Effect of metformin on Wnt5a in individuals new-onset type 2 diabetes with different body mass indexes: The evidences from the real word research

Aim

Metformin is a first-line therapy for the treatment of Type 2 diabetes mellitus (T2DM), due to its inhibition of hepatic gluconeogenesis. Wingless family member 5a (Wnt5a) was significantly decreased in newly diagnosed T2DM patients and regulates secretion of β cells through the Wnt/calcium signalling cascades. This study aims to investigate how metformin works on glucose-lowering effects in diabetes and whether the mechanism underlying it is associated with Wnt5a.

Methods

A total of 144 participants were enrolled in this study. Serum Wnt5a levels were measured by an enzyme-linked immunosorbent assay (ELISA). The demographic and clinical parameters were evaluated in normal weight, overweight and obese new-onset T2DM subjects grouped.

Results

Wnt5a was increased in overweight T2DM patients and obese T2DM patients compared with the levels in normal Body Mass Index (BMI) T2DM. The level of Wnt5a gradually increased after 3 and 6 months of metformin treatment. Among the three groups, the most significant improvement in blood glucose was observed in the obese type 2 diabetic patients, and the improvement showed a significant correlation with Wnt5a protein after patients received metformin treatment. Pearson correlation showed that there was a significant relationship between △2hOGTT and Wnt5a. After further adjusting for sex and age, a significant association existed only between Wnt5a and 2-h oral glucose tolerance test(2hOGTT), and this association was negative.

Conclusion

Our results indicate that Wnt5a may play a role in the mechanism by which metformin improves blood glucose in patients with type 2 diabetes.

Effect of glucagon-like peptide-1 receptor agonist on insulin secretion index and serum Wnt5a protein in patients with new-onset type 2 diabetes mellitus

Objective

Previous studies have found that wnt5a promotes β-cell insulin secretion and reduced concentrations in patients with type 2 diabetes. GLP-1RA (Glucagon-like peptide-1 receptor agonists) can regulate insulin secretion. However, the evidence that GLP-1RA affect insulin secretion through the Wnt5a is inconclusive. Therefore, this study aimed to evaluate the effect of GLP-1 RA on wnt5a levels in patients with type 2 diabetes.

Methods

A total of 56 onset diabetics were selected our study, 29 of them were treated by GLP-1RAs (1.2mg subcutaneous injection once a day, liraglutide, Novo Nordisk), the rest (27 case) treated by Metformin (0.5 g twice a day, Glucophage, Merck). Individuals who were using medications to manage platelet (Aspirin) and cholesterol (Statins) were enrolled and continued treatment throughout the study.

Results

Our study found that the waist circumference and insulin secretion index in the GLP-1RA intervention group were significantly increased, and the insulin resistance index was lower than that of the control group. More interestingly, the serum Wnt5a protein level increased dramatically after the GLP-1RA intervention, and the level of Secreted frizzled-related protein 5 (Sfrp5) decreased compared with the control group. Multivariate linear regression analysis showed that the change of HOMA-β (Homeostasis model assessment- β) was significantly correlated with the changes of Wnt5a and Sfrp5, and the change of Wnt5a protein was positively correlated with HOMA-β.

Conclusion

Our results confirmed that GLP-1RA may improve HOMA-β in patients with type 2 diabetes by affecting the level of Wnt5a protein.

A Co-Designed Neuromorphic Chip With Compact (17.9K F2) and Weak Neuron Number-Dependent Neuron/Synapse Modules

Many efforts have been made to improve the neuron integration efficiency on neuromorphic chips, such as using emerging memory devices and shrinking CMOS technology nodes. However, in the fully connected (FC) neuromorphic core, increasing the number of neurons will lead to a square increase in synapse & dendrite costs and a high-slope linear increase in soma costs, resulting in an explosive growth of core hardware costs. We propose a co-designed neuromorphic core (SRCcore) based on the quantized spiking neural network (SNN) technology and compact chip design methodology. The cost of the neuron/synapse module in SRCcore weakly depends on the neuron number, which effectively relieves the growth pressure of the core area caused by increasing the neuron number. In the proposed BICS chip based on SRCcore, although the neuron/synapse module implements 1∼16 times of neurons and 1∼66 times of synapses, it only costs an area of 1.79 × 10⁷ F², which is 7.9%∼38.6% of that in previous works. Based on the weight quantization strategy matched with SRCcore, quantized SNNs achieve 0.05%∼2.19% higher accuracy than previous works, thus supporting the design and application of SRCcore. Finally, a cross-modeling application is demonstrated based on the chip. We hope this work will accelerate the development of cortical-scale neuromorphic systems.

[Association between high-density lipoprotein cholesterol level and cardiovascular disease and all-cause mortality in the elderly population]

Objective: To investigate the relationship between high density lipoprotein cholesterol (HDL-C) and cardiovascular disease (CVD) and all-cause mortality in the elderly population. Methods: A total of 14 355 elderly persons aged ≥65 years, who participated in the annual physical examination in Kailuan Group in 2006 were included in this prospective cohort study. According to HDL-C level, the participants were divided into 4 groups: low-level group (HDL-C<1.30 mmol/L), intermediate-level group (1.30 mmol/L ≤HDL-C≤1.54 mmol/L), medium-high-level group (1.55 mmol/L ≤HDL-C≤1.80 mmol/L), high-level group (HDL-C≥1.81 mmol/L). Baseline data such as age, sex and blood lipid levels were collected and compared. Inpatient medical records and death information were obtained through the social security system, and CVD and all-cause mortality were analyzed. After adjusting for confounding factors, the medium-high-level group was used as the reference group. Cox proportional risk regression model was used to evaluate the impact of HDL-C on CVD and all-cause mortality events. The linear or nonlinear relationship between HDL-C level and CVD and all-cause mortality events was evaluated by restricted cubic spline regression model. Death competitive risk analysis was conducted, and sensitivity analysis was performed after excluding subjects with CVD or all-cause mortality within 1 year of follow-up and female participants. Results: The average age of this cohort was (71.5±5.5) years and follow-up time was (10.9±3.3) years. Compared with medium-high-level group, Cox proportional risk regression analysis showed that the HR (95%CI) of CVD and all-cause mortality in low-level group were 1.21 (1.06-1.38) (P<0.05) and 1.02 (0.95-1.11) (P>0.05), respectively; the HR (95%CI) of CVD events in high-level group was 1.17 (1.03-1.33) (P<0.05), and there was a marginal significant association with all-cause mortality, the HR (95%CI) was 1.07 (1.00-1.16) (0.05<P<0.1). The restricted cubic spline regression analysis showed that HDL-C was nonlinearly correlated with CVD (nonlinear correlation P<0.1), and presented a U-shaped curve trend, while HDL-C was linearly correlated with all-cause mortality (nonlinear correlation P>0.1). Conclusions: In the elderly population, the risk of CVD is lowest when the HDL-C level is 1.55-1.80 mmol/L, either high or low HDL-C is a risk factor for CVD. High HDL-C tends to be related to increased risk of all-cause mortality and low HDL-C is not related to increased risk of all-cause mortality.

