Adduct formation between oxanine and amine derivatives

Oxanine (Oxa) is a major guanine lesion produced by nitric oxide (NO) under aerobic conditions. To elucidate the genotoxic mechanism of Oxa, this lesion was site-specifically incorporated into an oligonucleotide and allowed to react with cellular amines. Analysis of the reaction product revealed that Oxa formed adducts with spermidine and lysine, suggesting a novel genotoxic mechanism associated with NO-induced DNA damage.

Angiotensin-converting enzyme gene polymorphism as a potent risk factor for developing microalbuminuria in Japanese patients with type 2 diabetes mellitus: a 9-year follow-up study

To clarify the risk factors for developing microalbuminuria in patients with type 2 diabetes mellitus, a longitudinal observational study was performed. Fifty patients with normoalbuminuria were recruited and treated conventionally for 9 years. Polymorphisms of the angiotensin-converting enzyme (ACE) gene and the angiotensinogen M235T polymorphism were examined. During the study period, 12 of the 50 patients developed microalbuminuria; no patients progressed to macroalbuminuria. Multiple logistic regression analysis was performed using age, duration of diabetes, body mass index, haemoglobin A1c' blood pressure, serum lipid profile and genetic polymorphisms as independent variables and development of microalbuminuria as the dependent variable. The D allele of the ACE gene was an independent and significant variable. We conclude that the ACE gene D allele polymorphism is a potent risk factor for developing microalbuminuria in type 2 diabetic patients.

Accumulation of oligoclonal T cells in the infiltrating lymphocytes in oral lichen planus

BACKGROUND

Identification of a disease-specific and possibly pathogenic T-cell receptor (TCR) in oral lichen planus (OLP) is one of the most important steps to reveal the pathogenic antigen recognized by the T cells and thereby elucidate the pathogenesis and etiology of OLP.

METHODS

In buccal mucosa biopsy specimens and peripheral blood mononuclear cells (PBMC) from seven patients with OLP, the TCR V beta gene usage was examined by polymerase chain reaction-based and single-strand conformation polymorphism analyses.

RESULTS

The V beta families expressed in the biopsy specimens were markedly heterogeneous, but they were restricted in comparison to those observed in the PBMC. The V beta families predominantly expressed in the biopsy specimens in comparison with the PBMC were still heterogeneous in individual patients and differed from patient to patient; however, V beta 2, V beta 6, and V beta 19 were commonly predominant in the biopsy specimens from more than half of the patients. Among the V beta families predominantly expressed in the biopsy specimens, the accumulation of T-cell clonotypes was observed in the majority of the V beta families including V beta 6 and V beta 19; however, it was not observed in the minority of the V beta families including V beta 2.

CONCLUSIONS

These results suggest that unique T-cell populations bearing V beta 2, V beta 6, or V beta 19 gene products tend to expand in OLP lesions as a consequence of in situ stimulation with a restricted epitope of either a nominal antigen on the MHC molecule for the majority of the V beta families, even if only in minor populations, or of a common superantigen for the minority of the V beta families.

Core structure in roselipins essential for eliciting inhibitory activity against diacylglycerol acyltransferase

Fungal roselipins, discovered as inhibitors of diacylglycerol acyltransferase (DGAT), consist of three parts; highly methylated C20 fatty acid, mannose and arabinitol. Demannosyl and/or dearabinitoyl roselipins were prepared chemically or enzymatically. Demannnosyl roselipins conserved the DGAT inhibitory activity, but the others lost the activity, indicating that the arabinitoyl fatty acid core is essential for eliciting the activity.

