A Novel Ultrafiltrate Extract of Propolis Exerts Anti-inflammatory Activity through Metabolic Rewiring

Thousands of years ago, humans started to use propolis because of its medicinal properties, and modern science has successfully identified several bioactive molecules within this resinous bee product. However, a natural propolis extract which has been removed the adhesive glue and preserved propolis bioactive compounds is urgently needed to maximise the therapeutic opportunities. In this study, a novel ultrafiltrate fraction from Brazilian green propolis, termed P30K, was demonstrated with anti-inflammatory properties, both in vitro and in vivo. Total flavonoids and total phenolic acids content in P30K were 244.6 mg/g and 275.8 mg/g respectively, while the IC50 value of inhibition of cyclooxygenase-2 (COX-2) was 8.30 μg/mL. The anti-inflammatory activity of P30K was furtherly corroborated in experimental models of lipopolysaccharides (LPS)-induced acute liver and lung injury. Mechanistically, integrated GC-MS and LC-MS based serum metabolomics analysis revealed that P30K modulated citrate cycle (TCA), pyruvate, glyoxylate and dicarboxylate metabolism pathways to inhibit secretion of pro-inflammatory cytokines. Results of network pharmacology and molecular docking suggested that P30K targeted catechol-O-methyltransferases (COMT), 11β-hydroxysteroid dehydrogenases (HSD11B1), and monoamine oxidases (MAOA and MAOB) to promote cellular metabolomic rewiring. Collectively, our work reveals P30K as an efficient therapeutic agent against inflammatory conditions and its efficacy is related to metabolic rewiring.

[Mid-term efficacy of China Net Childhood Lymphoma-mature B-cell lymphoma 2017 regimen in the treatment of pediatric Burkitt lymphoma]

Objective: To analyze the clinical characteristics of children with Burkitt lymphoma (BL) and to summarize the mid-term efficacy of China Net Childhood Lymphoma-mature B-cell lymphoma 2017 (CNCL-B-NHL-2017) regimen. Methods: Clinical features of 436 BL patients who were ≤18 years old and treated with the CNCL-B-NHL-2017 regimen from May 2017 to April 2021 were analyzed retrospectively. Clinical characteristics of patients at disease onset were analyzed and the therapeutic effects of patients with different clinical stages and risk groups were compared. Survival analysis was performed by Kaplan-Meier method, and Cox regression was used to identify the prognostic factors. Results: Among 436 patients, there were 368 (84.4%) males and 68 (15.6%) females, the age of disease onset was 6.0 (4.0, 9.0) years old. According to the St. Jude staging system, there were 4 patients (0.9%) with stage Ⅰ, 30 patients (6.9%) with stage Ⅱ, 217 patients (49.8%) with stage Ⅲ, and 185 patients (42.4%) with stage Ⅳ. All patients were stratified into following risk groups: group A (n=1, 0.2%), group B1 (n=46, 10.6%), group B2 (n=19, 4.4%), group C1 (n=285, 65.4%), group C2 (n=85, 19.5%). Sixty-three patients (14.4%) were treated with chemotherapy only and 373 patients (85.6%) were treated with chemotherapy combined with rituximab. Twenty-one patients (4.8%) suffered from progressive disease, 3 patients (0.7%) relapsed, and 13 patients (3.0%) died of treatment-related complications. The follow-up time of all patients was 24.0 (13.0, 35.0) months, the 2-year event free survival (EFS) rate of all patients was (90.9±1.4) %. The 2-year EFS rates of group A, B1, B2, C1 and C2 were 100.0%, 100.0%, (94.7±5.1) %, (90.7±1.7) % and (85.9±4.0) %, respectively. The 2-year EFS rates was higher in group A, B1, and B2 than those in group C1 (χ²=4.16, P=0.041) and group C2 (χ²=7.21, P=0.007). The 2-year EFS rates of the patients treated with chemotherapy alone and those treated with chemotherapy combined with rituximab were (79.3±5.1)% and (92.9±1.4)% (χ²=14.23, P<0.001) respectively. Multivariate analysis showed that stage Ⅳ (including leukemia stage), serum lactate dehydrogenase (LDH)>4-fold normal value, and with residual tumor in the mid-term evaluation were risk factors for poor prognosis (HR=1.38,1.23,8.52,95%CI 1.05-1.82,1.05-1.43,3.96-18.30). Conclusions: The CNCL-B-NHL-2017 regimen show significant effect in the treatment of pediatric BL. The combination of rituximab improve the efficacy further.

[Multicenter clinical study on the diagnosis and treatment of childhood renal tumor]

Objective: To summarize the effect of Chinese Children's Cancer Group (CCCG) Wilms tumor (WT)-2015 protocol. Methods: This was a prospective study. CCCG-WT-2015 protocol was revised on the basis of the CCCG-WT-2009 protocol. Clinical data of 288 children diagnosed with newly diagnosed kidney neoplasms in fourteen pediatric centers between September 2015 to December 2018 were summarized. The age of onset, distribution of pathological subtypes, staging, curative effect and prognostic factors of these children were analyzed. Kaplan-Meier method was used for survival curve and Log-Rank method was used for univariate analysis. Results: Among 288 cases with kidney neoplasms, there were 261 cases of WT, including 254 cases (97.3%) with favorable histology (FH) WT and 7 cases (2.7%) with unfavorable histology WT (UFHWT). The 3 year events free survival (EFS) rate for FHWT and UFHWT were (88.9±2.1)% and (80.0±17.9)%, which were better than that in WT-2009 (81.2% and 71.7%). In the 96 cases of stage Ⅲ/Ⅳ FHWT with indications for radiotherapy, 76 cases received radiation, another 20 cases received M protocol chemotherapy (cyclophosphamide, etoposide, gentamycin, vincristine and adriamycin) instead of radiation. The 3 year EFS rate for these two groups were (84.7±4.3)% and (84.7±8.1)%(χ²=0.015, P=0.902). There were 22 renal clear cell sarcoma and 5 malignant rhabdoid tumor, 3 year EFS rate of them was (94.4±5.4)% and (20.0±17.9)%. Univariate analysis was performed for age, gender, pathological type, stage, whether rupture occurred during operation, whether complete remission (CR) occurred at the end of treatment and radiotherapy. Pathological types (χ²=44.329,P<0.01) and failure to achieve CR at the end of the treatment (χ²=49.459,P<0.01) were independent factor for predicting survival. Conclusion: Compared with CCCG-WT-2009, treatment of renal tumors in CCCG-WT-2015 study yielded good survival outcome, which can be further applied.