[Morvan syndrome with positive anti LGI1/CASPR2 antibodies in serum/cerebrospinal fluid:a case report and literature review]

To report a typical case of Morvan syndrome with positive anti-leucine rich glioma-inactivated 1(LGI1) and contactin-associated protein 2 (CASPR2) antibodies in serum and cerebrospinal fluid. A 39-years-old female initially presented weakness of extremeties. The main symptoms included paroxysmal limb pain, wheezing, itching, muscle twitching, epilepsy, hypomnesia, dysphoria, apathy, intractable insomnia, salivation and sweating. Tests of electrolytes found hypokalemia (2.7-3.1 mmol/L) and hyponatremia (130-136 mmol/L). Arterial blood gas analysis showed hypoxemia (oxygen saturation 50%-70%). Total thyroxine (TT4) was elevated to 207 nmol/L with positive thyroid peroxidase antibody (TPO-Ab) and thyroglobulin antibody (TG-Ab). LGI1and CASPR2 antibodies (CBA method) were positive in both serum and cerebrospinal fluid, and the remaining antibodies related to autoimmune encephalitis and paraneoplastic syndrome were negative. Head MRI was almost normal, while mild abnormalities were found in electroencephalogram. Electromyography showed slightly increased voltage of left quadriceps motor unit potential. After treated with corticosteroids, IVIG and mycophenolate mofetil, the patient completely improved. Cognitive function scores recovered from MoCA/MMSE (16/24) to MoCA/MMSE (26/29). Positivity of LGI1/CASPR2 antibodies both in serum/cerebrospinal fluid are rarely seen in patients with Morvan syndrome. Steroids and immunosuppressants are suggested for treatment as early as possible.

[C-reactive protein is associated with impaired working capacity in Chinese patients with ankylosing spondylitis in paid employment: the real-world evidence from Smart-phone SpondyloArthritis Management System]

To investigate the relationship between serum C-reactive protein (CRP) levels and work impairment in patients with ankylosing spondylitis (AS) based on real-world evidence. Outpatients with confirmed AS at Chinese PLA General Hospital were recruited consecutively by Smart-phone SpondyloArthritis Management System (SpAMS) from April 2016 to April 2018. The relationship between CRP and work productivity and activity impairment questionnaire (WPAI) were evaluated. Five hundred and fifty-one outpatients with AS in paid employment were recruited. The presenteeism, overall work impairment, and activity impairment rates increased by 1.4% (1.1%, 1.8%), 1.1% (0.5%, 1.6%), and 1.7% (1.3%, 2.1%), respectively, for every 10 mg/L increase in the CRP level (all P value<0.01). However, the CRP level was not associated with absenteeism after adjusting for covariates [0.5%(-0.4%, 1.0%),P>0.05]. There is a significant association between increased serum CRP levels at baseline and the previous 7-day work impairment in patients with AS. Higher CRP levels contribute to worse presenteeism, overall work impairment, and activity impairment rates, which suggests the necessity of monitoring CRP on treatment, and also indicates that anti-inflammatory therapy may be effective for improving work productivity.

[Necessity of repeated renal arteriography in the treatment of severe hemorrhage after percutaneous nephrolithotomy]

In order to discuss the necessity of repeated renal arteriography in the treatment of severe bleeding after percutaneous nephrolithotomy, this study retrospectively analyzed the clinical data of patients with severe bleeding after percutaneous nephrolithotomy in the Department of Urology Surgery of the First Hospital of China Medical University from August 2010 to July 2020, summarily analyzing treatments, outcomes and follow-up results of 27 patients who were treated by renal arteriography more than twice. Of these 27 patients who underwent repeated renal arteriography, 23 of them were treated by two times, 4 by three times, all of whom were diagnosed as renal vascular injury. And 15 of them were diagnosed as pseudoaneurysm, 4 of them renal arteriovenous fistula, and 8 of them pseudoaneurysm combined with renal arteriovenous fistula. After clear diagnosis, all these patients were performed with renal artery embolization, after which the symptoms of hematuria and lumbar discomfort were relieved or disappeared immediately. These patients were followed up from 6 months to 5 years, without corresponding symptoms recurring and with the renal function equivalent to that before embolization. The results showed that repeated renal arteriography was of great significance in the treatment of patients with severe bleeding after percutaneous nephrolithotomy, helping to clarify the cause of bleeding and giving appropriate and timely treatment.

Pancreatic Fat is not significantly correlated with β-cell Dysfunction in Patients with new-onset Type 2 Diabetes Mellitus using quantitative Computed Tomography

Objective: Type 2 diabetes mellitus (T2DM) is a chronic condition resulting from insulin resistance and insufficient β-cell secretion, leading to improper glycaemic regulation. Previous studies have found that excessive fat deposits in organs such as the liver and muscle can cause insulin resistance through lipotoxicity that affects β-cell function. The relationships between fat deposits in pancreatic tissue, the function of β-cells, the method of visceral fat evaluation and T2DM have been sought by researchers. This study aims to elucidate the role of pancreatic fat deposits in the development of T2DM using quantitative computed tomography (QCT), especially their effects on islet β-cell function. Methods: We examined 106 subjects at the onset of T2DM who had undergone abdominal QCT. Estimated pancreatic fat and liver fat were quantified using QCT and calculated. We analysed the correlations with Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) scores and other oral glucose tolerance test-derived parameters that reflect islet function. Furthermore, correlations of estimated pancreatic fat and liver fat with the area under the curve for insulin (AUC_INS) and HOMA-IR were assessed with partial correlation analysis and demonstrated by scatter plots. Results: Associations were found between estimated liver fat and HOMA-IR, AUC_INS, the modified β-cell function index (MBCI) and Homeostatic Model Assessment β (HOMA-β). However, no significant differences existed between estimated pancreas fat and those parameters. Similarly, after adjustment for sex, age and body mass index, only estimated liver fat was correlated with HOMA-IR and AUC_INS. Conclusions: This study suggests no significant correlation between pancreatic fat deposition and β-cell dysfunction in the early stages of T2DM using QCT as a screening tool. The deposits of fat in the pancreas and the resulting lipotoxicity may play an important role in the late stage of islet cell function dysfunction as the course of T2DM progresses.

Wingless-Type MMTV Integration Site Family Member 5a Is a Key Secreted Islet Stellate Cell-Derived Product that Regulates Islet Function

BACKGROUND

Emerging evidence suggests that T2DM is attributable to the dysfunction of β-cells and the activation of islet stellate cells (ISCs). The wingless-type MMTV integration site family member 5a (Wnt5a)/frizzled 5 (Fzd5) signalling pathway might take part in this process. Our study is aimed at defining the status of ISCs during β-cell insulin secretion homeostasis by determining the role of the Wnt5a protein in the regulation of insulin production. We examined the effects of the status of ISCs on β-cell insulin secretion in normoglycemic db/m and hyperglycaemic db/db mice.

METHODS

iTRAQ protein screening and RNA interference were used to determine novel ISC-derived secretory products that may use other mechanisms to influence the function of islets.