Bacterial fimbriae and their peptides activate human gingival epithelial cells through Toll-like receptor 2

Gingival epithelial cells are a central component of the barrier between oral microflora and internal tissues. Host responses to periodontopathic bacteria and surface components containing fimbriae are thought to be important in the development and progression of periodontal diseases. To elucidate this mechanism, we established immortalized human gingival epithelial cells (HGEC) that were transfected with human papillomavirus. HGEC predominantly expressed Toll-like receptor (TLR) 2, but not TLR4 or CD14. They also induced interleukin-8 (IL-8) production when stimulated with Porphyromonas gingivalis fimbriae and Staphylococcus aureus peptidoglycan, but not Escherichia coli-type synthetic lipid A. Furthermore, an active synthetic peptide composed of residues 69 to 73 (ALTTE) of the fimbrial subunit protein, derived from P. gingivalis and similar to a common component of cell wall peptidoglycans in parasitic bacteria, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), significantly induced IL-8 production and NF-kappaB activation in HGEC, and these cytokine-producing activities were augmented by a complex of soluble CD14 and lipopolysaccharide-binding protein (LBP). IL-8 production in HGEC stimulated with these bacterial components was clearly inhibited by mouse monoclonal antibody to human TLR2. These findings suggest that P. gingivalis fimbrial protein and its active peptide are capable of activating HGEC through TLR2.

Combined primary aldosteronism and preclinical Cushing's syndrome: an unusual case presentation of adrenal adenoma

A 55-year-old woman was referred to our institution for evaluation of elevated plasma creatine phosphokinase, hypokalemia and hypertension. Her chief complaints were muscle weakness and polyuria. A left adrenal mass, 4 cm in diameter, was noted on computed tomography. Hormonal assessment demonstrated markedly elevated plasma aldosterone concentration, markedly low plasma renin activity, an abnormal diurnal variation in serum cortisol levels, suppressed baseline plasma adrenocorticotrophic hormone, and non-suppression of serum cortisol by dexamethasone suppression test. She showed no symptoms or signs suggestive of Cushing's syndrome. Adrenal scintigraphy with 131I-6-beta-iodomethyl-norcholesterol showed uptake on the left adrenal and inhibition of the contralateral adrenal gland. She was diagnosed with combined primary aldosteronism and preclinical Cushing's syndrome. Cases of combined primary aldosteronism and preclinical Cushing's syndrome are extremely rare. In patients with large aldosterone-producing adenoma, contralateral adrenal insufficiency should be anticipated after the removal of the tumor.

Metabolic activation of 1alpha-hydroxyvitamin D3 in human liver microsomes

1. 1Alpha-hydroxyvitamin D3 (1alpha-OH-D3) is a synthetic prodrug of the active form of vitamin D3, and requires the hydroxylation at the C-25 position before eliciting its biological activity. 2. 25-Hydroxylation activities for 1alpha-OH-D3 were present in both microsomal and mitochondrial fractions of human liver. 3. To determine the P450 enzyme(s) involved in microsomal 25-hydroxylation, 14 P450s (CYP1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9-Arg, 2C9-Cys, 2C19, 2D6-Val, 2D6-Met, 2E1, 3A4, 4A11) were tested for their 25-hydroxylation activity of 1alpha-OH-D3. None catalysed the 25-hydroxylation reaction. 4. 1Alpha-OH-D3 in a high concentration (2.5 ng ml(-1)) showed small but significant inhibition of the catalytic activities of CYP2C8, 2C9-Cys, 2C19, 2D6-Val and 2E1 for their typical substrates. However, 1alpha-OH-D3 in a clinically used low concentration will not significantly affect drug metabolism catalysed by the 14 P450s tested. 5. In summary, the 25-hydroxylation activity of 1alpha-OH-D3 that localizes in the microsomal fraction appears to be attributable to a cytochrome P450 other than the microsomal forms tested in this study.

Polymorphism of the polyalanine tract of thyroid transcription factor-2 gene in patients with thyroid dysgenesis

OBJECTIVE

One of the thyroid-specific transcription factors, thyroid transcription factor-2 (TTF-2), performs a crucial role in the development of the thyroid gland. We performed genetic analysis of the TITF2 gene (encoding TTF-2) in patients with thyroid dysgenesis.

METHODS

By direct sequencing of the PCR products of TITF2, we screened the genomic DNA from 46 patients with thyroid dysgenesis (five had agenesis, six had hypoplasia, 15 had ectopy, and 20 were undetermined). We also studied the transcriptional activities of TITF2 by co-expressing the luciferase gene directed by the human thyroglobulin gene promoter.

