximal tubular cells was seen in the kidneys of CP-treated rats; these changes were prevented by melatonin treatment. 6-OHM has been shown to have some antioxidative capacity, however, the protective effects of 6-OHM against CP-induced nephrotoxicity were less than those of melatonin. The residual platinum concentration in the kidney of melatonin co-treated rats was significantly lower than that of rats treated with CP alone. It is concluded that administration of CP imposes a severe oxidative stress to renal tissue and melatonin confers protection against the oxidative damage associated with CP. This mechanism may be reasonably attributed to its radical scavenging activity, to its GSH-Px activating property, and/or to its regulatory activity for renal function.     

Crystal structures of two tropinone reductases: Different reaction stereospecificities in the same protein fold

A pair of tropinone reductases (TRs) share 64% of the same amino acid residues and belong to the short-chain dehydrogenase/reductase family. In the synthesis of tropane alkaloids in several medicinal plants, the TRs reduce a carbonyl group of an alkaloid intermediate, tropinone, to hydroxy groups with different diastereomeric configurations. To clarify the structural basis for their different reaction stereospecificities, we determined the crystal structures of the two enzymes at 2.4- and 2.3-Å resolutions. The overall folding of the two enzymes was almost identical. The conservation was not confined within the core domains that are conserved within the protein family but extended outside the core domain where each family member has its characteristic structure. The binding sites for the cofactor and the positions of the active site residues were well conserved between the two TRs. The substrate binding site was composed mostly of hydrophobic amino acids in both TRs, but the presence of different charged residues conferred different electrostatic environments on the two enzymes. A modeling study indicated that these charged residues play a major role in controlling the binding orientation of tropinone within the substrate binding site, thereby determining the stereospecificity of the reaction product. The results obtained herein raise the possibility that in certain cases different stereospecificities can be acquired in enzymes by changing a few amino acid residues within substrate binding sites.     

Development of a simple serological method for diagnosing leptospirosis: a microcapsule agglutination test.

A passive microcapsule agglutination test for the diagnosis of leptospirosis was developed by utilizing chemically stable microcapsules instead of sheep erythrocytes. In the test, sonically disrupted antigens of leptospira were sensitized to microcapsules treated with glutaraldehyde. Compared with the microscopic agglutination test, the passive microcapsule agglutination test showed a relatively genus-specific tendency and a 4- to 32-fold-higher sensitivity. The sensitized microcapsule antigens were stable for at least 1 year. The microcapsules coupled with mixed antigens can be used as a serodiagnostic screening test for diseases caused by various types of leptospira. The test, which is very simple and reproducible and requiring no specific training, can be employed easily as a routine test in diagnostic laboratories.     

Pharmacogenetics of disease modifying anti-rheumatic drugs

There are large differences in the effectiveness of disease modifying anti-rheumatic drugs(DMARD) from one person to the next. Adverse drug reactions caused by DMARD can also occur to some patients, but do not occur to others. One possible cause of the differences in the effectiveness and adverse drug reactions is genetic variation in how individuals metabolize drugs. The Human Genome Project heralds new opportunities for using information about genetic variation to predict responses to drug therapies, called pharmacogenetics. Based on pharmacogenetics, tailor-made drug therapy is going to be realized. Our recent studies revealed the relationship between genetic polymorphisms of drug metabolizing enzymes and the efficacy of methotrexate or sulfasalazine in patients with rheumatoid arthritis, suggesting pharmacogenetics is applicable to the treatment of rheumatoid arthritis.     

Glucocorticoid receptor in patients with lupus nephritis: relationship between receptor levels in mononuclear leukocytes and effect of glucocorticoid therapy.