[Analysis on the spatial-temporal characteristics of hand-foot-mouth disease in Shaanxi province, 2009-2013]

Objective: To study the spatial-temporal dynamical features of hand-foot-mouth disease (HFMD) in Shaanxi Province, so as to provide evidence for the development of relative prevention and control programs on HFMD. Methods: Surveillance data of HFMD was collected from the China Information System for Diseases Control and Prevention from 2009 to 2013. Related data on population and gross domestic product (GDP) was obtained from Shaanxi Statistical Yearbook. Statistical tools as R3.4.1, ArcGIS 10.2 and SaTScan 9.2 software were used to describe the spatial-temporal distribution of the disease. Power-law method on spatial-temporal-multicomponent model was used to analyze the spatial-temporal evolution of the HFMD epidemics in Shaanxi Province. Results: A total of 229 904 cases of HFMD were reported in Shaanxi Province from 2009 to 2013, with an average annual incidence as 122.50 per 100 000. Obvious seasonal characteristics were noticed, with 71.71% of the total cases identified between April and July. Counties with high incidence were mainly distributed in the mid-and east parts of Guanzhong area. Through temporal and spatial scan statistics, we identified that ClassⅠ clustering area was fixed to the central and southeast regions of Shaanxi province which were around Xi'an City between 2009 and 2013, with the relative risk (RR) as 2.24, ranging from 2.18 to 3.08. Results from Power-law analysis showed that the continuous follow-up impact from the previous HFMD epidemics appeared strong in Tongguan, Pucheng districts of Weinan City and Weiyang district of Xi'an, with autoregressive components as 1.14, 0.97 and 0.89, respectively. The risk of HFMD seemed high in Huayin city, Changan and Yanta districts and with the endemic components as 5.08, 4.12 and 4.08, respectively. Impact of the epidemics on nearby districts was largely seen in Lianhu district of Xi'an, Wugong district of Xianyang and Gaoling district of Xi'an with epidemic components as 2.12, 2.08 and 1.77, respectively. The etiological constituents of HFMD were mainly Enterovirus 71 between 2009 and 2012, while HFMD was mainly caused by other entero-viruses, in 2013. Conclusion: Significant spatial-temporal heterogeneity of HFMD was seen in Shaanxi province, which called for specific strategies to be developed in the highly endemic areas.

[Long-term results of multicenter study based on childhood acute lymphoblastic leukemia 2005 protocol]

Objective: To evaluate the long-term efficacy and prognostic factors of childhood acute lymphoblastic leukemia (ALL) enrolled in Shanghai Children's Medical Center-Acute Lymphoblastic Leukemia-2005(SCMC-ALL-2005) multicenter study. Methods: Between May 2005 and December 2014, 1 497 newly diagnosed ALL patients were enrolled and treated in 5 hospitals of SCMC-ALL-2005 study group, using risk-stratified SCMC-ALL-2005 protocol. Risk group classification and treatment intensity were based on clinical features, genetic abnormalities, early response to treatment and levels of minimal residual disease (MRD). Kaplan-Meier method was used to generate overall survival (OS) and event-free survival(EFS) curves. Cox proportional hazards models were used for multivariate analyses. Results: The patients were followed up to December 31, 2016, the median follow-up time was 69 months (24-141 months). The 5-year and 10-year OS rates were (80.0±1.0)% and (76.0±2.0)%. The 5-year and 10-year EFS rates were (69.0±1.0)% and (66.0±2.0)%. The 5-year and 10-year relapse rates were (23.0±1.0)% and (25.0±2.0)%. The 5-year OS and EFS for low risk (LR), intermediate risk (IR) and high risk (HR) were (91.1±1.4)% and (83.3±1.8)%, (79.2±1.5)% and (68.9±1.7)%, (52.9±4.4)% and (30.0±3.8)%, respectively. MRD negative status (<0.01%) on day 55 was seen in 792 patients (82.8%) and positive MRD on day 55 was associated with poor prognosis (OR=1.9, 95%CI: 1.3-2.7, P=0.001). Twenty-four HR patients received allogeneic hematopoietic stem cell transplantation and 17(70.8%) of them were alive and in remission. A total of 164 severe adverse events occurred, 46 of them died, treatment-related mortality was 3.1%. Conclusions: In this large sample research, the overall outcome for multi-center SCMC-ALL-2005 study was favorable. This helps to promote the standardized treatment of childhood ALL to the whole country. MRD results on day 55 of induction therapy have important prognostic and therapeutic implications.

Effect of propolis on preserving human periodontal ligament cells and regulating pro-inflammatory cytokines

BACKGROUND/AIM

Propolis has been suggested as a storage medium for avulsed teeth. The aim of this study was to compare the effectiveness of Brazilian propolis with Hank's balanced salt solution and milk in maintaining the viability of human periodontal ligament cells, their osteogenic differentiation potential, and pro-inflammatory cytokine expression.

MATERIAL AND METHODS

Cell Counting Kit 8 assays were performed to test human periodontal ligament cell viability in different storage media. The preservative effect on osteogenic differentiation was evaluated using alkaline phosphatase staining and activity assays, Alizarin Red S staining, and western blotting. Quantification of pro-inflammatory cytokines was performed using real-time PCR and enzyme-linked immunosorbent assays.

RESULTS

Brazilian propolis at 10 μg/ml was not cytotoxic toward human periodontal ligament cells. The milk group showed the highest cell viability. Brazilian propolis and Hank's balanced salt solution groups showed similar cell viabilities. Alkaline phosphatase staining and activity were similar in all groups. Calcium deposition and mineralization nodule formation were similar in the Brazilian propolis and Hank's balanced salt solution groups, but were higher in the milk group. Osteogenic marker gene and protein levels were similar in all groups. The genes and protein expression levels of IL1β, IL6, and IL8 decreased significantly after treatment with Brazilian propolis. TNFα mRNA expression showed no significant difference among the experimental groups. Pro-inflammatory cytokine levels in the milk group were higher than in the Brazilian propolis and Hank's balanced salt solution groups.

CONCLUSIONS

Brazilian propolis, Hank's balanced salt solution, and milk maintained the viability of human periodontal ligament cells and preserved their osteogenic differentiation ability similarly. However, Brazilian propolis showed a better anti-inflammatory effect. This article is protected by copyright. All rights reserved.

[Eccrine angiomatous hamartoma: a clinicalopathologic analysis of 4 cases]

OBJECTIVE

To investigate the clinical and histopathologic features, diagnosis and differential diagnosis of eccrine angiomatous hamartoma(EAH).

METHODS

Four cases of eccrine angiomatous hamartoma were studied by light microscopy and immunohistochemical staining along with review of the literature.

RESULTS

There were 3 male and 1 female patients at diagnosis in age of 4 months, 3.5 years, 5.5 years and 14.0 years, respectively. Tumor sites included the left little finger (1 case), right index finger (1 case), lower back (1 case) and knee (1 case). Clinically, most cases presented as a solitary, flesh or reddish papule, plaque or nodule with size of 0.4-6.0 cm in diameter. The skin lesions in 3 cases enlarged commensurate with the growth of the patients, and local hyperhidrosis in one case. Histologically, EAH was characterized by proliferation of well-differentiated eccrine secretory and ductal elements closely associated with thin-walled angiomatous channels in the middle or deep dermis and subcutaneous tissue. By immunohistochemistry, the vascular components were positive for CD31, CD34 and factor Ⅷ related antigen while the eccrine glands were positive for S-100 protein, CEA, EMA, CAM5.2 and GCDFP15. Local surgical resection was performed in 4 cases and follow-up data (0.5 to 4.5 years) showed no recurrence.

CONCLUSION

EAH is a rare, benign cutaneous hamartoma. Combination of clinical manifestations, histological changes and immunohistochemical findings is useful for the diagnosis and differential diagnosis.

Treatment outcome of rhabdomyosarcoma in Hong Kong Chinese children

OBJECTIVES

To review the treatment outcome of rhabdomyosarcoma in Hong Kong Chinese children.

DESIGN

Retrospective review.

SETTING

University teaching hospital, Hong Kong.