RESULTS

We showed a significant reduction in insulin secretion by β-cells in vitro when they were cocultured with db/db ISCs compared to when they were cocultured with ISCs isolated from normoglycemic db/m mice; in addition, both Wnt5a and its receptor Fzd5 were more highly expressed by quiescent ISCs than by activated db/db ISCs. Treatment with exogenous Wnt5a increased the secretion of insulin in association with the deactivation of ISCs.

CONCLUSION

Our observations revealed that the Wnt5a protein is a key effector of ISC-mediated improvement in islet function.

Corrigendum to "Wingless-Type MMTV Integration Site Family Member 5a Is a Key Secreted Islet Stellate Cell-Derived Product that Regulates Islet Function"

[This corrects the article DOI: 10.1155/2019/7870109.].

Biodegradable poly-lactic acid based-composite reinforced unidirectionally with high-strength magnesium alloy wires

Biodegradable poly-lactic acid (PLA)--based composites reinforced unidirectionally with high-strength magnesium alloy wires (MAWs) are fabricated by a heat-compressing process and the mechanical properties and degradation behavior are studied experimentally and theoretically. The composites possess improved strengthening and toughening properties. The bending strength and impact strength of the composites with 40 vol% MAWs are 190 MPa and 150 kJ/m(2), respectively, although PLA has a low viscosity and an average molecular weight of 60,000 g/mol. The mechanical properties of the composites can be further improved by internal structure modification and interface strengthening and a numerical model incorporating the equivalent section method (ESM) is proposed for the bending strength. Micro arc oxidization (MAO) of the MAWs is an effective interfacial strengthening method. The composites exhibit high strength retention during degradation and the PLA in the composite shows a smaller degradation rate than pure PLA. The novel biodegradable composites have large potential in bone fracture fixation under load-bearing conditions.

First-principles investigation of the structural and elastic properties of Be12Ti under high pressure

The effects of pressure on the structural and elastic properties of Be₁₂Ti were investigated by the generalized gradient approximation (GGA) with a Perdew–Burke–Ernzerhof (PBE) exchange-correlation function using density-functional theory.

TGF-beta induced RBL2 expression in renal cancer cells by down-regulating miR-93

PURPOSE

TGF-beta can induce G1 arrest via many mechanisms including up-regulating p21, p27, and Rb. However, as the member of Rb family, whether RBL2 is induced by TGF-beta treatment remains exclusive.

METHODS

The expression of RBL2 and miR-93 after TGF-beta treatment was determined by quantitative real-time PCR and western blot. The growth of renal cancer cells was determined by CCK-8 assays and cell cycle was determined by PI staining. The binding of miR-93 on RBL2 3'-UTR was determined by double luciferase system.

RESULTS

In renal cancer cells, TGF-beta treatment induced expression of RBL2 in a time- and concentration-dependent manner, and RBL2 mediated TGF-beta induced growth inhibition and cell cycle arrest in renal cancer cells. Furthermore, we found that miR-93 directly targeted RBL2 by binding to its 3'-UTR in renal cancer cells. Over-expression of miR-93 significantly reduced the expression of RBL2, whereas knock down of miR-93 up-regulated the expression of RBL2. More importantly, TGF-beta treatment inhibited miR-93 expression, which resulted in up-regulation of RBL2 after TGF-beta treatment.

CONCLUSION

TGF-beta induced RBL2 expression through down-regulating miR-93 in renal cancer cells. The newly identified TGF-beta/miR-93/RBL2 signal pathway reveals a new mechanism of TGF-beta induced growth arrest in renal cancer.

Bandwidth improvement for slow light using amplification characteristics of cascaded vertical-cavity surface-emitting lasers

A scheme to improve the bandwidth of slow light using cascaded vertical-cavity surface-emitting lasers (VCSELs) is proposed and experimentally demonstrated. In the scheme, a proper adjustment on the gain peaks of two cascaded VCSELs enables the generation of the desired composite gain spectrum, which has flat-top gain and delay profiles with enhanced peak values. By employing the improved gain and delay profiles in a slow light system, a large delay can be achieved within a wider bandwidth. In the experiment, by using two cascaded VCSELs, a tunable slow light up to 135 ps for a 5 Gbits/s pseudorandom binary sequence is demonstrated with relatively low signal distortion.

Genetic diversity and variation of saponin contents in Panax notoginseng roots from a single farm

Radix notoginseng, the root of Panax notoginseng (Burk.) F. H. Chen, has been widely used in traditional Chinese medicine. Its main components, saponins, have been reported to have many pharmacological activities. To test the general assumption that herbs of a single species planted and harvested from a single location are uniform in chemical and genetic makeup, chemical analysis and DNA fingerprinting were carried out. High-performance TLC together with HPLC analysis were used to analyze 17 randomly sampled 3-year-old roots from a single farm for the presence of six saponins. Five roots showed distinct chemical profiles with changed ratios of ginsenosides Rd/Rg1, Re/Rg1, or Rb1/Rg1. The same samples, together with some 1- and 2-year-old samples, were also subjected to fluorescent amplified fragment length polymorphism (AFLP) analysis, and their internal transcribed spacer 2 (ITS 2) regions were sequenced. Fluorescent AFLP analysis was found to be much more polymorphic than the ITS 2 sequence and showed clear evidence of genetic diversity within the tested population. In conclusion, genetic diversity and variation of saponin contents between individual P. notoginseng roots have been detected. We suggest that genetic diversity affects the contents of the six saponins. The saponin contents variation and genetic diversity were also found among P. notoginseng root samples collected from China and Singapore markets. Since variable saponin contents may affect therapeutic efficacy, combining the use of genetic profiling with chemical profiling will help ensure greater uniformity in the quality of P. notoginseng roots. The genetic and chemical diversity within a population also provides the opportunity for breeding new cultivars with more desirable chemical constituents.

The biological behaviour of human adenoid cystic carcinoma cells transduced with interleukin-2-gene

Adenoid cystic carcinoma (ACC) of the salivary glands is a highly infiltrative malignant tumour with a tendency for lung metastasis. Gene therapy could be a potentially effective therapy for ACC and its metastasis. The aims of the study were: To transduce interleukin-2 (IL-2) gene into an ACC cell line with predisposition for lung metastasis (ACC-M); to compare the bioactivity of the gene-transduced cells and the parent cell line in vitro and in vivo. The IL-2 gene was transduced via a bicistronic retroviral vector into the ACC-M cells. The growth rate and DNA cell cycles of the parent ACC-M, the control viral vector AmGCEN, and the gene transduced AmIL-2 cell cultures were compared quantitatively and by flow cytometry, respectively. The tumourigenic ability of the three cell lines was verified by inoculation in athymic nude mice. The tumours developed were extracted and compared quantitatively and histologically. There was no difference in the growth rate and the DNA count between the ACC-M, AmGCEN, and AmIL-2 cell cultures. In the animal experiment, both the ACC-M and AmGCEN cells stimulated lung metastasis in all the mice, whereas there was no tumour found in the 1 x 10(6) AmIL-2 cells inoculation. On 3 x 10(6) AmIL-2 cells stimulation, three out of six mice developed tumours but the mass and volume of the tumours were smaller than the other two groups. Under light microscopy, the ACC-M tumours were mainly poorly differentiated with minimal cellular matrix, whereas the AmIL-2 tumours were well differentiated with ample matrix. The transduction of IL-2 gene can reduce the tumourigenicity of ACC-M cells and induces tumour cell differentiation in mice. The IL-2 gene can be a potential effective gene for the treatment of adenoid cystic carcinoma of salivary glands and its lung metastasis.

