Biomedical subjects

Z Gao

Publications and source records attributed to Z Gao.

At least 73 records · Page 4Linked to original sources

PubMed2000

[Changes of plasma levels of type C natriuretic peptide in patients with pregnancy induced hypertension].

OBJECTIVE: To investigate the changes and clinical significance of plasma type C natriuretic peptide (CNP) concentration in patients with pregnancy induced hypertension (PIH). METHODS: Plasma CNP levels were detected by radioimmunoassay in 89 patients with PIH, 193 normal pregnant women and 46 normal non-pregnant women. Outcomes were statistically analyzed by one-way analysis of variance and Student-Nawman-Kenls (SNK) test. RESULTS: The plasma CNP levels in patients with PIH [(30.51 +/- 33.61) ng/L] were significantly higher than those of normal non-pregnant women and normal pregnancies [(17.15 +/- 3.82) ng/L, (19.43 +/- 5.13) ng/L, respectively; F = 13.61, P < 0.01]. There was significant difference among plasma CNP levels from patients with mild, moderate, and severe PIH (P < 0.0001). CONCLUSIONS: The changes of plasma CNP levels are believed to be the reflection of patients in progression of PIH and can be used as a biochemical marker for judging the progression and guiding the therapy of PIH.

Adult↗

PubMed2000

[Hyperpolarized cardiac arrest with ATP-sensitive potassium channel opener on myocardial protection during CPB].

OBJECTIVE: To investigate the myocardial protective effects of pinacidil-induced hyperpolarized arrest and compare them with those induced with depolarized hyperkalemic arrest. METHODS: 18 dogs were equally divided into three groups. In the hypothermic hyperpolarization group (LH group), after aortic cross-clamping, a single dose of 4 degrees C pinacidil containing St. Thomas cardioplegic was infused through the aortic root. Temperature during CPB was kept between 26 - 28 degrees C and warmed to 37 degrees C before aortic declamping. Global ischemia lasted 60 min and then reperfusion started for 30 min. In the normothermic hyperpolarized group (WH group), the same procedure was set as in the LH group, except maintaining temperature of 35 - 37 degrees C for CPB and pinacidil solution. In the control group (group C), no pinacidil in St. Thomas solution was the only difference to the other 2 groups. Cardiac arrest and its recovery, the ultrastructure of the myocardium and hemodynamic during ischemia and after reperfusion were observed in the 3 groups. RESULTS: (1) The percentages of normal mitochondria and glycogen were not changed significantly during ischemia and after reperfusion in the LH group, but declined markedly in the group C at ischemic 30, 60 min, and reperfusion for 20 min (P < 0.01). In the WH group, they were lower than those of the group LH, but higher than those of the group C before ischemia. (2) The recoveries of CO, SV, CI, LVSW, RVSW, MAP in the LH group were significantly better than those in the other two groups after reperfusion for 15 minutes and 30 minutes (P < 0.05 or 0.01). However, they were much better in the WH group than in the group C (P < 0.05 or 0.01). (3) The time from cardioplegic infusion to cardiac arrest was shorter in the group C and the group LH than in the group WH. CONCLUSIONS: Myocardial protection for global ischemia during CPB could be well achieved with hyperpolarized cardiac arrest induced by ATP-sensitive potassium channel opener, pinacidil, especially in the hypothermic state. The protection is weaker in normothermia but is still stronger than that with traditional depolarized arrest.

Adenosine Triphosphate↗

PubMed2000

[A study on the association of telomere length with the experimental carcinogenesis of oral cavity].

OBJECTIVE: The life cycle of cell can be effected by the length of telomere. Loss of telomeric DNA during cell proliferation may play a role in chromosome instability, cellular apoptosis and cancer. The purpose of the study is to measure the dynamic changes of telomere length in experimental oral cavity cancer during golden hamster cheek pouch carcinogenesis induced by DMBA. METHODS: First, 52 golden hamsters were divided into 2 groups. Four of them were not done any treatment and were killed after 3 days. The others were covered with DMBA on the surface of cheek pouch on one side in order to induce carcinogenesis, the other side of cheek pouch was treated as the control. Then, the 48 golden hamsters were divided into 4 groups and were killed in 7, 10, 14, 20 weeks. Light microscope was used to observe the pathologic changes. Southern hybridization was used to analysis the dynamic development of the length of telomeric repeat. In different periods, the reduction rate of telomere length was calculated. RESULTS: 1. The cheek pouch mucosa uncovered with DMBA had no abnormal pathologic changes, while that covered with DMBA was observed pathologic changes of different degrees. 4 cases of hyperplasia lesions and 8 cases of dysplasia lesions were observed in the 7-week group, 7 cases of dysplasia lesions and 5 cases of mucosa carcinoma in situ in the 10-week group, 5 cases of mucosa carcinoma in situ, 4 cases of squamous cell carcinomas and 3 cases of death in the 14-week group, and 7 cases of squamous cell carcinomas and 5 cases of death in the 20-week group. 2. The telomere length of the normal mucosa was reduced with the hamsters age increasing, but the telomere length was significantly shorter than that of the normal control during the mucosa carcinogenesis of cheek pouch. The average shortened length was about 0.225 kb (the normal mucosa was 0.17 kb). 3. The highest reduction rate (0.3985) was in a later premalignant period. CONCLUSION: Age is one of the factors that can short telomere length. However, the speed that telomere length is shorted is faster than ever while telomere is abnormal. There is an obvious relationship between the abnormal degree of telomere length and the malignant degree of carcinoma. So the abnormal shorting of telomere length is an early molecular evidence of the oral carcinogenesis.

