Preclinical development of orally available sphingosine kinase inhibitors

e14615

Background: Sphingolipid-metabolizing enzymes control the dynamic balance of important bioactive lipids, including apoptotic ceramide and proliferative sphingosine 1-phosphate (S1P). Several growth factors and inflammatory cytokines promote the cleavage of sphingomyelin and ceramide leading to rapid elevation of S1P levels through the action of sphingosine kinases (SKs). SK1 is oncogenic and is markedly overexpressed in a variety of human cancers, making this enzyme a potential molecular target for cancer therapy. Methods: SK inhibitors were synthesized and evaluated in a variety of cellular and in vivo models. Antitumor activity was assessed in an allogeneic model utilizing murine JC mammary adenocarcinoma cells growing in Balb/c mice, and a xenograft model of human Bxpc pancreatic adenocarcinoma cells growing in scid-mice. Results: The lead SK inhibitors, called ABC294640 and ABC294735, inhibit SK1 and SK2 at low micromolar concentrations, and are nontoxic to rodents at acute doses up to at least 1000 mg/kg (po). ABC294640 is orally-available, and has excellent pharmacokinetics, with serum levels exceeding the effective SK inhibitory concentration for at least 8 hours. Acute- and chronic- toxicology studies indicate that ABC294640 induces a transient minor decrease in the hemotocrit of rats and mice receiving 100 and 250 mg/kg/day; however, this normalizes by 28 days of treatment. No other changes in hematology parameters, or gross or microscopic tissue pathology result from treatment with ABC294640. Oral administration of ABC294640 to mice bearing JC adenocarcinomas results in dose-dependent antitumor activity associated with depletion of S1P levels in the tumors and progressive tumor cell apoptosis. ABC294735 is also orally-active in both JC and Bxpc tumor models, and demonstrates synergistic antitumor activity when combined with cisplatin or gemcitabine. Conclusions: These newly developed SK inhibitors provide orally-available drug candidates for the treatment of pancreatic cancer and other diseases. IND-enabling CMC and toxicology work is currently underway, and an SK inhibitor is expected to enter clinical trials in early 2010.

[Table: see text]

[Safety analysis of dust mite allergen for diagnosis and immunotherapy of asthma and rhinitis]

AIM

To make a retrieval investigation of safety in using Dermatophagoides farinae extract in diagnosis and immunotherapy with patients of asthma and rhinitis.

METHODS

A questionnaire evaluation of the safety use of D. farinae extract (SMU-Df) during diagnosis and immunotherapy of patients from 1974 to 1995 was carried out.

RESULTS

A total of 8,46,342 injections were statistically analysed, among whom 142 systemic adverse reactions occurred involving urticaria 0.82@10000, severe attack of asthma 0.77@10000, anaphylactic shock 0.07@10000 (CL = 1.4-12.0/million), and angioedma 0.02@10000. The time of onset of systemic reactions of immediate type was < 30 min in 32 cases-times, and 1 h and 2 h in 6 cases-times; the time to onset of late response type was 3 h-48 h in 23 cases-times with highest incidence of severe asthmatic attacks. The systemic reactions occurred in 18 subjects during skin test, in 96 cases-times during increasing dose phase, and in 14 cases-times during. Among them 6 cases were of anaphylactic shock, and none of it after emergency treatment. The major cause of manifestation of systemic reactions for 41 cases after immunotherapy with SMU-Df extract was due to over dosage errors.

CONCLUSION

The application of SMU-Df extract in skin test and immunotherapy of asthma and rhinitis sensitive to mite for the past 22 years in this country indicated that the efficacy and safety have been high.