[A study of the magnification of mandible pantomography image]

OBJECTIVE

To study the degree of magnification of mandible pantomography image.

METHODS

The pantomography of 50 mandible specimens marked with lead pellets were taken by TROPHY XL-90C. The distances between each markers on film and in specimen were measured.

RESULTS

The mean magnification(MM) of mandible pantomography image with TROPHY XL-90C was 1.22. MM of horizontal axle was 1.14. MM of vertical axle was 1.29. MM of horizontal axle was greatest (1.24) in the body of mandible,and lest (1.08) in genion. MM of vertical axle is similar among each regions. MM of vertical axle was greater than that of horizontal axle in all regions.

CONCLUSION

The MM parameters of mandible pantomography image were useful to estimate the size of mandible lesions and provided a basis for dental implant more exactly.

Drug-induced QT prolongation in women during the menstrual cycle

CONTEXT

Women have a higher incidence of torsades de pointes than men, but it is not known if the risk of drug-induced torsades de pointes varies during the menstrual cycle.

OBJECTIVES

To determine if the degree of QT prolongation in response to ibutilide varies with the menstrual cycle phase and to compare QT prolongation between women and men.

DESIGN AND SETTING

Cohort study of men and women who received the same intervention conducted between November 1998 and November 2000 at a general clinical research center of a university hospital.

PARTICIPANTS

A volunteer sample of 58 healthy adults (38 men and 20 women) aged 21 to 40 years.

INTERVENTION

A low dose of ibutilide (0.003 mg/kg), infused intravenously for 10 minutes. Subjects were monitored for 120 minutes. Women received the intervention on 3 separate occasions to correspond with menstrual cycle phases, which were verified by using hormonal assays.

MAIN OUTCOME MEASURE

QT interval, recorded from electrocardiogram at timed intervals during and after ibutilide infusion and standardized for variations in heart rate (QTc).

RESULTS

Maximum (mean [SD]) millisecond increase in QTc after ibutilide infusion was greater for women during menses (63 [13]) and the ovulatory phase (59 [17]) compared with women during the luteal phase (53 [14]) and compared with men (46 [16]; P =.002 vs menses and P =.007 vs ovulation). Progesterone (r = -0.40) and progesterone-to-estradiol ratio (r = -0.41), but not estradiol (r = 0.14) or testosterone (r = 0.09), were inversely correlated with ibutilide-induced QT prolongation.

CONCLUSIONS

Menstrual cycle and sex differences exist in QTc responses to ibutilide, with the greatest increase in QTc corresponding to the first half of the menstrual cycle.

[Ultramicrostructural observation on epithelial cell disdifferentiation in rat tongue carcinogenesis induced by 4NQO]

OBJECTIVE

To clarify epithelial cell ultramicrostructure changes in oral carcinogenesis.

METHODS

The epithelial cell ultramicrostructures in tongue carcinogenesis induced by 4-nitroquinoline-1-oxide (4NQO) were observed by transmission electron microscope.

RESULTS

With the progress of oral carcinogenesis, regular changes of epithelial cell were showed: decrease in tonofibril, keratohyaline granules, desmosome; and increase in mitochondria. The basement membrane was broken in some severe dysplasia (sDP) and was broken through by parts of cell processes in in situ carcinoma (ISC).

CONCLUSION

Oral carcinogenesis is a multistep process. Epithelial cell aberrant differentiation is showed by a decrease in the synthetic products of epithelium cell.

[Epidemiology of dental caries and periodontal diseases in middle school students in Suzhou City]

OBJECTIVE

To assess the prevalence of dental caries and periodontal diseases in middle school students at the ages of 11 to 13 and 15 to 17.

METHODS

Dental caries and periodontal diseases were assessed strictly by "national survey table of dental caries and periodontal diseases for school students".

RESULTS

The study group consisted of 20 581 students. The percentage of dental caries, DMFT and DMFS in students 11 to 13 years of age were 23.6%,0.40 and 0.54, respectively. The corresponding results were 29.76%, 0.64 and 0.87 for students 15 to 17 years of age, respectively. The percentage of gingivitis and dental calculus in students 11 to 13 years were 75.33% and 35.86%, respectively. The corresponding values in students 15 to 17 years of age were 73.1% and 44.91%, respectively. Female students have significantly few gingivitis and dental calculus than male students in both groups.

CONCLUSION

Compared with the students at the same ages in other cities, students in Suzhou city have low percentage of dental caries and periodontal diseases.

[Experimental study of abnormal cell proliferation and differentiation in rat tongue carcinogenesis induced by 4NQO]

OBJECTIVE

To clarify the phenotypic characteristics of abnormal cell proliferation and differentiation in oral carcinogenesis.

METHODS

The expressions of gp230, a marker of epithelium cell differentiation, and proliferating cell nuclear antigen (PCNA) in rat tongue carcinogenesis induced by 4-nitroquinoline-1-oxide (4NQO) were detected by LSAB immunohistochemical staining.

RESULTS

With the progress of oral carcinogenesis abnormal proliferation and differentiation patterns were indicated by reduced expression of gp230 and increased expression of PCNA.

CONCLUSION

Oral carcinogenesis is the result of mucosa epithelium cell aberrant proliferation and differentiation.

Effects of all-trans retinoic acid and interferon-gamma on expression of RAR beta gene in Tca8113 cells

OBJECTIVE

All-trans-retinoic acid (ATRA) and interferons (IFNs) have been proven to synergistically amplify growth inhibition and apoptosis in the tongue squamous carcinoma cell line (Tca8113). Nuclear retinoic acid receptor-beta (RAR beta) was the key gene that mediated retinoid activity for squamous carcinoma cells. In order to understand the mechanism of ATRA combined with IFN gamma inhibiting growth of Tca8113 cells, this investigation focused on RAR beta mRNA expression.

MATERIALS AND METHODS

In this experiment, RT-PCR method was used to analyze the RAR beta expression level, and viable cell count assay was carried out for growth inhibition studies.

RESULTS

All-trans-retinoic acid (1 microM) and IFN gamma (1000 u/mL) inhibited cell growth by 39.2% and 44.4%, respectively. Synergistic inhibition of cell proliferation by 86.7% was found under combined treatment. The combination of suboptimal concentrations of ATRA (0.1 microM) with IFN gamma (1000 u/mL) showed a much stronger additive inhibitory effect on cell proliferation. ATRA (1 microM) and IFN gamma (1000 u/mL) increased RAR beta expression to 4 times and 3 times, respectively. The expression of RAR beta increased 12 times after treatment with combined ATRA and IFN gamma treatment.

CONCLUSIONS

These observations indicated that the use of combined ATRA and IFN may lead to enhanced antitumor effects. These results also suggested that ATRA and IFN mediated upregulating expression of RAR beta may play an important role in synergistic inhibition of proliferation in Tca8113 cells.