Animals↗

PubMed2000

[Identification of telomerase activity in the experimental carcinogenesis of oral cavity].

OBJECTIVE: Telomerase is a ribonucleoprotein enzyme which synthesizes telomere DNA repeat sequences and maintain stably telomere length. The activity of telomerase may be necessary for the growth of immortalized cells overcoming cellular senescence. The researches have shown that telomerase activities are associated with most cancers. The purpose of the study is to detect the development of telomerase activity during golden hamster cheek pouch carcinogenesis induced by DMBA. METHODS: First, 52 golden hamsters were divided into 2 groups. Four of them were not done any special treatment and were killed after 3 days. The others were covered with DMBA on the surface of cheek pouch on one side in order to induce carcinogenesis, the other side of cheek pouch was treated as the control. Then, the 48 golden hamsters were divided into 4 groups and were killed in 7, 10, 14 and 20 weeks. The telomeric repeat amplification protocol (TRAP) based on PCR and ELISA was used to analysis the activity of telomerase. RESULTS: 1. The expression of telomerase activity existed in normal cheek pouch mucosa of golden hamsters, which meant that telomerase played an important role on controlling cell proliferation. 2. The level of telomerase activity gradually increased while hyperplasia and dysplasia was observed in the cheek pouch mucosa covered with DMBA. It reached its top at a later premalignant period and gradually decreased after that. 3. There was negative correlation between the degree the telomere length was shortened and the activity of telomerase (r = -0.9654), and there was positive correlation between the reduced rate of telomere length and the activity of telomerase (r = 0.9471). CONCLUSION: The activity of telomerase is one of important factors that can effect the stability of telomere length and plays a crucial role in the progression of oral cancer. So the activity of telomerase is an early molecular marker of carcinogenesis.

Animals↗

PubMed2000

[Application of RAPD in the taxonomy of the genus Fritillaria].

OBJECTIVE: To provide the molecular data for the right application of the Chinese medicine "Beimu". METHOD: Using the technology of RAPD, we studied the relationship among 12 samples of Beimu. RESULT: The total genomic DNA of all the samples are about 21 Kb in size. Among 20 primers used, the five primers can reatedly generate a certain specified amplified band type, 27 bands were recored from all amplified products and 25 polymorphic fragments were found in it. The size of amplified fragments is between 450 bp and 1904 bp. CONCLUSION: The similarity within species is higher than those between species. The relationship of Fritillaria anhuiensis and F. puqiensis is the farest, while F. thunbergii and F. puqiensis is the closest.

DNA Primers↗

PubMed2000

[The use of muscle autograft or nerve allograft denatured by microwave for repair of gaps in rat facial nerve].

OBJECTIVE: Attempt to enhance recovery of rat facial nerve through different grafts. METHODS: Rats facial nerve mandible branch gap was repaired using different grafts, either muscle autograft or sural nerve allograft denatured by microwave. Axonal regeneration was studied in 10th week after insertion of the denatured muscle autografts or sural nerve allografts and compared with results found in autologous sural nerve grafts used as controls. Axonal regeneration, Schwann cell behavior and efficacy of nerve and muscle were quantified using CB-HRP retrograde trace, HE staining, Flamming staining and electromyography. RESULTS: Denatured nerve allografts and muscle autografts supported the higher rates and volumes of axonal regeneration. Nerve allografts had the higher degree of myelin sheath developing. CONCLUSION: Nerve autograft and muscle autograft denatured by microwave are convenient, source sufficient, higher efficient grafts for repairing facial nerve gap and have potential clinical use.

Animals↗

PubMed2000

[Effect of organic tin on the morphology and mechanical properties during polyurethane-urea curing process].