We investigated the clinical significance of glucocorticoid receptor determination in 20 patients with systemic lupus erythematosus (SLE) who afterwards developed nephrotic syndrome. Glucocorticoid receptor concentrations in mononuclear leukocytes (MNL) in these patients were comparable with those in both other patients with SLE and healthy persons. Improvement in urinary protein excretion and in disease activity, which was scored according to the SLE Disease Activity Index system of the University of Toronto, closely related to the glucocorticoid receptor concentrations in MNL isolated from the corresponding patients. In summary, glucocorticoid receptor determination in patients with lupus nephritis may be a predictive clue for assessing responsiveness to glucocorticoid therapy.     

Amyloid-β peptide activates cultured astrocytes: morphological alterations, cytokine induction and nitric oxide release

A common feature of many neurodegenerative disorders is an abundance of activated glial cells (astrocytes and microglia). In Alzheimer's disease (AD), activated astrocytes are in close apposition to and surrounding the amyloid plaques. The mechanisms by which the astrocytes become activated in AD and the consequences of reactive astrocytosis to disease progression are not known. We examined the possibility that the amyloid-β (Aβ) peptide, a major constituent of the amyloid plaque, could act as a stimulus leading to activation. We found that treatment of rat cortical astrocyte cultures with aggregated Aβ 1–42 peptide induces activation, as assessed by reactive morphological changes and upregulation of selective glial mRNA and proteins, such as the inflammatory cytokine interleukin-1β. Aβ also stimulates inducible nitric oxide synthase (iNOS) mRNA levels and nitric oxide (NO) release. Aβ 1–42, a major form of amyloid associated with neurotoxicity, activated astrocytes in a time- and dose-dependent manner, whereas a scrambled Aβ 1–42 sequence or Aβ 17–42 had little or no effect. We also determined that the Aβ activity can be found in a supernatant fraction containing soluble Aβ oligomers. Our data suggest that Aβ plays a role in the reactive astrocytosis of AD and that the inflammatory response induced upon glial activation is a critical component of the neurodegenerative process.     

Suppression of adjuvant-induced arthritic bone destruction by cyclooxygenase-2 selective agents with and without inhibitory potency against carbonic anhydrase II.

In vitro assays revealed that COX-2 inhibitors with CA II inhibitory potency suppressed both differentiation and activity of osteoclasts, whereas that without the potency reduced only osteoclast differentiation. However, all COX-2 inhibitors similarly suppressed bone destruction in adjuvant-induced arthritic rats, indicating that suppression of osteoclast differentiation is more effective than that of osteoclast activity for the treatment. INTRODUCTION: Cyclooxygenase (COX)-2 and carbonic anhydrase II (CA II) are known to play important roles in the differentiation of osteoclasts and the activity of mature osteoclasts, respectively. Because several COX-2 selective agents were recently found to possess an inhibitory potency against CA II, this study compared the bone sparing effects of COX-2 selective agents with and without the CA II inhibitory potency. MATERIALS AND METHODS: Osteoclast differentiation was determined by the mouse co-culture system of osteoblasts and bone marrow cells, and mature osteoclast activity was measured by the pit area on a dentine slice resorbed by osteoclasts generated and isolated from bone marrow cells. In vivo effects on arthritic bone destruction were determined by radiological and histological analyses of hind-paws of adjuvant-induced arthritic (AIA) rats. RESULTS: CA II was expressed predominantly in mature osteoclasts, but not in the precursors. CA II activity was inhibited by sulfonamide-type COX-2 selective agents celecoxib and JTE-522 similarly to a CA II inhibitor acetazolamide, but not by a methylsulfone-type COX-2 inhibitor rofecoxib. In vitro assays clearly revealed that celecoxib and JTE-522 suppressed both differentiation and activity of osteoclasts, whereas rofecoxib and acetazolamide suppressed only osteoclast differentiation and activation, respectively. However, bone destruction in AIA rats was potently and similarly suppressed by all COX-2 selective agents whether with or without CA II inhibitory potency, although only moderately by acetazolamide. CONCLUSIONS: Suppression of osteoclast differentiation by COX-2 inhibition is more effective than suppression of mature osteoclast activity by CA II inhibition for the treatment of arthritic bone destruction.