Female gender is a risk factor for torsades de pointes in an in vitro animal model

Recent clinical observations indicate that female gender is associated with a higher risk of developing torsades de pointes (TdP) cardiac arrhythmia. In this study, we used the Langendorff technique in isolated perfused rabbit hearts and the whole-cell patch-clamp technique in ventricular myocytes to examine the gender difference in TdP incidence and gain insight into the underlying mechanisms. Isolated rabbit hearts were perfused by using the Langendorff technique. TdP was induced by abrupt changes of cycle length (deltaCL) in the presence of Tyrode's solution containing 1 mM 4-aminopyridine (4AP) and 50% reduced Mg2+ and K+ (low K/Mg). The effects of 1 mM 4AP on cardiac potassium currents were characterized by using the patch-clamp technique. Results demonstrated that (a) no significant gender difference was observed in the absolute QT interval before or after 4AP perfusion in the presence of low K/Mg; (b) 4AP caused marked QT prolongation in the ECG; (c) a significantly higher TdP incidence (nine of 12) was found in female hearts compared with male hearts (three of 12; p < 0.05); (d) 1 mM 4AP primarily inhibited Ito, although a slight inhibition of IKr also occurred in low-K/Mg Tyrode's solution. (e) No inhibition of IK1 was observed. (f) No gender difference was found in the potassium current block produced by 4AP. Female gender is associated with a higher incidence of TdP in an experimental isolated heart model and mechanisms subsequent to QT prolongation may contribute to such a gender difference.

Comparison of tegaserod (HTF 919) and its main human metabolite with cisapride and erythromycin on cardiac repolarization in the isolated rabbit heart

Tegaserod (HTF 919) is a new drug being developed for gastrointestinal motility disorders. Because other gastrointestinal prokinetic agents, such as cisapride and erythromycin, cause slowing of cardiac repolarization and have been implicated in the development of the potentially fatal ventricular arrhythmia, torsades de pointes, a study was initiated to determine whether tegaserod and its main human metabolite adversely influence cardiac repolarization. By using isolated Langendorff-perfused rabbit hearts, we show that QT intervals remain unchanged at concentrations of tegaserod from 0.5 to 10 microM. It was not until the tegaserod concentration was increased to 50 microM (roughly 500-5,000 times more concentrated than those typically found in human plasma after administration of recommended clinical dosages), that a small, but significant increase in the QT interval (12+/-4%; p < 0.05; n = 4) was observed. No significant changes in QT occurred in the presence of the tegaserod metabolite at any of the concentrations tested (0.5-50 microM). In contrast, cisapride caused QT lengthening at concentrations as low as 0.1 microM, with significant QT increases occurring when 5-50 microM cisapride was used (22+/-4% to >70%, respectively; p < 0.01; n = 4). Erythromycin also caused significant lengthening of QT intervals (11+/-2%; p < 0.001; n = 4), although 100 microM concentrations of this drug were required to achieve this effect. These results demonstrate that both cisapride and erythromycin can slow cardiac repolarization at therapeutic doses and that tegaserod's lack of QT prolongation at therapeutic doses suggests that it has the potential to be a safer alternative to cisapride as a gastrointestinal prokinetic agent.

Prolongation of QT interval in isolated feline hearts by antipsychotic drugs

Some antipsychotic drugs have been found to prolong the QT interval on electrocardiographic (ECG) recordings, a phenomenon which, when severe, may facilitate the occurrence of complex ventricular arrhythmias such as torsade de pointes. However, the effects of these drugs on the cardiac repolarization process have not been evaluated extensively. This study was designed to examine the potency of five antipsychotic drugs in lengthening the QT interval of the perfused feline heart: haloperidol, risperidone, sertindole, clozapine, and olanzapine. The hearts were infused with increasing concentrations of drugs (0.1-20 micromol/L) for 40-minute intervals at each concentration. ECG recordings were made, with signals amplified and data recorded on a strip chart recorder. Four representative beats from each set of three signal recordings were chosen for QT interval measurement. Our data indicated that all tested drugs prolonged the QT interval in a concentration-dependent manner (p < 0.01). Haloperidol and risperidone were significantly more potent than sertindole, clozapine, and olanzapine (p < 0.001). At a concentration of 0.5 micromol/L over a 40-minute infusion interval, haloperidol lengthened the interval by 26.2+/-0.7%, risperidone by 19.4+/-2.2%, and sertindole by 8.9+/-3.5% (p < 0.05 compared with baseline); clozapine and olanzapine were less potent. Although species differences may limit extrapolation of our findings to humans, the cardiac potassium channels of felines clearly resemble those of humans. This model may serve as the basis for further studies of drug-induced prolongation of the QT interval and precipitation of ventricular arrhythmias.

The antiestrogen tamoxifen blocks the delayed rectifier potassium current, IKr, in rabbit ventricular myocytes

Tamoxifen is an antiestrogen drug commonly used to treat breast cancer and has been shown to cause prolongation of the electrocardiographic QT interval in humans. Because QT prolongation could influence cardiac arrhythmias, we sought to determine the electrophysiologic mechanism(s) underlying the tamoxifen action. The whole-cell patch-clamp technique was used to study the effect of tamoxifen on the delayed rectifier (IKr), the inward rectifier (IK1), the transient outward current (Ito), and the inward L-type calcium current (ICa) in rabbit ventricular myocytes. By switching to the current-clamp mode, the effect of tamoxifen on action potential duration (APD) was also studied. Tamoxifen blocked IKr in a time-, concentration- and voltage-dependent fashion. IKr tail currents were completely blocked by 10 micromol/l tamoxifen with no recovery after 15 min of washout. At +50 mV, tamoxifen 1 and 3.3 micromol/l blocked IKr by 39.5 +/- 1.7% (P <.01) and 84.8 +/- 1.3% (P <.01) respectively, while no significant block of IK1 or Ito was observed. Significant block of ICa by tamoxifen was also observed at concentrations greater than 1 micromol/l, with almost complete inhibition at 10 micromol/l. Tamoxifen showed no significant effect on APD at concentrations up to 3.3 micromol/l. We conclude that tamoxifen potently blocks both IKr and ICa at clinically relevant concentrations. The observed QT prolongation by tamoxifen in humans may be a result of its predominant effect on IKr. Inhibition of IKr, in conjunction with other QT-prolonging factors in patients could increase their risk of developing torsades de pointes-type cardiac arrhythmias.

"Conventional" antihistamines slow cardiac repolarization in isolated perfused (Langendorff) feline hearts

We examined the effects of "conventional" antihistamines on cardiac repolarization by using the isolated perfused feline heart model. Representative drugs from the major classes of antihistamines were tested. Each of the antihistamines evaluated in this study elicited a dose-dependent slowing of cardiac repolarization, as indicated by the QT prolongations observed from electrocardiogram (ECG) tracings recorded during these experiments. The concentrations of drugs tested ranged from 1 to 30 microM. Of the drugs analyzed, clemastine and hydroxyzine appeared to be the most potent (relative EC50 values, 5.2 and 6.6 microM, respectively), causing the QT to lengthen by as much as 40-50% at a concentration of 10 microM. Brompheniramine, chlorpheniramine, and diphenhydramine displayed intermediate potencies with respect to QT prolongation (relative EC50 values, 11-13 microM), whereas cyproheptadine, chlorcyclizine, and promethazine were the least potent of the antihistamines tested (relative EC50 values, 16-20 microM). It is concluded that the antihistamines evaluated in this study act directly on the heart to slow cardiac repolarization. These findings could have important clinical relevance for patients taking excessive dosages of conventional antihistamines and those at risk of developing cardiac arrhythmias.