RESULTS

Human TITF2 consists of a forkhead domain, a polyalanine tract, and unique C-terminal residues. In one of the patients with an ectopic sublingual thyroid, we found a polyalanine tract of 11 alanine residues on one chromosome instead of the 14 alanine residues found in normal controls. In one patient with hypoplasia, the polyalanine tract consisted of 12 heterozygous alanine residues. The reduced polyalanine tracts were not detected in 101 normal individuals. However, the expression study showed that the transcriptional activities of TITF2 with reduced polyalanine-tract lengths were equal to that of TITF2 with an unreduced polyalanine tract.

CONCLUSION

These results suggest that the polymorphism of the polyalanine tract of TITF2 is not a frequent cause of developmental defects of the human thyroid gland.

Recurrent pyogenic vertebral osteomyelitis associated with type 2 diabetes mellitus

We report a case of recurrent pyogenic vertebral osteomyelitis associated with type 2 diabetes mellitus. A 51-year-old male was admitted to our hospital because of lumbago and general fatigue, with multiple ulcers on the soles of his feet. Staphylococcus aureus was isolated from peripheral blood and the foot ulcers, and 67Gallium scintigram showed abnormal isotope uptake, accumulated at the lower thoracic spine. Antibiotics were administered and the patient underwent intensive insulin therapy. Magnetic resonance imaging (MRI), performed after the levels of C-reactive protein decreased to 0.0 mg/dl, indicated old inflammatory changes at the Th8-Th9 spine and antibiotics were stopped. Unexpectedly, 8 days later the patient complained of lumbago with fever again, and MRI showed acute inflammatory changes at the same lesion site. This case report suggests that it is important for complementary antibiotic therapy to continue after signs of inflammation have disappeared in cases of pyogenic vertebral osteomyelitis.

Role of blood pressure in the progression of microalbuminuria in elderly Japanese type 2 diabetic patients: a 7-year follow-up study

This 7-year retrospective longitudinal study was carried out in order to clarify the clinical features of elderly type 2 diabetic patients with microalbuminuria. Elderly Japanese type 2 diabetic patients (n = 22; age 50 - 73 years) with microalbuminuria were studied retrospectively. Patients whose urinary albumin excretion rate (UAER) decreased 7 years were considered 'nonprogressors' (n = 8) whereas those whose UAER increased were considered 'progressors' (n = 14). The mean 7-year level of glycosylated haemoglobin (HbA1c) did not differ significantly between non-progressors and progressors but the mean 7-year blood pressure (BP) of progressors (101 +/- 8 mmHg) was significantly higher than that of non-progressors (92 +/- 7 mmHg). In progressors who received no anti-hypertensive drugs, systolic BP was above the BP goal of 130/85 mmHg but mean BP and diastolic BP were below this goal. The results are consistent with the view that hypertension affects the progression of microalbuminuria; raised systolic BP may be a factor in this progression in elderly type 2 diabetic patients.

Oxidation of thymine to 5-formyluracil in DNA promotes misincorporation of dGMP and subsequent elongation of a mismatched primer terminus by DNA polymerase

5-Formyluracil (fU) is a major oxidative thymine lesion generated by ionizing radiation and reactive oxygen species. In the present study, we have assessed the influence of fU on DNA replication to elucidate its genotoxic potential. Oligonucleotide templates containing fU at defined sites were replicated in vitro by Escherichia coli DNA polymerase I Klenow fragment deficient in 3'-5'-exonuclease. Gel electrophoretic analysis of the reaction products showed that fU constituted very weak replication blocks to DNA synthesis, suggesting a weak to negligible cytotoxic effect of this lesion. However, primer extension assays with a single dNTP revealed that fU directed incorporation of not only correct dAMP but also incorrect dGMP, although much less efficiently. No incorporation of dCMP and dTMP was observed. When fU was substituted for T in templates, the incorporation efficiency of dAMP (f(A) = V(max)/K(m)) decreased to (1/4) to (1/2), depending on the nearest neighbor base pair, and that of dGMP (f(G)) increased 1.1-5.6-fold. Thus, the increase in the replication error frequency (f(G)/f(A) for fU versus T) was 3.1-14.3-fold. The misincorporation rate of dGMP opposite fU (pK(a) = 8.6) but not T (pK(a) = 10.0) increased with pH (7.2-8.6) of the reaction mixture, indicating the participation of the ionized (or enolate) form of fU in the mispairing with G. The resulting mismatched fU:G primer terminus was more efficiently extended than the T:G terminus (8.2-11.3-fold). These results show that when T is oxidized to fU in DNA, fU promotes both misincorporation of dGMP at this site and subsequent elongation of the mismatched primer, hence potentially mutagenic.