PATIENTS

Consecutive cases of rhabdomyosarcoma diagnosed and treated by the Department of Paediatrics and Adolescent Medicine of Queen Mary Hospital between 1989 and 2005. Each patient was staged and treated according to the Intergroup Rhabdomyosarcoma Study guidelines.

MAIN OUTCOME MEASURES

Overall and event-free survival rates, and toxicity data.

RESULTS

Of 19 patients (8 males and 11 females), 14 (74%) were younger than 10 years old. The median age at diagnosis was 6 (range, 0.5-17) years. Primary sites of rhabdomyosarcoma included: the head and neck (n=8; 6 classified as cranial parameningeal), genitourinary (3), extremity (3), pelvis (3), and trunk (2). Thirteen (68%) had embryonal and six (32%) had alveolar histology. Two, 2, 9, and 6 were classified as belonging to Intergroup Rhabdomyosarcoma Study groups 1, 2, 3, and 4, respectively. Respective 5-year overall and event-free survival rates of the entire cohort were 49% (95% confidence interval, 26-73%) and 32% (10-55%), with a median follow-up of 3.4 (range, 0.2-16.7) years. In non-metastatic cases (Intergroup Rhabdomyosarcoma Study groups 1-3), the 5-year overall survival rate was 66% (95% confidence interval, 39-93%) and in metastatic cases (group 4) it was 17% (0-46%). The 5-year overall survival rate for patients aged less than 10 years was 60% (95% confidence interval, 33-87%) compared to 20% (0-55%) in those aged 10 years and over. Significant treatment-related toxicities including myelosuppression, infections, peripheral neuropathy, and second cancers were encountered.

CONCLUSIONS

Treatment outcome of rhabdomyosarcoma in this cohort of Chinese children was less favourable than that reported in international studies. Whilst the main reason could have been related to the high proportion of metastatic cases, also non-metastatic cases faired worse. Improved outcomes may be achieved by advances in multidisciplinary (paediatric oncology, pathology, radiotherapy, and surgery) management and supportive care.

Cytogenetic localization of the growth and reproduction complex (Grc) in the rat and in the mouse and its position in relation to RT1.EC and other loci in the rat MHC

The segment of rat chromosome 20 (RNO20p12) that contains the classical loci of the major histocompatibility complex (MHC; RT1.A-RT1.E) also contains genes affecting growth, reproduction and susceptibility to chemical carcinogens (the Grc) and multiple genes encoding class I MHC antigens (the EC region). The relative positions of the MHC, Grc, and EC region have not been demonstrated explicitly, although they have been postulated from genetic mapping studies. The present study was undertaken to map these regions cytogenetically by several different approaches using cosmids specific for the Rps 18, Hspa1 and Bat1 genes. The order was shown to be: centromere-Rps 18-Hspa1-Bat1-EC-Grc.

Evidence for regulation of the PTEN tumor suppressor by a membrane-localized multi-PDZ domain containing scaffold protein MAGI-2

PTEN is a tumor suppressor gene mutated in human cancers. Although many mutations target the phosphatase domain, others create a truncated protein lacking the C-terminal PDZ-binding motif or a protein that extends beyond the PDZ-binding motif. Using the yeast two-hybrid system, we isolated a membrane-associated guanylate kinase family protein with multiple PDZ domains [AIP-1 (atrophin interacting protein 1), renamed MAGI-2 (membrane associated guanylate kinase inverted-2)]. MAGI-2 contains eight potential protein-protein interaction domains and is localized to tight junctions in the membrane of epithelial cells. PTEN binds to MAGI-2 through an interaction between the PDZ-binding motif of PTEN and the second PDZ domain of MAGI-2. MAGI-2 enhances the ability of PTEN to suppress Akt activation. Furthermore, certain PTEN mutants have reduced stability, which is restored by adding the minimal PDZ-binding motif back to the truncated protein. We propose that MAGI-2 improves the efficiency of PTEN signaling through assembly of a multiprotein complex at the cell membrane.

Biological effects of genes in the Grc and EC region of the rat major histocompatibility complex

PROBLEM

To study the mechanism of action of major histocompatibility complex (MHC)-linked genes affecting reproduction, growth, and susceptibility to chemical carcinogens.

METHOD OF STUDY

Tumors derived from rat embryonic fibroblasts were transfected with cosmids from the Grc and its linked regions, the unrelated A region, and a nonMHC region, or with genes from the Grc, Grc-linked, and nonMHC regions, to determine whether they could suppress tumor growth as determined by in vitro (soft agar) and in vivo assays.

RESULTS

Tumor fibroblasts transfected with cosmids from the Grc or from the EC region decreased tumor growth in both the in vitro and in vivo assays. Transfection with individual genes from the Grc had no effect on tumor growth in either assay.

CONCLUSIONS

The effects of the Grc on reproduction, growth, and tumorigenesis are mediated by extended genetic effects, i.e., by the conformation of the DNA in this region. Similar effects were seen following transfection with cosmids from the Grc-linked EC region, and this finding strengthens the hypothesis that the conformation of the DNA in this general region is critical for its function. A similar effect has been described for the locus control region (LCR) in the beta-globin gene family in the human.

Molecular basis and function of voltage-gated K+ channels in pulmonary arterial smooth muscle cells

K(+)-channel activity-mediated alteration of the membrane potential and cytoplasmic free Ca2+ concentration ([Ca2+]cyt) is a pivotal mechanism in controlling pulmonary vasomotor tone. By using combined approaches of patch clamp, imaging fluorescent microscopy, and molecular biology, we examined the electrophysiological properties of K+ channels and the role of different K+ currents in regulating [Ca2+]cyt and explored the molecular identification of voltage-gated K+ (KV)- and Ca(2+)-activated K+ (KCa)-channel genes expressed in pulmonary arterial smooth muscle cells (PASMC). Two kinetically distinct KV currents [IK(V)], a rapidly inactivating (A-type) and a noninactivating delayed rectifier, as well as a slowly activated KCa current [IK(Ca)] were identified. IK(V) was reversibly inhibited by 4-aminopyridine (5 mM), whereas IK(Ca) was significantly inhibited by charybdotoxin (10-20 nM). K+ channels are composed of pore-forming alpha-subunits and auxiliary beta-subunits. Five KV-channel alpha-subunit genes from the Shaker subfamily (KV1.1, KV1.2, KV1.4, KV1.5, and KV1.6), a KV-channel alpha-subunit gene from the Shab subfamily (KV2.1), a KV-channel modulatory alpha-subunit (KV9.3), and a KCa-channel alpha-subunit gene (rSlo), as well as three KV-channel beta-subunit genes (KV beta 1.1, KV beta 2, and KV beta 3) are expressed in PASMC. The data suggest that 1) native K+ channels in PASMC are encoded by multiple genes; 2) the delayed rectifier IK(V) may be generated by the KV1.1, KV1.2, KV1.5, KV1.6, KV2.1, and/or KV2.1/KV9.3 channels; 3) the A-type IK(V) may be generated by the KV1.4 channel and/or the delayed rectifier KV channels (KV1 subfamily) associated with beta-subunits; and 4) the IK(Ca) may be generated by the rSlo gene product. The function of the KV channels plays an important role in the regulation of membrane potential and [Ca2+]cyt in PASMC.