Dietary curcumin supplementation counteracts reduction in levels of molecules involved in energy homeostasis after brain trauma

Traumatic brain injury (TBI) is followed by an energy crisis that compromises the capacity of the brain to cope with challenges, and often reduces cognitive ability. New research indicates that events that regulate energy homeostasis crucially impact synaptic function and this can compromise the capacity of the brain to respond to challenges during the acute and chronic phases of TBI. The goal of the present study is to determine the influence of the phenolic yellow curry pigment curcumin on molecular systems involved with the monitoring, balance, and transduction of cellular energy, in the hippocampus of animals exposed to mild fluid percussion injury (FPI). Young adult rats were exposed to a regular diet (RD) without or with 500 ppm curcumin (Cur) for four weeks, before an FPI was performed. The rats were assigned to four groups: RD/Sham, Cur/Sham, RD/FPI, and Cur/FPI. We found that FPI decreased the levels of AMP-activated protein kinase (AMPK), ubiquitous mitochondrial creatine kinase (uMtCK) and cytochrome c oxidase II (COX-II) in RD/FPI rats as compared to the RD/sham rats. The curcumin diet counteracted the effects of FPI and elevated the levels of AMPK, uMtCK, COX-II in Cur/FPI rats as compared to RD/sham rats. In addition, in the Cur/sham rats, AMPK and uMtCK increased compared to the RD/sham. Results show the potential of curcumin to regulate molecules involved in energy homeostasis following TBI. These studies may foster a new line of therapeutic treatments for TBI patients by endogenous upregulation of molecules important for functional recovery.

Efficient generation of multi-copy strains for optimizing secretory expression of porcine insulin precursor in yeast Pichia pastoris

AIMS

This study attempted to fully explore the expression potentials of Pichia pastoris for producing porcine insulin precursor (PIP) through PIP copy number optimization.

METHODS AND RESULTS

Multi-copy strains were screened employing a highly efficient improved in vivo method and their copy numbers were quantified by real-time qPCR. A range of Mut(+)P. pastoris strains harbouring 0, 1, 3, 6, 12, 18, 29, 52 copies of PIP were obtained. After 96 h methanol induction, a bell-shaped correlation curve was observed between gene dosage and protein yield, and the maximum PIP expression level of 181 mg l(-1) was achieved by a 12-copy strain. Specific growth rate and methanol utilization capacity were found to decrease remarkably for high copy strains (>12 copies). Transcriptional analysis of KAR2 suggested higher copy strains were suffering more from ER stress.

CONCLUSIONS

A copy number around 12 is optimal for secretory expression of PIP in P. pastoris. Excess PIP gene dosage (>12 copies) significantly impaired the growth of P. pastoris hosts.

SIGNIFICANCE AND IMPACT OF THE STUDY

The methods developed and the discoveries made by this systematical investigation will be helpful to the application and understanding of Pichia pastoris expression system for heterologous overexpression.

Quitting cigarettes completely or switching to smokeless tobacco: do US data replicate the Swedish results?

BACKGROUND

Swedish male smokers are more likely than female smokers to switch to smokeless tobacco (snus) and males' smoking cessation rate is higher than that of females. These results have fuelled international debate over promoting smokeless tobacco for harm reduction. This study examines whether similar results emerge in the United States, one of few other western countries where smokeless tobacco has long been widely available.

METHODS

US DATA SOURCE: national sample in Tobacco Use Supplement to Current Population Survey, 2002, with 1-year follow-up in 2003. Analyses included adult self-respondents in this longitudinal sample (n = 15,056). Population-weighted rates of quitting smoking and switching to smokeless tobacco were computed for the 1-year period.

RESULTS

Among US men, few current smokers switched to smokeless tobacco (0.3% in 12 months). Few former smokers turned to smokeless tobacco (1.7%). Switching between cigarettes and smokeless tobacco, infrequent among current tobacco users (<4%), was more often from smokeless to smoking. Men quit smokeless tobacco at three times the rate of quitting cigarettes (38.8% vs 11.6%, p<0.001). Overall, US men have no advantage over women in quitting smoking (11.7% vs 12.4%, p = 0.65), even though men are far likelier to use smokeless tobacco.