Female gender as a risk factor for drug-induced cardiac arrhythmias: evaluation of clinical and experimental evidence

One of the most pronounced gender-based differences in response to drugs is women's far greater risk of developing the life-threatening ventricular arrhythmia called torsades de pointes (TdP). A review of the literature and databases of the Food and Drug Administration reveals that a much higher percentage of women than men develop TdP arrhythmias after taking a variety of drugs, such as antihistamines (terfenadine, astemizole), antibiotics (erythromycin), antimalarials (halofantrine), antiarrhythmics (quinidine, d-sotalol), and miscellaneous other drugs. All of these drugs have in common the ability to block potassium currents, thereby prolonging cardiac repolarization and the QT interval on the ECG. The available experimental data support the hypothesis that gender differences in specific cardiac ion current densities are responsible, at least in part, for the greater susceptibility of females for developing TdP arrhythmias. In isolated perfused rabbit hearts (Langendorff technique), female rabbit hearts display greater baseline and drug-induced (quinidine and d-sotalol) changes in QT intervals than male hearts, and at least two different repolarizing potassium current densities (IKr and IKl) are found to be significantly lower in ventricular cardiomyocytes from female rabbits compared with those from males. Thus, it appears that as in humans, clear gender differences exist in the electrophysiologic characteristics governing cardiac repolarization in rabbits. This model and perhaps others should be examined as predictors of functional and pharmacologic differences between men and women. Understanding the potential mechanisms responsible for the greater risk of drug-induced arrhythmias in women could lead to screening methods for identification of individuals at risk for drug-induced arrhythmias or to the development of drugs with reduced risk of inducing arrhythmia.

Gender difference in the cycle length-dependent QT and potassium currents in rabbits

Women are known to have a longer electrocardiographic Q-T than men, which may contribute to their being at greater risk of developing drug-induced polymorphic ventricular arrhythmias. However, little is known about the underlying mechanisms. In the present study, we evaluated potential gender differences in Q-T interval in isolated perfused rabbit hearts using the Langendorff technique and evaluated the density of outward potassium currents in single ventricular myocytes using the whole-cell patch-clamp technique. We found that female hearts demonstrated a greater Q-T lengthening (delta Q-T%) upon an increase in cycle length (CL), resulting in a significantly longer Q-T (301 +/- 4.8 ms, CL = 2.3 s) at a long CL in female hearts compared with male hearts (267 +/- 4.0 ms, P < .01). Ventricular myocytes isolated from female hearts showed a smaller IK(tail) and peak IKI outward current density. A 50% reduction in extracellular K+ and Mg++ shifted the I-V relationship of IKI and Ito and reduced their amplitude. However, neither the I-V relationship of IKr nor the gender difference in the Q-T-CL relationship was significantly altered. We conclude that 1) female rabbit ventricular myocytes have significantly lower IKr and IKl outward current densities than do male cells, which may contribute to the gender difference in Q-T, and 2) a lower base-line IKr density may contribute to the steeper Q-T-CL relationship in female hearts.

Nitric oxide inhibits Oct-1 DNA binding activity in cultured vascular smooth muscle cells

Since Oct-1 is a ubiquitous DNA binding protein shown to play an important role in regulating cell proliferation and possess structural characteristics consistent with a nitric oxide (NO) target, we studied NO regulation of the DNA binding activity of Oct-1 in the A7R5 vascular smooth muscle cell (VSMC) line. Two NO donors, sodium nitroprusside (SNP) and S-nitroso-N-acetyl-penicillamine (SNAP) were directly added to the nuclear extract-oligonucleotide reaction mixture, respectively and the effect on Oct-1 DNA binding activity was evaluated by gel shift assay. Both NO donors (0.01-1 mM) inhibited the DNA binding activity of Oct-1. This inhibitory effect was not attenuated by dithiothreitol (DTT) (1 mM) while in contrast, DTT did antagonize the effect of diamide on Oct-1 DNA binding activity. The NO effect on Oct-1 has some specificity; as the NO donors had no effect on myc DNA binding activity. The inhibitory effect of NO donors was reproduced in A7R5 cells, without affecting their viability. These findings provide the first evidence that NO inhibits the DNA binding activity of Oct-1, probably through a cGMP independent mechanism and suggests that NO may inhibit mitogenesis in part through an effect on Oct-1 DNA binding activity in VSMCs.

Pyridyloxobutyl adduct O6-[4-oxo-4-(3-pyridyl)butyl]guanine is present in 4-(acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone-treated DNA and is a substrate for O6-alkylguanine-DNA alkyltransferase

The lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is activated to reactive metabolites that methylate or pyridyloxobutylate DNA. Previous studies demonstrated that pyridyloxobutylated DNA interferes with the repair of O6-methylguanine (O6-mG) by O6-alkylguanine-DNA alkyltransferase (AGT). The AGT reactivity of pyridyloxobutylated DNA was attributed to (pyridyloxobutyl)guanine adducts. One potential AGT substrate adduct, 2'-deoxy-O6-[4-oxo-4-(3-pyridyl)butyl]guanosine (O6-pobdG), was prepared. This adduct was stable at pH 7.0 for greater than 13 days and to neutral thermal hydrolysis conditions (pH 7.0, 100 degrees C, 30 min). Under mild acid hydrolysis conditions (0.1 N HCl, 80 degrees C), O6-pobdG was depurinated to yield O6-[4-oxo-4-(3-pyridyl)butyl]guanine (O6-pobG). O6-pobdG was hydrolyzed to 4-hydroxy-1-(3-pyridyl)-1-butanone and guanine under strong acid hydrolysis conditions (0.8 N HCl, 80 degrees C). O6-pobG was detected in 0.1 N HCl hydrolysates of DNA alkylated with the model pyridyloxobutylating agent 4-(acetoxymethylnitrosamino)-1-(3-[5-3H]pyridyl)-1-butanone ([5-3H]NNKOAc). When [5-3H]NNKOAc-treated DNA was incubated with either rat liver or recombinant human AGT, O6-pobG was removed, presumably a result of transfer of the pyridyloxobutyl group from the O6-position of guanine to AGT's active site.