[Development and evaluation of a QOL questionnaire for elderly subject living in a community]

A comprehensive, basic and simple QOL questionnaire for elderly subjects living in a community was developed, and its validity and reliability were examined. The subjects were 2944 individuals of 65 years or older living in 5 areas of metropolitan Tokyo and in a town of Aichi Prefecture. The QOL questionnaire with 19 questions was developed based on the component of QOL by Lawton and concept of QOL by Koyano. The questionnaire consisted of 6 subscales (daily activity, satisfaction with health, satisfaction with human support, satisfaction with economic state, symptom of depression and positive mental attitude). Factor analysis revealed that the 19 questions could be clearly separated into 6 components in Tokyo and Aichi districts with total variances of 70.8% and 78.4%, respectively. Scores of daily activity and positive mental attitude were significantly lower with older subjects in both men and women. However, scores for other subscales did not differ with age. Primary factors which are considered to affect QOL were compared with the 6 QOL subscales of this study. Being an outpatient had a significant relation to daily activity and satisfaction with health, presence of a spouse to satisfaction with human support, depressive state, positive mental attitude and possession of ones own room to satisfaction with economical state, and belief in religion to positive mental attitude. The results suggest that the present questionnaire include the basic components necessary for evaluation of QOL in elderly subjects living in a community. Further research is required to examine the validity of this questionnaire with correction of questions.

Phantom evaluation of scatter and attenuation correction in thallium-201/technetium-99m acquisition in myocardial perfusion single-photon emission computed tomography

PURPOSE

This phantom study was carried out to evaluate the usefulness of scatter correction combined with transmission-based attenuation correction in separate and simultaneous 201Tl/99mTc myocardial SPECT.

METHODS

An anthropomorphic torso phantom was used in this study. We used the triple-energy-window (TEW) method for scatter correction and transmission computed tomography (TCT) images for attenuation correction. Images without corrections (UC) and images with corrections (SAC) for scatter and attenuation were reconstructed for the evaluation.

RESULTS

The differences in defect size between 99mTc and 201Tl UC images led to interpretation errors in separate (separate protocol) and simultaneous dual-isotope studies (simultaneous protocol). These errors were more prominent in the infero-posterior wall in the simultaneous protocol. Improvement for overestimation in object size and underestimation in defect contrast was visually obtained, and increased contrast was also shown by the myocardium-to-defect count (MD) ratios on SAC images in the separate and simultaneous protocols. However, 201Tl SAC images in the simultaneous protocol still had less defect contrast than the corresponding 201Tl SAC images in the separate protocol.

CONCLUSIONS

From the results of our phantom experiment, separate rest 201Tl/stress 99mTc-sestamibi acquisitions may be recommended in clinical practice. Further clinical and phantom studies will be needed to validate the method using scatter correction combined with transmission-based attenuation correction.

Diagnostic accuracy of simultaneous acquisition of transmission and emission data with technetium-99m transmission source on thallium-201 myocardial SPECT

PURPOSE

This study evaluates not only the clinical usefulness but also the problems in attenuation correction for thallium-201 (Tl-201) myocardial SPECT by means of simultaneous transmission and emission data acquisition in the detection of coronary artery disease (CAD).