CONCLUSION

The Swedish results are not replicated in the United States. Both male and female US smokers appear to have higher quit rates for smoking than have their Swedish counterparts, despite greater use of smokeless tobacco in Sweden. Promoting smokeless tobacco for harm reduction in countries with ongoing tobacco control programmes may not result in any positive population effect on smoking cessation.

A novel blocking monoclonal antibody recognizing a distinct epitope of human CD40 molecule

CD40, a member of the tumor necrosis factor receptor superfamily, is an important costimulatory molecule during the immune response. Here, we report a blocking mouse antihuman CD40 monoclonal antibody, mAb 3G3, of which the specificity was verified by flow cytometry and Western blot. It was shown by competition test that 3G3 bound to a different site (epitope) of CD40 from the reported CD40 mAbs, including clone mAb89, 3B2, and 5C11. It was also found that mAb 3G3 could inhibit homotypic aggregation of Daudi cells induced by the agonistic anti-CD40 mAb 5C11. Furthermore, mAb 3G3 effectively inhibited the proliferation of peripheral blood mononuclear cells in mixed lymphocyte reaction assay. Finally, a sensitive and specific soluble CD40 (sCD40) ELISA kit was established by matching mAb 3G3 with 5C11, and it was found that the levels of sCD40 in sera from patients with immune disorders such as hyperthyroidism, chronic nephritis, and rheumatoid arthritis were obviously higher than those from normal individuals. Thus, this blocking anti-CD40 mAb provides a novel tool for the study of CD40.

Characterization and application of two novel monoclonal antibodies against CD40L: epitope and functional studies on cell membrane CD40L and studies on the origin of soluble serum CD40L

CD40 ligand, a 33-kDa cell membrane molecule, a member of the tumor necrosis factor superfamily, is an important costimulatory molecule during immune response. Here, we report on two functional mouse anti-human CD40L monoclonal antibodies 1B1 and 4F1 characterized by flow cytometry, Western blotting, and competition assay. The antibodies bound to distinct CD40L epitopes and therefore resulted in different bioactivity. Both antibodies could induce CD4+ T-cell alloantigenic hyporesponsiveness ex vivo. The antibodies were matched to develop a two-site enzyme-linked immunosorbent assay (ELISA) for soluble CD40L (sCD40L). Using this ELISA assay, we found major differences between plasma and serum sCD40L levels. Because the count of platelet sharply decreased in aplastic anemia (AA) and idiopathic thrombocytopenic purpura (ITP), we further analyzed the sCD40L concentration in the plasma of AA and ITP patients. The results showed that the sCD40L in serum was much lower than that of healthy subjects. These data demonstrate that platelets seem to be a major contributor to sCD40L, though not the only source of sCD40L in serum.

Efficient propagation of TM polarized light in photonic crystal components exhibiting band gaps for TE polarized light

We have investigated the properties of TM polarized light in planar photonic crystal waveguide structures, which exhibit photonic band gaps for TE polarized light. Straight and bent photonic crystal waveguides and couplers have been fabricated in silicon-on-insulator material and modelled using a 3D finite-difference-time-domain method. The simulated spectra are in excellent agreement with the experimental results, which show a propagation loss as low as 2.5+/-4 dB/mm around 1525 nm and bend losses at 2.9+/-0.2 dB for TM polarized light. We demonstrate a high coupling for TM polarized light in a simple photonic crystal coupler with a size of ~ 20 m x 20 m. These promising features may open for the realization of ultra-compact photonic crystal components, which are easily integrated in optical communication networks.

Relationship between endogenous estrogen concentrations and serum cholesteryl ester transfer protein concentrations in Chinese women

BACKGROUND

CETP plays an important role in HDL metabolism and in the reverse cholesterol transport pathway.