Pyridyloxobutylation of guanine residues by 4-[(acetoxymethyl)nitrosamino]-1-(3-pyridyl)-1-butanone generates substrates of O6-alkylguanine-DNA alkyltransferase

Pyridyloxobutylation of DNA yields adducts that react with O6-alkylguanine-DNA alkyl-transferase (AGT) to prevent the repair of O6-methylguanine (O6-mG). The chemical characterization of pyridyloxobutyl adducts has been confounded by their instability under DNA hydrolysis conditions. They decompose to 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB) during the chemical or enzymatic hydrolysis of DNA. The goal of these studies was to determine which bases are pyridyloxobutylated to form AGT-reactive adducts. The model pyridyloxobutylating agent, 4-[(acetoxymethyl)nitrosamino]-1-(3-pyridyl)-1-butanone (NNKOAc), was reacted with either poly(dAdT) or poly(dGdC) to generate DNA substrates for reaction with AGT. Only the pyridyloxobutylated poly(dGdC) was able to prevent the ability of partially purified rat liver AGT to repair O6-mG. These results paralleled those obtained for the corresponding methylated substrates. These studies are consistent with the pyridyloxobutylation of GC base pairs and not AT base pairs in the DNA to generate a substrate for AGT. In order to distinguish between the formation of reactive adducts at C residues versus G residues, two oligomers were designed that were complementary to one another. One oligomer contained A, T, and G residues, whereas its complement contained T, A, and C residues. Only the dG-containing oligomer reacted with NNKOAc to generate an AGT-reactive adduct, again paralleling the results obtained for a methylating agent. These results demonstrate that pyridyloxobutylation of only guanine residues produces adducts that react with AGT. These AGT-reactive guanine adducts are relatively stable within DNA, with a half-life of 1-2 weeks at 37 degrees C. They represent up to 70% of the total HPB-releasing adducts in the NNKOAc-treated DNA. We postulate that a potential AGT-reactive adduct is an O6-(pyridyloxobutyl)guanine adduct.

Enhancement of cardiac function by cyclocreatine in models of cardiopulmonary bypass

This study tests the hypothesis that the administration of cyclocreatine prior to global ischemia enhances recovery of cardiac function during reperfusion. Two models were used. First, in a Langendorff-working heart model of normothermic cardioplegic arrest, rats (n = 6 per group) were injected intravenously with saline or cyclocreatine (600, 300, or 150 mg/kg). After 30 min or 2 h, hearts were excised and perfused in the Langendorff mode for 5 min and then in the working heart mode for 20 min. Normothermic arrest was induced by infusing warm St. Thomas solution once; then hearts were kept at 37 degrees C for 40 min. Following arrest, hearts were reperfused in the Langendorff mode for 15 min and then in the working mode for 30 min. Cyclocreatine consistently produced significantly better recovery of aortic flow and cardiac output compared to that of saline hearts. Second, in an intact canine model of cold cardioplegic arrest, adult mongrel dogs (n = 3 to 6 per group) underwent aortic cross-clamping for 1 h, followed by reperfusion on bypass for 45 min and off bypass for 4 h. Dogs were injected intravenously with saline or cyclocreatine (500 mg/kg) for 1 h before experiment. Post-bypass segmental contractility and cardiac output were significantly better in cyclocreatine hearts compared to that of controls. In a limited study, after a 3 h aortic cross-clamp time, cyclocreatine hearts achieved 91% baseline function while control hearts failed after 2 h. Results of this study suggest that cyclocreatine, without inotropic or chronotropic effect, protects the heart from global ischemic injury.

Pyridyloxobutyl DNA adducts inhibit the repair of O6-methylguanine

The carcinogenic tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), both methylates and pyridyloxobutylates DNA. O6-Methylguanine (O6-mG) persistence has been correlated to NNK-induced lung tumor formation in A/J mice. The pyridyloxobutylation pathway enhances the tumorigenicity of the methylation pathway. In this paper we test the hypothesis that DNA pyridyloxobutylation increases O6-mG persistence by inhibiting the repair protein O6-alkylguanine-DNA alkyltransferase (AGT). Pyridyloxobutylated DNA was generated by reacting calf thymus DNA with the model pyridyloxobutylating agent 4-(acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone (NNKOAc) in the presence of esterase. The alkylated DNA inhibited the ability of partially purified rat liver AGT to repair O6-mG when it was incubated with AGT prior to the addition of 3H-methylated DNA. The extent of inhibition was dependent on the amount of NNKOAc reacted with DNA. The ability of NNKOAc-treated DNA to inhibit AGT was destroyed when the DNA was subjected to neutral thermal hydrolysis. Approximately 1 pmol of AGT was inhibited for every 25 to 50 pmol of 4-hydroxy-1-(3-pyridyl)-1-butanone- releasing adducts present in NNKOAc-treated DNA. The inhibitory activity of this alkylated DNA was relatively stable under physiological conditions (pH 7.4, 37 degrees C). Only 13% of the AGT reactive activity was lost after 7 days. When pyridyloxobutylated DNA was incubated simultaneously with 3H-methylated DNA and AGT, a significant reduction in [3H]methyl transfer to AGT was observed. The levels of reduction were similar to those observed when unlabeled methylated DNA containing comparable levels of O6-mG was substituted for NNKOAc-treated DNA. Based on these results, a cocarcinogenic role for pyridyloxobutylation in NNK-induced lung tumorigenesis is proposed in which pyridyloxobutyl DNA adduct(s) compete with O6-mG for reaction with AGT resulting in sustained levels of O6-mG. These enhanced levels then increase the probability of tumor induction by NNK.

Salicylate reduces ventricular dysfunction and arrhythmias during reperfusion in isolated rat hearts

Recent studies have shown the ability of salicylic acid (SA) to trap hydroxyl radicals (OH.) generated during reperfusion in ischemic myocardium. Since OH. is implicated in the pathogenesis of reperfusion injury, we examined the effect of SA on reperfusion-induced arrhythmias and postischemic ventricular dysfunction. Isolated rat hearts perfused by the Langendorff technique were preperfused with Krebs-Henseleit buffer containing SA for 10 min. Hearts were then made ischemic for 30 min, followed by 30 min of reperfusion. In a separate group, SA was administered only at the onset of reperfusion. The left ventricular contractile functions, left ventricular developed pressure (LVDP) and its first derivative (LV dP/dt), coronary flow (CF), and creatine kinase (CK) release were determined before and after ischemia. Epicardial electrocardiogram (ECG) was also recorded to analyze the incidence of ventricular tachycardia (VT) and ventricular fibrillation (VF). SA improved LVDP, LV dp/dt, and CF recovery and reduced CK release compared to the control group. The incidence of VT and VF during reperfusion was also significantly reduced by SA. Analysis of tissue thiobarbituric acid-reactive products indicates that SA decreased oxidative stress during reperfusion. In conclusion, these results suggest that SA reduces myocardial reperfusion injury and attenuates ventricular arrhythmias by trapping OH. radicals upon reperfusion in isolated rat hearts.