METHODS

A three-detector SPECT system equipped with a Tc-99m line source and fan-beam collimators was used for simultaneous transmission and emission data acquisition for Tl-201 myocardial SPECT in 73 patients (18 patients for normal database and 55 patients for the evaluation of diagnostic accuracy). Attenuation-corrected (AC) images and non-attenuation-corrected (NC) images were reconstructed with an iterative maximum-likelihood estimation-corrected (ML-EM) algorithm. Both sets of images were reoriented into the short axis. Normal database polar maps were constructed from the AC and NC images for quantitative analysis.

RESULTS

There was a significant difference in specificity between NC and AC images in the RCA territory and those in specificity and accuracy in the LCX territory. There was no significant difference in sensitivity found between NC and AC images in either territory, but sensitivity in both territories tended to decrease with attenuation correction. In the LAD territory, there were various changes in sensitivity and specificity observed with attenuation correction in cases with each quantitative criterion.

CONCLUSIONS

Diagnostic performance of significant stenosis in the RCA and LCX territories quantitatively improved with attenuation correction because of an increase in specificity, but no significant improvement in diagnostic performance was obtained in the LAD territory with attenuation correction. We recommend combined interpretation of AC and NC images and careful evaluation of any SPECT image by means of transmission computed tomography.

Homeobox protein Hex induces SMemb/nonmuscle myosin heavy chain-B gene expression through the cAMP-responsive element

Recent studies have shown that the homeobox gene Hex plays an important role in inducing differentiation of vascular endothelial cells. In this study, we examined the expression of Hex in vascular smooth muscle cells (VSMCs) in vitro and in vivo. Immunohistochemistry showed a marked induction of Hex protein in neointimal VSMCs after balloon injury in rat aorta. Western and reverse transcriptase-polymerase chain reaction analyses demonstrated that Hex was abundantly expressed in cultured VSMCs, whereas it was undetectable in other cell types or in normal aorta. The expression pattern of Hex was similar to that of SMemb/NMHC-B, a nonmuscle isoform of myosin heavy chain that we have previously reported to be a molecular marker of dedifferentiated VSMCs. We next examined the role of Hex in SMemb gene transcription. Promoter analysis demonstrated that the sequence identical to consensus cAMP-responsive element (CRE) located at -481 of the SMemb promoter was critical for Hex responsiveness. Mutant Hex expression vector, which lacks the homeodomain, failed to stimulate SMemb gene transcription, suggesting the requirement of the homeodomain for its transactivation. Elecrophoretic mobility shift assay showed that Hex binds to a consensus binding sequence for homeobox proteins, but not to CRE. Cotransfection of protein kinase A expression vector increased the ability of Hex to stimulate SMemb promoter activity in a CRE-dependent manner. Overexpression of CRE binding protein (CREB), but not Mut-CREB which contains mutation at Ser133, strongly activated Hex-induced SMemb promoter activity. These results suggest that Hex mediates transcriptional induction of the SMemb/NMHC-B gene via its homeodomain, and Hex can function as a transcriptional modulator of CRE-dependent transcription in VSMCs.

Mutations in the TATA-binding protein, affecting transcriptional activation, show synthetic lethality with the TAF145 gene lacking the TAF N-terminal domain in Saccharomyces cerevisiae

The general transcription factor TFIID, which is composed of the TATA box-binding protein (TBP) and a set of TBP-associated factors (TAFs), is crucial for both basal and regulated transcription by RNA polymerase II. The N-terminal small segment of yeast TAF145 (yTAF145) binds to TBP and thereby inhibits TBP function. To understand the physiological role of this inhibitory domain, which is designated as TAND (TAF N-terminal domain), we screened mutations, synthetically lethal with the TAF145 gene lacking TAND (taf145 Delta TAND), in Saccharomyces cerevisiae by exploiting a red/white colony-sectoring assay. Our screen yielded several recessive nsl (Delta TAND synthetic lethal) mutations, two of which, nsl1-1 and nsl1-2, define the same complementation group. The NSL1 gene was found to be identical to the SPT15 gene encoding TBP. Interestingly, both temperature-sensitive nsl1/spt15 alleles, which harbor the single amino acid substitutions, S118L and P65S, respectively, were defective in transcriptional activation in vivo. Several other previously characterized activation-deficient spt15 alleles also displayed synthetic lethal interactions with taf145 Delta TAND, indicating that TAND and TBP carry an overlapping but as yet unidentified function that is specifically required for transcriptional regulation.