METHODS

The relationship between the changes of endogenous estrogen and the concentration of cholesteryl ester transfer protein (CETP) in the serum of Chinese women was investigated. Serum concentrations of estradiol (E(2)), follicle-stimulating hormone (FSH), CETP and lipid profile were determined in 196 Chinese women (52 premenopausal with ages ranging from 18 to 40 years, 57 perimenopausal from 41 to 60 years, and 87 postmenopausal from 61 to 81 years).

RESULTS

Serum CETP concentration was significantly lower in postmenopausal women compared with those in perimenopausal and premenopausal women (1.39+/-1.06, 2.36+/-1.50 and 2.31+/-1.25 mg/l, respectively, P<0.0001). Even in the women around the menopausal, CETP concentration in postmenopause was significantly lower than that in premenopause (1.93+/-1.33 vs. 3.42+/-1.35 mg/l, P<0.01). In addition, CETP concentration had a highly positive correlation with serum concentration of E(2) (r=0.243, P<0.001), while negative correlation of CETP concentration with serum concentration of FSH was found (r=-0.273, P<0.001).

CONCLUSIONS

Estrogen may affect the concentration of CETP.

Inhibitory effects of rosa roxburghii tratt juice on in vitro oxidative modification of low density lipoprotein and on the macrophage growth and cellular cholesteryl ester accumulation induced by oxidized low density lipoprotein

BACKGROUND

Rosa roxburghii tratt juice (RRTJ) administration has been shown to significantly ameliorate atherosclerotic diseases in cholesterol-fed animals. However, the mechanism for the antiatherogenic effect of RRTJ is not clear.

METHODS

We investigated the effects of RRTJ on in vitro oxidative modification of LDL and on LDL-induced macrophage growth and cellular cholesteryl ester (CE) accumulation. The effects of RRTJ on LDL oxidative modification were assessed by relative electrophoretic migration, thiobarbituric acid-reactive substance (TBARS) content, and the formation of conjugated dienes. The inhibition of RRTJ on oxidized LDL (Ox-LDL)-induced murine peritoneal macrophage growth was evaluated by a cell-counting assay and an MTT assay. The effect of RRTJ on Ox-LDL-induced cellular CE accumulation was examined after macrophages were incubated with Ox-LDL in the presence of RRTJ. To clarify the mechanism of the inhibitory effect of RRTJ on Ox-LDL-induced CE accumulation in macrophages, its capacity for cholesterol efflux from macrophage-derived foam cells were examined.

RESULTS

We showed that RRTJ significantly reduced LDL oxidative susceptibility. In addition, RRTJ effectively suppressed Ox-LDL-induced macrophage growth and especially Ox-LDL-induced CE accumulation in murine peritoneal macrophages by promoting cellular cholesterol efflux.

CONCLUSION

These results indicated that RRTJ exerted its antiatherogenic effects largely due to its ability to inhibit the oxidative modification of LDL and to suppress the formation of foam cells.

[Studies on characteristics of kinetics and metabolic shift of genetically engineered yeast Pichia pastoris in high-density chemostat cultivation]

Kinetics and metabolic shift of DNA recombinant yeast Pichia pastoris was studied in high-density chemostat cultivation in which the glycerol was used as a limited substrate. The experimental results showed that (1) cell optical density (OD600) of Pichia pastoris was linear with its dry cell weight (DCW) and wet cell weight (WCW), and reached 100 OD600 = 128.3 g WCW/L or 100 OD600 = 22.9 g DCW/L; (2) The relationship of specific growth rate (mu) and residual concentration of glycerol is accorded with Monod Equation, to obtain mu = mumax S/(Ks + S), where mumax = 0.366 h-1, Ks = 0.1823 g/L. The maximum cell yield of glycerol substrate YG = 0.54 g/g, growth maintaining coefficient m = 0.0069 g/(g.h), The cell yield of oxygen YX/O2 = 30.96 g/moL, and the optimum theoretical dilution rate Dm = 0.341 h-1 by parameter inference; (3) With specific growth rate (mu) increasing, glycerol metablic flux shifts linearly from glycogenesis and hexosephosphate pathways to glycolysis and tricarboxylic acid cycle pathways on basis of variations of consumption rate of NH3.H2O and respiratory quotient value.