Roles of K+ and Cl- channels in cAMP-induced pulmonary vasodilation

Increase in intracellular adenosine 3', 5'-cyclic monophosphate (cAMP) is a common pathway for many clinically used drugs to cause pulmonary artery (PA) relaxation. Activity of sarcolemmal K+ and Cl(-)-channels is an important determinant of membrane potential (Em), which, in turn, plays a critical role in regulating pulmonary vascular tone. Whether K+ and Cl- channels were involved in cAMP-induced PA relaxation was tested using isolated rat PA rings. Raising extracellular K+ concentration from 20 to 142.7 mM increased the K(+)-evoked contraction, but significantly decreased the relaxation induced by the adenylate cyclase activator, forskolin (FSK, 2.5 microM), suggesting that FSK-induced PA relaxation depended on transmembrane K+ gradient. Indeed, the FSK-induced relaxation was inhibited by 4-aminopyridine (4-AP, 10 mM), a voltage-gated K+ (Kv) channel blocker. Neither the Ca(2+)-activated K+ channel blocker, charybdotoxin, nor the ATP-sensitive K+ channel blocker, glibenclamide, had this effect. Furthermore, reducing extracellular Cl- concentration from 142.7 to 50 mM significantly decreased the FSK-induced relaxation in PA rings precontracted with 142.7 mM K+ (Ek approximately 0 mV), but negligibly affected the evoked contraction. This indicates that transmembrane Cl- gradient also regulates FSK-induced PA relaxation. Indeed, the Cl- channel blocker, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB, 10 microM), significantly inhibited the FSK-induced relaxation in PA rings preconstricted by 142.7 mM K+. In summary, the data suggest that the cAMP-induced PA relaxation is attributable, at least partly, to both activation of the 4-AP-sensitive Kv channels and stimulation of the NPPB-sensitive Cl- channels.

Hypoxia inhibits gene expression of voltage-gated K+ channel alpha subunits in pulmonary artery smooth muscle cells

Activity of voltage-gated K+ channels (KV) in pulmonary arterial smooth muscle cells (PASMC) is pivotal in controlling membrane potential, cytoplasmic free Ca2+ concentration ([Ca2+]cyt, and pulmonary vasomotor tone. Acute hypoxia selectively inhibits KV channels, depolarizes PASMC, raises [Ca2+]cyt, and causes pulmonary vasoconstriction and vascular remodeling. Prolonged hypoxia (24-60 h) decreased significantly the mRNA levels of KV channel alpha subunits, KV1.2 and KV1.5. Consistently, the protein levels of KV1.2 and KV1.5 were also decreased significantly by hypoxia (48-72 h). Nevertheless, hypoxia affected negligibly the mRNA levels of KV channel beta subunits (KVbeta1, KVbeta2, and KVbeta3). The native K+ channels are composed of pore-forming alpha and auxiliary beta subunits. Assembly of KV beta subunits with alpha subunits confers rapid inactivation on the slowly or non-inactivating delayed rectifier KV channels. KV beta subunits also function as an open-channel blocker of KV channels. Thus, the diminished transcription and expression of KV alpha subunits may reduce the number of KV channels and decrease KC currents. Unchanged transcription of KV beta subunits may increase the fraction of the KV channel alpha subunits that are associated with beta subunits and further reduce the total KV currents. These data demonstrate a novel mechanism by which chronic hypoxia may cause pulmonary vasoconstriction and hypertension.

Immunogenetic and oncogenic properties of rat trophoblast cell lines

PROBLEM

The nature of major histocompatibility complex (MHC) antigen expression on rat placentas, trophoblast cell lines, and tumors derived from trophoblast cells was explored.

METHOD OF STUDY

Cytohistochemical and flow cytometric analysis and molecular techniques.

RESULTS

MHC antigen expression and genomic imprinting on the placenta and on trophoblast cells varies with the time of gestation and with the type of MHC antigen.

CONCLUSIONS

There is no correlation in trophoblast cells between class I expression and cell ploidy, on the one hand, and malignant potential, on the other hand. Genomic imprinting of class I antigens in the rat placenta is a quantitative phenomenon.

Recent studies on the structure of the grc region in the rat

PROBLEM

To explore the nature of the genes in the grc.

METHOD

Chromosome walking of the grc and sequencing new genes.

RESULTS

The RT1.O,N genes have been aligned, and two new types of genes, RT1.S1,2 and Rprl,2,3, have been discovered and mapped. An extensive physical map of the grc region is presented.

CONCLUSION

The disease associations in both the rat and the human appear to cluster in two regions that map in approximately the same place in both species, given the translocation that occurred in the major histocompatibility complex (MHC) of the rat relative to the MHC of the human.

Role of calcium-activated chloride current in regulating pulmonary vasomotor tone

Many agonists induce vasoconstriction by releasing intracellularly stored Ca2+ and promoting Ca2+ influx. Activation of Ca(2+)-activated Cl- (ClCa) channels may be a critical mechanism by which a rise in intracellular free Ca2+ concentration ([Ca2+]i) causes membrane depolarization that serves to sustain the elevated [Ca2+]i and maintain vascular tone. In this study the biophysical and pharmacological properties of ClCa currents [ICKCa] were characterized in rat pulmonary artery (PA) smooth muscle cells, and their relationship to the regulation of pulmonary vascular tone was determined. When K+ currents were eliminated by using Cs(+)-containing internal solution, depolarization elicited an inward Ca2+ current followed by a time-dependent outward Cl- current that reversed near Cl- equilibrium potential. Repolarizing voltage steps produced a large inward tail Cl- current that also reversed at a potential close to Cl- equilibrium potential. Replacement of extracellular Ca2+ with Ba2+ significantly augmented the Ca2+ current but abolished the Cl- currents. The Cl- channel blocker niflumic acid (10-50 microM) diminished the time-dependent outward Cl- current and the inward tail Cl- current, decreased serotonin-induced membrane depolarization, and inhibited agonist-induced PA contraction. In the absence of extracellular Ca2+, cyclopiazonic acid, which releases Ca2+ from sarcoplasmic reticulum, elicited an inward Cl- current at a holding potential of -70 mV. These results indicate that rat PA myocytes possess ClCa channels that are activated by depolarization-induced Ca2+ influx and agonist-induced Ca2+ release. This Cl- current contributes to agonist-induced pulmonary vasoconstriction via membrane depolarization.

Inhibition of K(V) and K(Ca) channels antagonizes NO-induced relaxation in pulmonary artery

Endogenous nitric oxide (NO) may contribute to the maintenance of normal pulmonary vasomotor tone, and inhaled NO is used to treat patients with pulmonary hypertension. Because pulmonary vascular tone is regulated by intracellular free Ca2+ concentration and membrane potential, which are controlled by the K+ channel activity in pulmonary artery (PA) smooth muscle cells, we sought to determine whether K+ channels are involved in NO-induced relaxation and, if so, which types of K+ channels are responsible. Authentic NO (approximately 0.3 microM) and sodium nitroprusside (SNP, 10 pM) both produced significant relaxation in isolated PA rings precontracted by increasing extracellular K+ concentration. Further elevation of the K+ concentration from 20 to 60 mM resulted in a significant increase in contraction but caused a marked decline in SNP- and NO-mediated PA relaxation. The dependence of SNP- and NO-induced relaxation on transmembrane K+ gradient suggests that K+ efflux through K+ channels is involved in these effects. Furthermore, 4-aminopyridine (4-AP, 5-10 mM), which blocks voltage-gated K+ channels (K(V)), and charybdotoxin (200 nM), which blocks Ca2+-activated K+ channels (K(Ca)), both significantly inhibited NO- and SNP-induced PA relaxation. The ATP-sensitive K+ channel blocker glibenclamide, however, had no effect on the relaxation response. The blocking of guanylate cyclase diminished, but did not abolish, the NO-induced relaxation, whereas 4-AP further decreased the NO-induced relaxant response in the presence of the guanylate cyclase inhibitor LY-83583. These data suggest that activation of both K(V) channels and K(Ca) channels by guanosine 3',5'-cyclic monophosphate-dependent and -independent pathways is a mechanism, at least in part, by which NO induces PA relaxation.