Metabolism of 26,27-hexafluoro-1 alpha,25-dihydroxyvitamin D3 and 26,27-hexafluoro-1 alpha,23(S)25-trihydroxyvitamin D3 in ROS17/2.8 cells transfected with a plasmid expressing CYP24

1. To clarify the possibility that the metabolism of 26,27-hexafluoro-1 alpha,25-dihydroxyvitamin D3 [F6-1,25(OH)2D3] to 26,27-hexafluoro-1 alpha,23(S),25-trihydroxyvitamin D3 [F6-1,23,25(OH)3D3 and that of F6-1,23,25(OH)3D3 to 26,27-hexafluoro-23-oxo-1 alpha,25-dihydroxyvitamin D3 [F6-23-oxo-1,25(OH)2D3] are catalysed by 25-hydroxyvitamin D3 24-hydroxylase (CYP24), ROS17/2.8 cells transfected with a plasmid expressing CYP24 [pSVL-CYP24(+)] and a corresponding blank plasmid [pSLV-CYP24R(-)] were used. 2. Incubation of [1 beta-3H]-F6-1,25(OH)2D3 for 2 and 5 days with ROS17/2.8 cells transfected with pSVL-CYP24(+) generated a metabolite that co-migrated with authentic F6-1,23,25(OH)3D3 in both normal phase and reversed-phase HPLC systems. 3. Incubation of [1 beta-3H]-F6-1,23,25(OH)3D3 for 5 days with pSVL-CYP24(+)- transfected ROS 17/2.8 cells generated a metabolite that co-migrated with authentic F6-23-oxo-1,25(OH)2D3. In contrast, the metabolites F6-1,23,25(OH)3D3 or F6-23-oxo-1,25(OH)2D3 were not generated in the cells transfected with pSVL-CYP24R(-). 4. The results indicate that CYP24 catalyses the conversion of F6-1,25(OH)2D3 to F6-1,23,25(OH)3D3 and that of F6-1,23,25(OH)3D3 to F6-23-oxo-1,25(OH)2D3.

Dual metabolic pathway of 25-hydroxyvitamin D3 catalyzed by human CYP24

Human 25-hydroxyvitamin D3 (25(OH)D3) 24-hydroxylase (CYP24) cDNA was expressed in Escherichia coli, and its enzymatic and spectral properties were revealed. The reconstituted system containing the membrane fraction prepared from recombinant E. coli cells, adrenodoxin and adrenodoxin reductase was examined for the metabolism of 25(OH)D3, 1alpha,25(OH)2D3 and their related compounds. Human CYP24 demonstrated a remarkable metabolism consisting of both C-23 and C-24 hydroxylation pathways towards both 25(OH)D3 and 1alpha,25(OH)2D3, whereas rat CYP24 showed almost no C-23 hydroxylation pathway [Sakaki, T. Sawada, N. Nonaka, Y. Ohyama, Y. & Inouye, K. (1999) Eur. J. Biochem. 262, 43-48]. HPLC analysis and mass spectrometric analysis revealed that human CYP24 catalyzed all the steps of the C-23 hydroxylation pathway from 25(OH)D3 via 23S, 25(OH)2D3, 23S,25,26(OH)3D3 and 25(OH)D3-26,23-lactol to 25(OH)D3-26, 23-lactone in addition to the C-24 hydroxylation pathway from 25(OH)D3 via 24R,25(OH)2D3, 24-oxo-25(OH)D3, 24-oxo-23S,25(OH)2D3 to 24,25,26,27-tetranor-23(OH)D3. On 1alpha,25(OH)2D3 metabolism, similar results were observed. These results strongly suggest that the single enzyme human CYP24 is greatly responsible for the metabolism of both 25(OH)D3 and 1alpha,25(OH)2D3. We also succeeded in the coexpression of CYP24, adrenodoxin and NADPH-adrenodoxin reductase in E. coli. Addition of 25(OH)D3 to the recombinant E. coli cell culture yielded most of the metabolites in both the C-23 and C-24 hydroxylation pathways. Thus, the E. coli expression system for human CYP24 appears quite useful in predicting the metabolism of vitamin D analogs used as drugs.