The development of iodine based impinger solutions for the efficient capture of Hg0 using direct injection nebulization-inductively coupled plasma mass spectrometry analysis

Inductively coupled plasma mass spectrometry (ICP/MS) with direct injection nebulization (DIN) was used to evaluate novel impinger solution compositions capable of capturing elemental mercury (Hg0) in EPA Method 5 type sampling. An iodine based impinger solution proved to be very efficient for Hg0 capture and was amenable to direct analysis by DIN-ICP/MS. Hg0 capture efficiency using aqueous iodine (I3-) was comparable to Hg0 capture using acidified potassium permanganate impinger solutions which were analyzed by cold vapor atomic absorption spectrometry (CVAAS), with greater than 98% capture of Hg0 in the first oxidizing impinger. Using DIN-ICP/MS, it was demonstrated for the first time that iodine can be generated just prior to impinger sampling for efficiently oxidizing Hg0 and retaining it in solution as HgI4(2-). Due to the increased interest in Hg speciation from combustion sources and the potential for using DIN-ICP/MS for multiple metals analyses, an impinger sampling train for gaseous Hg speciation and multiple metals analyses using DIN-ICP/MS analyses is presented. The unique feature of such a sampling train is that each impinger solution in the series is amenable to direct analysis by DIN-ICP/MS. A bituminous coal was combusted in a bench scale coal system, and gaseous Hg species (oxidized and elemental) were determined using the proposed impinger train. The DIN-ICP/MS instrumental detection limit was 0.003 ppb, and MDLs ranged from 0.007 to 0.116 microg/L (ppb) in a variety of impinger solutions used for Hg capture.

A genetic investigation of E2A function in lymphocyte development

Lymphocytes are derived from hematopoietic stem cells (HSC) following a series of regulated differentiation events. Multipotent HSCs become committed to the B cell lineage in bone marrow and the T cell lineage in the thymus after receiving appropriate signals from the corresponding microenvironment. These committed lymphoid cells must then undergo V(D)J recombination at the immunoglobulin gene or T cell receptor gene locus resulting in clonal production of functional B or T lymphocytes, respectively. Lymphocyte commitment and differentiation are accompanied by programmed gene expression or repression events which are driven by lineage and stage specific transcription factors. The basic-helix-loop-helix (bHLH) transcription factors encoded by the E2A gene are involved in several differentiation events during B and T cell development, including lineage commitment, initiation of V(D)J recombination, and antigen receptor mediated proliferation and differentiation. Several recent reviews have provided a comprehensive discussion of biochemical, cellular, and genetic research on E2A function in lymphocyte development (1,2). Here, we only discuss some of the genetic approaches our laboratory (except where it is noted) has undertaken to investigate the molecular pathways mediated by E2A transcription factors in lymphocyte development.

[Sulfa-drug wastewater treatment with anaerobic/aerobic process]

Sulfa drug wastewater was treated with anaerobic/aerobic process. The removal ratios of TOC reached about 50% in anaerobic phase and about 70% in aerobic phase respectively, while volume loading rate of TOC was about 1.2 kg/(m3.d) in anaerobic phase and about 0.6 kg/(m3.d) in aerobic phase. Removal of TOC in anaerobic phase was attributed to the reduction of sulfate.

[Clinical analysis of tubulointerstitial lesions in IgA nephropathy]

OBJECTIVE

To analyze the characteristics of tubulointerstitial lesions (TIL) in IgA nephropathy (IgAN).

METHODS

The pathologic and clinical materials of 609 IgAN patients were analyzed.