Nitric oxide inhibits serotonin-induced calcium release in pulmonary artery smooth muscle cells

Nitric oxide (NO) is a potent endothelium-derived pulmonary vasodilator. Serotonin (5-HT; 10-50 microM) constricts pulmonary artery (PA) by releasing Ca2+ from intracellular stores and promoting Ca2+ influx through Ca2+ channels in PA smooth muscle cells (PASMC). The effect of NO on 5-HT-induced increase in cytosolic free Ca2+ concentration ([Ca2+]i) in rat PASMC was investigated to elucidate whether inhibition of agonist-mediated Ca2+ rise is involved in the NO-mediated pulmonary vasodilation. The 5-HT-induced increase in [Ca2+]i was characterized by a transient (because of Ca2+ release from intracellular stores) followed by a plateau (because of Ca2+ influx). Removal of extracellular Ca2+ eliminated the 5-HT-induced [Ca2+]i plateau, but insignificantly affected the [Ca2+]i transient. In some of the PASMC bathed in the Ca(2+)-containing or Ca(2+)-free solution, 5-HT also induced Ca2+ oscillations. Pretreatment of the cells with 10 microM cyclopiazonic acid (CPA) abolished, whereas 10 mM caffeine negligibly affected, the 5-HT-induced [Ca2+]i transients in the absence of external Ca2+. Authentic NO (approximately 0.3 microM) reversibly diminished 5-HT-induced [Ca2+]i transients but augmented CPA-induced Ca2+ release in the absence of extracellular Ca2+. NO also significantly inhibited 5-HT-induced [Ca2+]i plateau in PASMC bathed in Ca(2+)-containing solution, suggesting that NO inhibits both agonist-induced Ca2+ release from the CPA-sensitive Ca2+ stores and Ca2+ influx from extracellular fluid. These data suggest that NO-induced inhibition of the evoked increases in [Ca2+]i and augmentation of Ca2+ sequestration into intracellular stores in PASMC are involved in the mechanisms by which NO causes pulmonary vasodilation.

Pulmonary vasoconstrictor effects of prostacyclin in rats: potential role of thromboxane receptors

Endogenous prostacyclin (PGI2; epoprostenol) is a potent endothelium-derived pulmonary vasodilator. However, the effects of exogenous PGI2 on isolated arteries could be either relaxant or contractile, depending on the species and organ studied. The present study investigated the distal pathways involved in the PGI2-induced contraction in rat intrapulmonary artery (PA) and relaxation in lamb PA. When vessels were precontracted with 30 mM K+, PGI2 (1 microM) induced relaxation in lamb PA but caused contraction in rat PA. Use of 30 mM K+, phenylephrine, serotonin, angiotensin II, or hypoxia to precontract the vessels did not alter the contractile effect of PGI2 in rat PA. Nevertheless, PGI2 produced a mild relaxation in rat PA precontracted by U-46619, a thromboxane A2 (TxA2)-receptor agonist, whereas the TxA2-receptor blocker SQ-29548 (0.1-0.5 microM) abolished the contractile response in rat PA. These data suggest that PGI2-induced contraction is mediated by activation of TxA2 receptors. The PGI2-induced modest relaxation in rat PA, which was only observed when TxA2 receptors were blocked by SQ-29548, suggests that the PGI2-mediated vasorelaxant pathway is diminished in these vessels. Simultaneous application of forskolin, an adenylate cyclase activator, and rolipram, a phosphodiesterase inhibitor, caused similar relaxation in both rat and lamb PA. This suggests that the adenosine 3',5'-cyclic monophosphate-dependent relaxing pathway is intact in rat PA and is comparable to that in lamb PA. On the basis of these data, we conclude that the pathways responsible for the paradoxical effects of PGI2 on rat and lamb PA are located upstream of the adenosine 3',5'-cyclic monophosphate-dependent relaxing pathway and that a paucity of PGI2 receptors in rat PA may be responsible.

NO hyperpolarizes pulmonary artery smooth muscle cells and decreases the intracellular Ca2+ concentration by activating voltage-gated K+ channels

NO causes pulmonary vasodilation in patients with pulmonary hypertension. In pulmonary arterial smooth muscle cells, the activity of voltage-gated K+ (Kv) channels controls resting membrane potential. In turn, membrane potential is an important regulator of the intracellular free calcium concentration ([Ca2+]i) and pulmonary vascular tone. We used patch clamp methods to determine whether the NO-induced pulmonary vasodilation is mediated by activation of Kv channels. Quantitative fluorescence microscopy was employed to test the effect of NO on the depolarization-induced rise in [Ca2+]i. Blockade of Kv channels by 4-aminopyridine (5 mM) depolarized pulmonary artery myocytes to threshold for initiation of Ca2+ action potentials, and thereby increased [Ca2+]i. NO (approximately 3 microM) and the NO-generating compound sodium nitroprusside (5-10 microM) opened Kv channels in rat pulmonary artery smooth muscle cells. The enhanced K+ currents then hyperpolarized the cells, and blocked Ca(2+)-dependent action potentials, thereby preventing the evoked increases in [Ca2+]i. Nitroprusside also increased the probability of Kv channel opening in excised, outside-out membrane patches. This raises the possibility that NO may act either directly on the channel protein or on a closely associated molecule rather than via soluble guanylate cyclase. In isolated pulmonary arteries, 4-aminopyridine significantly inhibited NO-induced relaxation. We conclude that NO promotes the opening of Kv channels in pulmonary arterial smooth muscle cells. The resulting membrane hyperpolarization, which lowers [Ca2+]i, is apparently one of the mechanisms by which NO induces pulmonary vasodilation.

A mitochondrial uncoupler increases KCa currents but decreases KV currents in pulmonary artery myocytes

Intracellular free Ca2+ concentration ([Ca2+]i) and ATP play important roles in the regulation of K- channels in pulmonary artery (PA) myocytes. Previous studies have demonstrated that hypoxia and the metabolic inhibitor, 2-deoxy-D-glucose, decrease voltage-gated K+ (KV) currents [IK(V)] and thereby depolarize PA myocytes; these effects lead to a rise in [Ca2+]i. Here, we used carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone (FCCP), a protonophore that uncouples mitochondrial respiration from ATP production, to test whether the inhibition of oxidative phosphorylation affects K+ channel activities in rat PA myocytes. Patch-clamp and fluorescent-imaging microscopy techniques were used to measure K+ currents (IK) and [Ca2+]i, respectively. FCCP (3-5 microM) reversibly raised [Ca2-]i in the presence and absence of external Ca2+. This effect was prevented by pretreating the cells with the membrane-permeable Ca2+ chelator, 1,2-bis(2-amino-phenoxy) ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA-AM). This suggests that much of the FCCP-evoked rise in [Ca2-]i was due to Ca2+ release from intracellular stores. Brief exposure to FCCP (approximately 2 min) reversibly enhanced Ik. This augmentation was not influenced by glibenclamide, an ATP-sensitive K channel blocker, but was eliminated by pretreatment with BAPTA-AM. This implies that the FCCP-evoked rise in [Ca2+]i activated Ca(2+)-activated K- (Kca) channels. Furthermore, in BAPTA-treated cells, longer application (> or = 6 min) of FCCP reversibly decreased IK(V) in PA cells bathed in Ca(2+)-free solution. These results demonstrate that FCCP affects KCa and Kv channels by different mechanisms. FCCP increases IK[Ca] by raising [Ca2+]i primarily as a result of Ca2+ release, but decreases IK(V) by a Ca(2+)-independent mechanism, presumably the inhibition of oxidative ATP production.