[Chorioretinal blood flow changes following acupuncture between thumb and forefinger]

PURPOSE

To evaluate the effects of acupuncture stimuli on general circulation and chorioretinal blood flow changes, and to determine the duration of effect and the learning effect.

OBJECTS AND METHODS

Twelve healthy young volunteers were divided into two groups. One had no experience of acupuncture (Non-Experience group); the other had experience of acupuncture (Experience group). Hegu (LI 4) between thumb and forefinger was acupunctured. Chorioretinal blood flow was measured via Heidelberg retina flowmeter before, during, and after acupuncture stimuli.

RESULTS

In both groups, chorioretinal blood flow increased significantly during stimuli, with continuous bradycardia. The Experience group showed greater changes than the Non-Experience group.

CONCLUSIONS

Chorioretinal blood flow was increased through relative parasympathetic reaction by stimulating an acupuncture point. Acupuncture is a promising adjunctive therapy for ischemic ocular diseases.

In vivo klotho gene delivery protects against endothelial dysfunction in multiple risk factor syndrome

The klotho gene, originally identified by insertional mutagenesis in mice, suppresses multiple aging phenotypes (e.g., arteriosclerosis, pulmonary emphysema, osteoporosis, infertility, and short life span). We have previously shown that mice heterozygous for a defect in the klotho gene upon parabiosis with wild-type mice show improved endothelial function, suggesting that the klotho gene product protects against endothelial dysfunction. In the present study, using the Otsuka Long-Evans Tokushima Fatty (OLETF) rat which demonstrates multiple atherogenic risk factors (e.g., hypertension, obesity, severe hyperglycemia, and hypertriglyceridemia) and is thus considered an experimental animal model of atherosclerotic disease, we show that adenovirus-mediated klotho gene delivery can (1) ameliorate vascular endothelial dysfunction, (2) increase nitric oxide production, (3) reduce elevated blood pressure, and (4) prevent medial hypertrophy and perivascular fibrosis. Based on these findings, klotho gene delivery improves endothelial dysfunction through a pathway involving nitric oxide, and is involved in modulating vascular function (e.g., hypertension and vascular remodeling). Our findings establish the basis for the therapeutic potential of klotho gene delivery in atherosclerotic disease.

Comparison of substrate specificities of Escherichia coli endonuclease III and its mouse homologue (mNTH1) using defined oligonucleotide substrates

Escherichia coli endonuclease III (Endo III) and its eukaryotic homologues are major repair enzymes for pyrimidine lesions formed by reactive oxygen species and ionizing radiation. In the present study, the activities of Endo III and its mouse homologue (mNTH1) have been compared using defined oligonucleotide substrates containing a urea residue (UR), two cis-thymine glycol (TG) diastereoisomers, 5, 6-dihydrothymine (DHT), and 5-hydroxyuracil (HOU). The substrates were incubated with Endo III and mNTH1, and their activities were compared based on the product analysis by gel electrophoresis. Endo III recognized all base lesions tested, but the activity for DHT was extremely lower than other substrates. In contrast, albeit some preference of UR, mNTH1 showed essentially comparable activities for all substrates including DHT. Comparison of the enzymatic parameters for cis-TG and DHT revealed that large decreases in the affinity (K(m), 27-fold) and k(cat) (11-fold) relative to cis-TG made DHT an very poor substrate for Endo III. mNTH1 had comparable affinities and k(cat) for both cis-TG and DHT, though turnover (k(cat)) of mNTH1 was notably slower than Endo III. In view of the reaction mechanism, the paired base effect on the damage recognition by the two enzymes was also examined. The activities of Endo III for UR and HOU were paired base-independent, but those for cis-TG and DHT were significantly enhanced when paired with G. With mNTH1, the paired base effect was evident only for DHT. The variations of the repair activity with paired bases and enzymes are discussed in relation to the base flipping mechanism suggested for base excision repair enzymes.