Protection of ischemic heart from reperfusion injury by myo-inositol hexaphosphate, a natural antioxidant

Myo-inositol hexaphosphate (phytic acid), a highly charged antioxidant, has been found to chelate metal ions such as iron and calcium and to scavenge hydroxyl radicals, .OH. This study examined the efficacy of this antioxidant and redox agent in attenuating myocardial reperfusion injury. Sprague-Dawley rats were injected intravenously with three different doses of phytic acid (group 1, saline solution only, control; group 2, 1.5 mg/100 g; group 3, 7.5 mg/100 g; group 4, 15 mg/100 g) 30 minutes before excision of hearts. Isolated hearts were prepared by the Langendorff technique. Global ischemia was induced for 30 minutes, followed by 30 minutes of reperfusion. As expected, in group 1, reperfusion was associated with enhanced creatine kinase release, reduced coronary flow, poor recovery of ventricular function as evidenced by reduced left ventricular developed pressure and the first derivative of left ventricular pressure, and increased lipid peroxidation. Groups 3 and 4, but not group 2, demonstrated myocardial protection as evidenced by reduced creatine kinase release, improved left ventricular function and coronary flow, and decreased lipid peroxidation compared with the control group. These results suggest that potential use of this antioxidant in salvaging the heart from ischemic and reperfusion injury.

Preservation of membrane phospholipids by propranolol, pindolol, and metoprolol: a novel mechanism of action of beta-blockers

In this study, we examined the effects of three different beta-blockers, propranolol, pindolol, and metoprolol, on membrane phospholipid preservation in the ischemic and reperfused rat heart. Isolated rat hearts were perfused with Krebs-Henseleit bicarbonate buffer by the Langdendorff technique in the presence or absence of propranolol, pindolol, or metroprolol (20 microM each) for 15 mins at 37 degrees C. Hearts where then either made ischemic alone at 37 degrees C for 30 mins, or followed by 30 mins of reperfusion. Coronary flow and perfusate creatine kinase content were monitored during both pre- and post-ischemic periods. At the end of the experiment, hearts were frozen by freeze-clamping at liquid nitrogen temperature. Membrane phospholipids, fatty acid composition of these phospholipids, non-esterified free fatty acids, and myocardial thiobabituric acid (TBA) reactive product were examined in these hearts. The beta-blocker-treated hearts exhibited significantly less lipid peroxidation than the control hearts (P less than 0.05), as indicated by decreased formation of TBA reactive product and the higher percentage of unsaturated fatty acids in the phosphatidylcholine (PC) in heart. In addition, compared to the control group, less accumulation of free fatty acids was observed in the propranolol and pindolol treated groups. Finally, reduced myocardial creatine kinase release and enhanced recovery of coronary flow indicated significant myocardial preservation by these beta-blockers. The efficacy of these beta-blockers were in the following order: propranolol, pindolol, metoprolol. These results suggest that beta-blockers could also protect an ischemic heart from reperfusion injury by preserving the membrane phospholipids.

Role of phospholipases A2 and C in myocardial ischemic reperfusion injury

We investigated the role of phospholipase A2 (PLA2) and phospholipase C (PLC) in myocardial phosholipid degradation and cellular injury during reperfusion of ischemic myocardium. For this purpose, isolated rat hearts were perfused with isotopic arachidonic acid to label its membrane phospholipids. Hearts preperfused with antiphospholipase A2 (anti-PLA2) retained a significantly higher amount of radiolabel in phosphatidylcholine and phosphatidylinositol and a corresponding lower amount of radiolabel in lysophosphatidylcholine and nonesterified fatty acids (P less than 0.05) after 30 min of reperfusion following 30 min of normothermic global ischemia compared with hearts preperfused with nonimmune immunoglobulin G. In similar experiments, antiphospholipase C (anti-PLC)-treated hearts were associated with significantly (P less than 0.05) higher radiolabel in all phospholipids and lower radiolabel in diacyglycerol compared with nonimmune immunoglobulin G-treated hearts. Measurement of phospholipase activity in subcellular organelles of these hearts showed decreased PLA2 activity in cytosol, mitochondria, and microsomes of anti-PLA2-treated hearts and decreased PLC activity of microsomes in anti-PLC-treated hearts. Furthermore, both the antiphospholipases attenuated the release of creatine kinase and lactate dehydrogenase into perfusate and increased contractility as well as coronary flow in the reperfused hearts. Results of this study suggest that both PLA2 and PLC are involved in the degradation of phospholipids and cellular injury that occur during reperfusion of ischemic myocardium.

High-performance liquid chromatographic detection of hydroxylated benzoic acids as an indirect measure of hydroxyl radical in heart: its possible link with the myocardial reperfusion injury

The present report describes a method suitable for the indirect assay of hydroxyl radical (OH.), which is likely to be produced during reperfusion of ischemic myocardium. Isolated rat heart perfused by the Langendorff technique was subjected to 30 min of ischemia, followed by 30 min of reperfusion. Salicylic acid (2 mM) was added to the perfusion circuit to trap any OH. radical generated during the experiment. 2,5- and 2,3-dihydroxybenzoic acids (hydroxylated products of salicylic acid) were identified by authentic standards as well as by pure OH.-generating system using high-performance liquid chromatography with electrochemical detection. In addition to serving as a chemical trap for the detection of OH., salicylate attenuated myocardial reperfusion injury as evidenced by reduced formation of creatine kinase, decreased lipid peroxidation, and improved myocardial contractile functions during reperfusion. These results thus provide direct evidence for the presence of OH. in heart and link it to the myocardial reperfusion injury.

Role of iron on membrane phospholipid breakdown in ischemic-reperfused rat heart

Oxygen-derived free radicals have been implicated in causing degradation of myocardial membrane phospholipids associated with ischemia and reperfusion. Since iron is known to catalyze the hydroxyl radical formation responsible for cellular injury, this study was designed to relate the role of iron with phospholipid breakdown in ischemic-reperfused heart. Isolated rat heart perfused by the Langendorff technique was subjected to 30 min of normothermic ischemia followed by 30 min of reperfusion. The experimental group received 0.6 mM deferoxamine, an iron chelator, before reperfusion of ischemic myocardium. Deacylation and reacylation of membrane phospholipids were monitored by using [14C]arachidonic acid (AA), whereas the de novo phospholipid synthesis was evaluated by using [3H]glycerol in the perfusate. In the deferoxamine group, the loss of [14C]phosphatidylcholine (PC) and the corresponding accumulation of isotopic lysophosphoglycerides as well as AA was significantly lower compared with the control. The incorporation of radioactivity for [14C]AA and [3H]glycerol into phospholipids was significantly increased in the treated group compared with the untreated group. In addition, decreased malonaldehyde formation and lactate dehydrogenase release, a higher recovery of high-energy phosphate compounds, and myocardial contractility were noticed in the deferoxamine-treated hearts. These results indicated that postischemic administration of an iron chelator such as deferoxamine can preserve membrane phospholipids and reduce myocardial dysfunction associated with reperfusion of ischemic heart.

Detection of hydroxyl radical in the mitochondria of ischemic-reperfused myocardium by trapping with salicylate

Although the presence of free radicals has been indicated in ischemic-reperfused heart, the exact nature and source of these free radicals are not known. The present study utilized a chemical trap, salicylic acid, to trap hydroxyl radical which could be detected as hydroxylated benzoic acid using high pressure liquid chromatography. Since the hydroxylated product is extremely stable, heart was subjected to subcellular fractionation after ischemia and reperfusion, and each fraction was separately examined for the presence of hydroxyl radical. The results indicated for the first time the presence of hydroxyl radical in the mitochondrial fraction during early reperfusion, which decreased in intensity as the reperfusion progressed.