RESULTS

(1) Prevalence characteristics of TIL: Among all the patients, these with mild TIL accounted for 47.1%, moderate TIL 21.7%, severe TIL was about 16.6% and these without TIL 14.6%. (2) Relationship between TIL and the clinical findings: With increase of the severity of TIL, hypertension became worse and the level of proteinuria increased gradually. On the contrary, serum albumin decreased and renal function degraded. (3) Relationship between TIL and the pathologic findings: With increase of the severity of TIL, the scores of vascular lesion, total glomerular lesion, hypercellularity and glomerulosclerosis increased gradually. Moreover, when the glomerular lesion and vascular lesion became worse, the severity of TIL also increased. The relationship with the crescents was different, the score of the presence of crescents was highest when TIL was moderate in severity; it would not increase when TIL was severe.

CONCLUSION

With the increase of the severity of TIL, the condition of IgAN patients became worse. TIL may be one of the key factors for the prognosis of IgAN. TIL is closely related to the severity of glomerular and vascular lesions, and these lesions may further lead to the development of TIL.

Serum cholesteryl ester transfer protein concentrations in healthy Chinese subjects and cardio-cerebrovascular disease patients

Serum cholesteryl ester transfer protein (CETP) concentration was measured in 1128 healthy Chinese subjects using a "sandwich" enzyme immunoassay and was 1.84 +/- 1.55 mg/l (mean +/- S.D.). The frequency distribution of CETP in healthy subjects was markedly skewed towards low concentrations. The CETP concentration in females was significantly higher than that in males (2.40 +/- 1.65 mg/l vs. 1.49 +/- 1.37 mg/l, P < 0.001). There was a weak inverse correlation between the CETP concentration and age (r = -0.19, P < 0.001). The CETP concentrations were significantly higher in 117 myocardial infarction (MI) survivors and 110 stroke patients than that in 335 healthy, age-matched males (1.98 +/- 1.68 173 +/- 1.45, and 1.40 +/- 1.37 mg/l respectively, P < 0.01), while no relation was found between CETP concentration and lipids concentration in MI, stroke and healthy group.

[Relationship of abnormal umbilical artery flow velocity waveforms and placental pathology]

OBJECTIVE

To investigate the relationship of abnormal umbilical artery (UmA) flow velocity waveforms (FVWS) with placental weight, volume and all classes of villi and vessels.

METHODS

Ten IUGR with abnormal umbilical artery(AA) were set as pathological group. Ten normal weight births with abnormal UmA FVWS(AN), 10 IUGR with normal UmA FVWS (NA), 10 normal weight births with normal UmA FVWS (NN) were selected as controls. Anti-alpha-SMA antibody was used to examine placental stem vessels and stem villi. The placental weight, volume, numbers of all classes of villi and vessels were compared.

RESULTS

(1) Placental weight and volume in pathological group reduced significantly, while compared with AN (P < 0.01, P < 0.05, respectively), NA (P < 0.01, P < 0.001, respectively), and NN (all the P values < 0.001). (2) When the pathological group was compared with other 3 control groups with respect to the numbers of all classes of villi and vessels in placenta, the number of stem vessels reduced significantly (P < 0.05, P < 0.01, P < 0.001 respectively). The number of stem villi reduced significantly, compared with NA and NN (P < 0.01, P < 0.001, respectively). The number of stem villi did not change when compared with AN (P > 0.05).

CONCLUSION

Abnormal UmA FVWS is related with placental weight, volume, all classes of villi and vessels. The reduction of villous and vascular number may be due to arrest of placental angiogenesis but not selective obliteration of vessels.