Characterization of S818L mutation in HERG C-terminus in LQT2. Modification of activation-deactivation gating properties

We examined the mechanism(s) for HERG channel dysfunction in an S818L mutation in the HERG C-terminus using the heterologous expression system in Xenopus oocytes. Injection of S818L cRNA alone did not produce expressed currents. Coinjection of an equal amount of S818L cRNA with wild-type (WT) cRNA into oocytes did not exhibit apparent dominant-negative suppression. However, coinjection of excess amounts of S818L cRNAs with WT cRNA into oocytes decreased HERG current amplitudes and shifted the voltage dependence of activation to negative potentials, accelerated its activation and deactivation. The data suggest that S818L alone cannot form functional channels, whereas S818L subunits can, at least in part, coassemble with WT subunits to form heterotetrameric functional channels, and imply that the HERG C-terminus may contain a domain involving the activation-deactivation process of the channel. These findings may provide new insights into the structure-function relationships of the HERG C-terminus.

Decreased insulin production and increased insulin sensitivity in the klotho mutant mouse, a novel animal model for human aging

We have recently identified a novel gene, klotho (kl), which may suppress several aging phenotypes. A defect of kl gene expression in the mouse results in a syndrome resembling human aging, such as arteriosclerosis, skin atrophy, osteoporosis, and pulmonary emphysema. To determine whether mouse homozygotes for the kl mutation (kl/kl) show abnormal glucose metabolism, an oral glucose tolerance test (OGTT) was performed at 6 to 8 weeks of age. Blood glucose levels during the OGTT were significantly lower in kl/kl mice versus wild-type mice. The insulin content of the pancreas was significantly lower in kl/kl mice compared with wild-type mice. Decreased insulin production was also supported by Northern blot analysis showing lower levels of insulin mRNA in kl/kl mice. To examine how lower blood glucose levels may exist in kl/kl mice despite decreased insulin production, insulin tolerance tests (ITTs) were performed. The glucose decline following insulin injection was more severe in kl/kl mice versus wild-type mice, suggesting that insulin sensitivity was higher in kl/kl mice versus wild-type mice. In kl/kl mice, an augmented expression of GLUT4 in skeletal muscle was demonstrated by both Northern blot analysis and Western blot analysis. Thus, we conclude that insulin production is decreased and insulin sensitivity is increased in the klotho mouse, a novel animal model for human aging.

Recognition of formamidopyrimidine by Escherichia coli and mammalian thymine glycol glycosylases. Distinctive paired base effects and biological and mechanistic implications

The activity of prokaryotic and mammalian thymine glycol (Tg) glycosylases including Escherichia coli endonuclease III (Endo III) and endonuclease VIII (Endo VIII) and mouse Endo III homologue (mNth1) for formamidopyrimidine (Fapy) has been investigated using defined oligonucleotide substrates. 2, 6-Diamino-4-hydroxy-5-N-methylformamidopyrimidine, a methylated Fapy derived from guanine, was site specifically incorporated in the oligonucleotide. The substrates containing Fapy:N pairs (N = A, G, C, T) as well as a Tg:A pair, a physiological substrate of Endo III, Endo VIII, and mNth1, were treated by the enzymes and nicked products were quantified by gel electrophoresis. The activity of Endo III and Endo VIII for Fapy varied markedly depending on the paired base, being the highest with G (activity relative to Tg = 0. 55 (Endo III) and 0.41 (Endo VIII)) and the lowest with C (0.05 (Endo III) and 0.06 (Endo VIII)). In contrast, mNth1 recognized all Fapy pairs equally well and the activity was comparable to Tg. The results obtained in the nicking assay were further substantiated by the analysis of the Schiff base intermediate using NaBH(4) trapping assays. These results indicate that Escherichia coli and mammalian Tg glycosylases have a potential activity to recognize Fapy. However, as demonstrated for Fapy:C pairs, their distinctive activities implicate unequal participation in the repair of Fapy lesions in cells.