Physical mapping of the E/C and grc regions of the rat major histocompatibility complex

Alignment of class I-hybridizing cosmids from an R21 (AlBlDlEugrc+) genomic DNA library gave two contigs: one [150 kilobases (kb)] encompassed the E/C region, or a large part thereof, and the other (110 kb) contained the grc region which has genes influencing resistance to chemical carcinogens (rcc), fertility (ft), and growth (dw-3). Amplification of gene sequences in the four cosmids in the E/C region using Eu-specific and LW2 (RT1.C)-specific primers showed that each cosmid contained both Eu-like and C-like genes. They are clearly different but closely associated, and they show some variation from the prototypic E (Eu) and C (LW2) genes, respectively. Comparison of DNA from grc+ and grc- strains of rats showed that the deletion in the grc- strains was approximately 50 kb, and that it was located on two of the three cosmids in the grc-region contig. The use of specific class I probes showed that the grc region contained tandemly duplicated RT1.O-RT1.N genes and that the RT.BM1 loci lay outside of the grc region. Neither contig reacted with probes specific for class II, TNFA, Hsp70, or RT1.M genes. The data presented here and the previous data in the literature (summarized in Gill et al. 1995) suggest that the gene order in the major histocompatibility complex (MHC) and MHC-linked region of the rat is: A-E/C-grc-M.

[Synergism of sobuzoxane in combination with doxorubicin against leukemia P388 in mice]

AIM

To study the antitumor activity of sobuzoxane (Sob) in combination with doxorubicin (Dox) and the effect of Sob on Dox-induced cardiotoxicity.

METHODS

DBA/2 mice bearing transplanted leukemia P388 were given i.v. Dox 2 mg.kg-1.d-1 for 3 d, 4 mg.kg-1.d-1 for 1 d combined with ig Sob 20, 40 mg.kg-1.d-1 for 7 d. The increase in life span (ILS) of each group was recorded in 30 d. The myocardium of moribund mice was examined by transmission electron microscopy.

RESULTS

The ILS of combination therapeutic groups of Sob with Dox was 48.7%, 57.3%, 59.0%, and 62.4% respectively, which were 30%-90% higher than the sum of ILS of two groups treated with Dox and Sob separately (P < 0.01). The ultrastructural injury of cardiomyocytes of P388-bearing mice caused by combination chemotherapy with Dox plus Sob was markedly attenuated compared with Dox alone.

CONCLUSION

Sob with Dox exhibited an antitumor synergistic effect on leukemia P388, and the cardiotoxicity of Dox was reduced by Sob.

Hypoxic and metabolic regulation of voltage-gated K+ channels in rat pulmonary artery smooth muscle cells

Inhibition of voltage-gated K+ (Kv) channels by 4-aminopyridine (4-AP) depolarizes pulmonary artery (PA) smooth muscle cells, induces Ca(2+)-dependent action potentials and increases [Ca2+]i. Neither charybdotoxin, which blocks Ca(2+)-activated K+ channels, nor glibenclamide, which blocks ATP-sensitive K+ channels, has such effects on membrane potential (Em) and [Ca2+]i. Hypoxia reversibly decreases the 4-AP-sensitive KV currents (IK(V)) in PA myocytes. The resulting membrane depolarization caused by decreased IK(V) induces Ca(2+)-dependent action potentials and thereby raises [Ca2+]i. Thus, KV channel activity plays a critical role in: (a) regulating Em and [Ca2+]i under physiological conditions; and (b) sensing O2 alteration and transducing the hypoxic stimulus to changes of Em and [Ca2+]i. The metabolic inhibitors 2-deoxy-D-glucose (2-DOG; 10 mM) and carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazone (FCCP; 3-5 microM), the reducing agent reduced glutathione and inhibitors of cytochrome P-450, all mimic the effects of hypoxia on IK(V) and Em in PA myocytes. Furthermore, hypoxia and 2-DOG negligibly affect IK(V) and Em in mesenteric artery smooth muscle cells. These results suggest that hypoxia, perhaps via a localized reduction of ATP, triggers the block of KV channels and depolarizes PA myocytes. This blockade may also be mediated by a change in cellular redox status, perhaps via a conformational change of a haem- (or metal-) containing regulatory moiety that is attached to the channel protein.

Inhibition of glycolysis by 2-DG increases [Ca2+]i in pulmonary arterial smooth muscle cells

Inhibition of glycolysis depolarizes single pulmonary arterial smooth muscle cells (PASMC) and potentiates hypoxic pulmonary vasoconstriction (HPV) in isolated perfused rat lungs. Whether glycolytic inhibition causes an increase in the intracellular Ca2+ concentration ([Ca2+]i) in PASMC was determined in this study. [Ca2+]i was measured in primary cultured rat PASMC using the Ca2+ -sensitive fluorescent indicator, fura 2, and quantitative fluorescence microscopy. Extracellular application of the glycolytic inhibitor, 2-deoxy-D-glucose (2-DG), significantly and reversibly increased [Ca2+]i in PASMC. Removal of extracellular Ca2+ and application of the Ca2+ channel blocker, verapamil (10 microM), attenuated, but did not eliminate, the 2-DG-induced rise in [Ca2+]i. In the absence of extracellular Ca2+, however, depletion of inositol triphosphate-sensitive intracellular Ca2+ stores by 10 microM cyclopiazonic acid (CPA) completely abolished the 2-DG-induced increase in [Ca2+]i. The data suggest that 2-DG-induced increases in [Ca2+]i result from both Ca2+ influx through the verapamil-sensitive voltage-gated Ca2+ channels and Ca2+ release from the CPA-sensitive intracellular Ca2+ stores.