[Adsorption of anthraquinone dyes by biosorbent GX2]

The GX2 growing mycelium shows excellent adsorptive capacity on the four kinds of anthraquinone dyes, however, due to the difference of molecular structure of dyes, the adsorption rates are different. Although the dyes show inhibiting effect on the growth of GX2, when the concentration of reactive brilliant blue KN-R is 250 and 400 mg/L, the adsorption rate of dye by the GX2 growing mycelium reaches 100% and 91.4%, respectively. With the increase of salinity (NaCl), the dry weight of GX2 mycelium increases; the diameter of granular mycelium decreases and its adsorption surface area increases accordingly, the salinity shows evident enhancement on the adsorption of reactive brilliant blue KN-R by GX2 growing mycelium in the range of 0%-2% salinity. The adsorption process is influenced by the concentration of carbon source as well, reactive brilliant blue KN-R with the concentration of 120 mg/L can be completely adsorbed only when the concentration of glucose is more than 2.5 g/L. The GX2 growing mycelium has better adsorptive capacity than resting living mycelium and dead mycelium.

Up-regulation of Na,K-ATPase beta 1 transcription by hyperoxia is mediated by SP1/SP3 binding

The sodium pump, Na,K-ATPase, is an important protein for maintaining intracellular ion concentration, cellular volume, and ion transport and is regulated both transcriptionally and post-transcriptionally. We previously demonstrated that hyperoxia increased Na,K-ATPase beta(1) gene expression in Madin-Darby canine kidney (MDCK) cells. In this study, we identify a DNA element necessary for up-regulation of the Na,K-ATPase beta(1) transcription by hyperoxia and evaluate the nuclear proteins responsible for this up-regulation. Transient transfection experiments in MDCK cells using sequential 5'-deletions of the rat Na,K-ATPase beta(1) promoter-luciferase fusion gene demonstrated promoter activation by hyperoxia between -102 and +151. The hyperoxia response was localized to a 7-base pair region between -62 and -55, which contained a GC-rich region consistent with a consensus sequence for the SP1 family, that was sufficient for up-regulation by hyperoxia. This GC element exhibited both basal and hyperoxia-induced promoter activity and bound both transcription factors SP1 and SP3 in electrophoretic mobility shift assays. In addition, electrophoretic mobility shift assays demonstrated increased binding of SP1/SP3 in cells exposed to hyperoxia while mutation of this element eliminated protein binding. Other GC sites within the proximal promoter also demonstrated up-regulation of transcription by hyperoxia, however, the site at -55 had higher affinity for SP proteins.

[The studies on the molecular mechanism of rifampin-resistant Mycobacterium tuberculosis]

OBJECTIVE

To evaluate the molecular mechanism of rifampin (RFP)-resistance of M. tuberculosis, and to provide evidence of molecular genetics for basic and clinical research of tuberculosis.

METHODS

rpoB gene mutation of M. tuberculosis was detected with PCR-SSCP from 262 clinical isolates, including 74 drug sensitive strains, and 188 RFP-resistant only or multiple drug-resistant strains of M. tuberculosis, collecting from Henan, Hebei and Anhui province, Beijing and Shanghai cities. Plasmids were extracted from 76 clinical isolates of M. tuberculosis with alkaline bacteriolytic methods.

RESULTS

Mean mutation rate of rpoB gene was 92% in the RFP-resistant clinical isolates of M. tuberculosis. Respectively, the mutation rate was 90.0% in Henan province, 94% in Hebei province, 91% in Anhui province, 91% in Beijing city and 92% in Shanghai city. There was no significant difference between results from the provinces and the cities (chi 2 = 0.42, P > 0.05). However, mutation of rpoB gene was not detected in 74 sensitive clinical isolates of M. tuberculosis. Moreover, in 76 clinical isolates of M. tuberculosis the plasmids were not found, including 29 sensitive strains, 33 RFP-resistant only or multiple drug-resistant strains and 14 RFP, isoniazid, streptomycin and ethambutol-resistant clinical isolates.

CONCLUSIONS

This study confirmed the strong correlation between the RFP-resistance and the mutation of the rpoB gene, which might be a major molecular mechanism of RFP-resistance in M. tuberculosis. No evidence shows that M. tuberculosis has the plasmid, which mediates RFP resistance to M. tuberculosis.