Voltage-gated K+ currents regulate resting membrane potential and [Ca2+]i in pulmonary arterial myocytes

The membrane potential (Em) of pulmonary arterial smooth muscle cells (PASMCs) regulates pulmonary arterial tone by controlling voltage-gated Ca2+ channel activity, which is a major contributor to [Ca2+]i. The resting membrane is mainly permeable to K+; thus, the resting Em is controlled by K+ permeability through sarcolemmal K+ channels. At least three K+ currents, voltage-gated K+ (KV) currents, Ca(2+)-activated K+ (KCa) currents, and ATP-sensitive (KATP) currents, have been identified in PASMCs. In this study, both patch-clamp and quantitative fluorescent microscopy techniques were used to determine which kind(s) of K+ channels (KV, KCa, and/or KATP) is responsible for controlling Em and [Ca2+]i under resting conditions in rat PASMCs. When the bath solution contained 1.8 mmol/L Ca2+ and the pipette solution included 0.1 mmol/L EGTA, depolarizations (-40 to +80 mV) elicited both KCa and KV currents. Removal of extracellular Ca2+ and increase of intracellular EGTA concentration (to 10 mmol/L) eliminated the Ca2+ influx-dependent KCa current. 4-Aminopyridine (4-AP, 5 to 10 mmol/L) but not charybdotoxin (ChTX, 10 to 20 nmol/L) significantly reduced KV current under these conditions. In current-clamp experiments, 4-AP decreased Em (depolarization) and induced Ca(2+)-dependent action potentials; this depolarization increased [Ca2+]i in intact PASMCs. Neither ChTX nor the specific blocker of KATP channels, glibenclamide (2 to 10 mumol/L), caused membrane depolarization and the increase in [Ca2+]i. However, pretreatment of PASMCs with ChTX enhanced the 4-AP-induced increase in [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of cytochrome P-450 reduces voltage-gated K+ currents in pulmonary arterial myocytes

Cytochrome P-450 (P-450) is a NADPH-requiring and O2-dependent monooxygenase system. It is present in lung and has been postulated to act as an O2 sensor in hypoxic pulmonary vasoconstriction. To determine whether P-450 is involved in the regulation of voltage-gated K+ (KV) channel activity in pulmonary artery (PA) myocytes, we used the whole cell patch-clamp technique to evaluate the effects of P-450 inhibitors on KV channel currents (IKV) and membrane potential (Em). Bath application of the P-450 inhibitors clotrimazole, miconazole, and 1-aminobenzotriazole (1-ABT) significantly and reversibly inhibited steady-state IKV (IKss) and depolarized PA cells bathed in either Ca(2+)-containing (1.8 mM) or Ca(2+)-free [0.5-1 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N'N'-tetraacetic acid present] bath solution. Clotrimazole (1 microM), miconazole (10 microM), and 1-ABT (1 mM) reversibly reduced IKss, elicited by a test potential of +80 mV, by 40, 70, and 31%, respectively. Pretreatment of PA smooth muscle cells with 10 mM 4-aminopyridine (4-AP) prevented the subsequent inhibitory effect of clotrimazole on IKV. However, pretreatment of the cells with 1 mM tetraethylammonium negligibly altered the effects of miconazole on IKV and Em. In current-clamp (I = 0) measurements, clotrimazole depolarized PA myocytes by 9 and 11 mV during perfusion with Ca(2+)-containing and Ca(2+)-free bath solution, respectively. 1-ABT also caused a 9-mV depolarization in PA myocytes bathed in Ca(2+)-free solution. These effects are similar to those induced by hypoxia, reduced glutathione, and 4-AP. Clotrimazole also decreased IKV and depolarized mesenteric arterial myocytes. These data raise the possibility that the P-450 system, due to its influence on IKV and sensitivity to O2 tension and NADPH, may play a role in linking the regulation of pulmonary vascular tone to the alteration of cellular redox status through a common pathway of KV channel activity.

Role of methylation in placental major histocompatibility complex antigen expression and fetal loss

The purpose of this study was to determine the role of gene methylation on major histocompatibility complex (MHC) antigen expression in the rat placenta, specifically: 1) the constitutive suppression of labyrinthine class I genes and of all class II genes, 2) genomic imprinting of class I genes, and 3) the amount of fetal loss in relationship to gene methylation. Placentas from all four mating combinations, or a subset thereof, of the inbred DA and WF strains of rats were studied simultaneously through 1) molecular assessment of their levels of methylation at various stages of pregnancy and changes in methylation after treatment with 5-azacytidine and 2) immunohistochemical determination of their MHC class I and class II antigen expression. Treatment with 5-azacytidine caused demethylation of both class I and class II genes, the level depending upon the method of administration of the drug. Treatment with 5-azacytidine did not, however, alter the expression of either the class I or class II antigens. Hence, demethylation is not involved in the constitutive suppression of labyrinthine class I genes or that of all placental class II genes, and it is not involved in the genomic imprinting of placental class I genes. The effect of 5-azacytidine on fetal loss is due to its direct cellular effects and not to an immunological mechanism.

Deoxyglucose and reduced glutathione mimic effects of hypoxia on K+ and Ca2+ conductances in pulmonary artery cells

Hypoxia-induced pulmonary vasoconstriction (HPV) is triggered by a rise in cytosolic Ca2+ concentration ([Ca2+]i) that is partially controlled by voltage-gated Ca2+ channels. Hypoxia inhibits voltage-gated K+ (KV) channels in pulmonary artery (PA) myocytes. This depolarizes the cells, opens voltage-gated Ca2+ channels, thereby increases [Ca2+]i, and initiates HPV. In intact animals and isolated perfused lungs, metabolic inhibitors and reducing agents augment HPV. We compared the effects of hypoxia with the glycolysis inhibitor, 2-deoxy-D-glucose (2-DOG), and the reducing agent, reduced glutathione (GSH), on voltage-gated steady-state K+ currents (IK,ss) and membrane potential (Em) in cultured rat pulmonary and mesenteric arterial (MA) smooth muscle cells. Bath application of 10 mM 2-DOG (glucose-free) or 5-10 mM GSH reversibly reduced IK,ss by 25-35% in PA myocytes, with 5 mM ATP present in the pipette solution. Neither hypoxia nor 2-DOG significantly affected IK,ss in MA myocytes, but GSH did reduce IK,ss in these cells. Furthermore, hypoxia, 2-DOG, and GSH depolarized PA cells in the absence as well as in the presence of external Ca2+. Hypoxia, 2-DOG, and GSH also evoked action potentials on the top of the steady depolarization in 36-50% of PA myocytes but not in any MA myocytes; removal of external Ca2+ abolished the action potentials without affecting the steady depolarization. These effects were comparable to those produced by 4-aminopyridine (5-10 mM), a blocker of KV channels. This implies that the action potentials are attributable to Ca2+ influx through voltage-gated Ca2+ channels opened by the steady depolarization due to KV channel inhibition. In the presence of 2-DOG or GSH, hypoxia had no further effect on IK,ss or Em in PA cells; this implies that hypoxia, 2-DOG, and GSH all block the same K+ channels. The data suggest that 1) the hypoxia-induced decrease of IK,ss and the resultant depolarization in PA myocytes may be related to a local decrease of intracellular ATP level and/or a change in redox status of the membrane or cytosol and 2) extracellular Ca(2+)-dependent action potentials may be responsible for at least part of the increase in [Ca2+]i during HPV. Similarities between the effects of hypoxia, 2-DOG, and GSH on IK,ss and Em in PA myocytes, along with the dissimilar responses of PA and MA myocytes, suggest that a common mechanism may underlie the responses of PA cells to these treatments.

Nitrone spin-traps block calcium channels and induce pulmonary artery relaxation independent of free radicals

Free radicals react with nitrones to form stable nitroxides which can be identified by ESR spectroscopy. Unfortunately, little is known regarding the pharmacological properties of these compounds. In this study, three commonly used nitrones, 5,5-dimethylpyrroline-N-oxide (DMPO), alpha-phenyl-tert-butylnitrone (PBN), and alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone (POBN), were found to induce relaxation of preconstricted isolated rat pulmonary artery rings. Additional experiments with PBN indicated that vasorelaxation could not be attributed to production of endothelial derived factors, prostaglandins, or free radicals. Patch-clamp techniques revealed reversible calcium channel blockade with PBN at a concentration below that needed to detect free radicals. Calcium channel blockade probably accounts for the vasorelaxation observed in the isolated ring preparations described here, and should be considered when using nitrone spin-traps both in in vivo and clinical studies.

Hypoxia reduces potassium currents in cultured rat pulmonary but not mesenteric arterial myocytes

To explore possible mechanisms underlying hypoxia-induced pulmonary vasoconstriction, the effect of hypoxia on outward K+ current (Iout) was evaluated in primary cultured rat pulmonary (PA) and mesenteric (MA) arterial smooth muscle cells using the whole cell patch-clamp technique. When the cells were bathed in standard physiological salt solution and the patch pipettes contained Ca(2+)-free media with 10 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), virtually all of the Iout, including both the rapidly inactivating component (Irt) and the steady-state (noninactivating) component (Iss), was mediated by voltage-gated K+ channels. Reduction of O2 tension in the bath solution from 155 Torr to < 74 Torr with sodium dithionite reversibly inhibited both Irt and Iss in PA myocytes, but not in MA myocytes. The hypoxia-sensitive Iss was activated at about -50 mV; thus, some of the channels responsible for this current may be open at the resting membrane potential (-40 +/- 1 mV) of PA cells used in this study. Hypoxia also significantly depolarized PA cells bathed in PSS (1.8 mM Ca2+) from -40.7 +/- 1.3 to -24.0 +/- 2.4 mV, and PA cells bathed in Ca(2+)-free PSS (0.1 mM EGTA) from -38.4 +/- 1.3 to -26.1 +/- 3.9 mV. The hypoxia-induced inhibition of Iout in PA cells was accompanied by an apparent increase in inward Ca2+ current.(ABSTRACT TRUNCATED AT 250 WORDS)

Ionic currents in rat pulmonary and mesenteric arterial myocytes in primary culture and subculture

The electrophysiological properties of cultured single vascular smooth muscle (VSM) cells from rat pulmonary (PA) and mesenteric (MA) arteries were studied using the whole cell patch-clamp technique. Cells were studied at 3-7 days as primary cultures, or were replated after 10-20 days and subcultured for 2-5 days. In the standard physiological bath solution (containing 1.8 mM Ca2+), and with 125 mM K+ + 10 mM ethylene glycol-bis(beta-aminoethyl ether)- N,N,N',N'-tetraacetic acid (EGTA)-filled pipettes, both PA and MA primary cultured cells had high input resistances (mean = 2-3 G omega) and resting membrane potentials of about -40 mV. The cells were clamped at a holding potential of -70 mV. Depolarization to -20 mV or more evoked a transient inward current (Iin) that was eliminated in Ca(2+)-free bath solution; this indicates that Iin was carried by Ca2+. Iin was substantially smaller in subcultured cells from both PA and MA. Depolarization also activated three components of outward current (Iout) in primary cultured PA and MA cells: a rapidly inactivating transient component (Irt), a slowly inactivating transient component (Ist), and a steady-state (noninactivating) component (Iss). All three components of Iout were inhibited to varying degrees by 5 mM 4-aminopyridine and were eliminated by replacing intracellular K+ with Cs+, but were only minimally affected by removal of extracellular Ca2+. These results suggest that this Iout was carried by K+ and was voltage gated. Little external Ca(2+)-dependent Iout was observed under these conditions, but a substantial Ca(2+)-dependent component was seen when the EGTA concentration in the pipettes was reduced to 0.1 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of L-4-oxalysine on ultrastructures of liver cells in mice

Mice were given ig L-4-oxalysine (I-677) 10, 50, and 100 mg.kg-1.d-1 for 7 d. On d 8 the hepatocytes showed accumulation of lipid droplets followed by loss of matrices in cytoplasm. The total area of lipid droplets was far less than 25% of mean section of hepatocytes. The injury of mitochondria and RER was only found in the groups of medium and high dose. The lipidoses and regional topolysis of cytoplasm graduated away at same pace. After 4 wk the hepatocytes were restored to normal. Such finding suggests that the site of action of I-677 be at the cytoplasmic ground substance. The inhibition of protein synthesis causes a decrease in albumin carrier, that may be the main mechanism of steatosis of liver cells induced by I-677.

Contrasting effects of hypoxia on tension in rat pulmonary and mesenteric arteries

The effects of hypoxia on resting and K-stimulated tension were tested on small rings of rat pulmonary and mesenteric resistance arteries (SPA and SMA, respectively) and on the large branches of the main pulmonary artery (LPA). Reduction of PO2 from approximately 135 Torr to less than 40 Torr slowly increased SPA and LPA resting tension but did not affect SMA tension. The increases in SPA and LPA tension during hypoxia were reversible and were dependent on external Ca2+. Verapamil, 10(-6) M, inhibited the hypoxic pulmonary vasoconstriction by 53-78%. The hypoxia-contracted SPA and LPA were relaxed by 2-4 microM cromakalim; these relaxations were reversed by 2 microM glibenclamide. Hypoxia attenuated the K-stimulated tension (delta TK) in both SPA and SMA at all external K+ concentrations ([K+]o = 10-100 mM) without affecting the shapes of the respective [K+]o-tension curves. However, the SPA curve was located much farther to the left on the [K+]o axis than the SMA curve. [K+]o congruent to 13 mM evoked a half-maximal increase in SPA tension; maximal delta TK was observed at [K+]o greater than or equal to 30 mM. In contrast, [K+]o less than 20 mM induced a negligible increase in SMA tension, whereas 35-40 mM K+ activated about one-half of the increase in tension elicited by 100 mM K+. The LPA [K+]o-tension curve in normoxia was intermediate between the SMA and SPA curves, but hypoxia shifted the LPA curve to the left: delta TK was augmented at [K+]o less than 20 mM and attenuated at high [K+]o.(ABSTRACT TRUNCATED AT 250 WORDS)

[Influence of laurocapram on ultrastructures of mouse skin and sarcoma 180 membrane]

Laurocapram (Lau), 1-dodecyl-hexahydro-2 H-azepin-2-one, (azone) is a new percutaneous penetration enhancer. However, the mechanism of its action for absorption promoter of other agents is still unknown. In this paper the effect of Lau on ultrastructures of skin surface and tumor cell membrane were studies. Lau (2%) suspension was applied to abdominal skin of ICR/JCL, C 57 BL mice or one side of abdominal skin of nude mouse with drug and other side with the vehicle solvent once daily for 2-3 d. The skin was excised at 4 h after the final medication for examination under scanning electron microscope (SEM). The results showed the numerous small infolding lines which divided the skin surface into small areas with vesiculation and peeled the epidermal surface to form a few minor holes. The cuticles of the hair shaft dropped off and became thinner. Numerous desquamated cells around the orifice of the hair were fractured, detached and widened. Sarcoma 180 cells were incubated with Lau 25 micrograms/ml at 37 degrees C for 4 h. The microvilli of some cells dropped off and the size of villi became thinner and shorter. The top of some villi of the cells appeared occasionally thick to make the profile as a bat. The surface of numerous naked cells became rugged and rough and showed many black minor holes in the area of denuded cell membrane or dropped microvilli. More than 100 holes in the exposed surface of the naked cell were seen. It seemed that the Lau drilled holes on the biomembrane and enlarged the orifice of hair follicles and thus enhanced the transdermal absorption.