The mechanical properties and morphology of crosslined PUU in bulk quasi-prepolymer process was studied by in situ FTIR. From the quantitative change of carbonyl FTIR spectra, the development of morphology between noncatalyzed and catalyzed polymerization process was discussed in detail. The effect of organic tin concentration on the mechanical properties was investigated. It showed that urea carbonyl splitted many small weak bands at different sites with increasing of organic tin concentration, and the catalyst played an important role in controlling the morphology and mechanical properties. It also showed that the mechanical properties reached extreme value when the rate constant of -NCO/-OH reaction equate the rate constant of -NCO/-OH reaction.

Catalysis↗

PubMed1999

Complement inhibition with an anti-C5 monoclonal antibody prevents hyperacute rejection in a xenograft heart transplantation model.

BACKGROUND: The present study was undertaken to determine whether anti-complement 5 (C5) monoclonal antibodies (mAb) prevent hyperacute rejection (HAR) in a rat-to-presensitized mouse heart transplantation model and whether these mAb, combined with cyclosporine (CsA) and cyclophosphamide (CyP), can achieve long-term graft survival. METHODS: BALB/c mice were presensitized with 2x10(7) splenocytes from Lewis rats 14 days before grafting. Heart grafts from Lewis rats were heterotopically transplanted into BALB/c mice. Presensitized mice were treated with either anti-C5 mAb or a combination of anti-C5 mAb, CsA, and CyP. Controls included: presensitized mice with no treatment, presensitized mice treated with either CsA + CyP or IgG, and nonpresensitized mice with either no treatment or with CsA + CyP treatment. RESULTS: Although typical features of HAR were evident in the presensitized grafts, the mAb completely inhibited complement activation and successfully prevented HAR. Despite complement inactivation, the graft was rejected on postoperative day 6 with acute vascular rejection (AVR) also known as delayed xenograft rejection (DXR). Notably, this type of rejection cannot be effectively overcome by CsA and CyP. CONCLUSIONS: We conclude that (1) anti-C5 mAb prevents HAR, (2) AVR/DXR still occurs when HAR is prevented by complement inactivation, and (3) AVR/DXR cannot be overcome by conventional immunosuppression. These data suggest that anti-C5 mAb may be valuable for preventing HAR in future clinical xenotransplantation and that additional interventions may be required to address AVR/DXR.

Acute Disease↗

PubMed1999

Pharmacokinetics of (-)-beta-D-dioxolane guanine and prodrug (-)-beta-D-2,6-diaminopurine dioxolane in rats and monkeys.

(-)-beta-D-Dioxolane guanine (DXG) is a nucleoside analog possessing potent activity against human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2), and hepatitis B virus (HBV) in vitro. Owing to the limited aqueous solubility of DXG, (-)-beta-D-2,6-diaminopurine dioxolane (DAPD), a more water-soluble prodrug of DXG, is being developed for clinical use. The purpose of this study was to characterize the pharmacokinetics of DXG after administration of DXG and DAPD to rats and monkeys. After intravenous administration of DXG, plasma concentrations of the nucleoside declined in a biexponential manner, with a terminal-phase half-life of 0.44 +/- 0.14 hr (mean +/- SD) in rats and 2.3 hr in monkeys. Total clearance of DXG was 4.28 +/- 0.99 liters/hr/kg in rats and 0.72 liters/hr/kg in monkeys. Renal excretion of unchanged DXG accounted for approximately 50% of total clearance in both species. Steady state volume of distribution of DXG was 2.30 liters/kg in rats and 1.19 liters/kg in monkeys. After intravenous administration of DAPD to rats, prodrug concentrations declined with a half-life of 0.37 +/- 0.11 hr. DXG was rapidly generated from DAPD, with approximately 61% of the dose of DAPD being converted to DXG. After administration of DAPD to monkeys, only concentrations of metabolite DXG could be determined owing to rapid conversion of DAPD to DXG during sample collection. The half-lives of DAPD and DXG after intravenous administration determined from urinary excretion data were 0.8 +/- 0.4 and 1.6 +/- 0.2 hr, respectively. Oral bioavailability of DAPD was estimated to be approximately 30%.

Administration, Oral↗

PubMed1999

Free radical scavenging and antioxidant activities of flavonoids extracted from the radix of Scutellaria baicalensis Georgi.

Free radical scavenging and antioxidant activities of baicalein, baicalin, wogonin and wogonoside, the four major flavonoids in the radix of Scutellaria baicalensis Georgi, were examined in different systems. ESR results showed that baicalein and baicalin scavenged hydroxyl radical, DPPH radical and alkyl radical in a dose-dependent manner, while wogonin and wogonoside showed subtle or no effect on these radicals. Ten micromol/l of baicalein and baicalin effectively inhibited lipid peroxidation of rat brain cortex mitochondria induced by Fe(2+)-ascorbic acid, AAPH or NADPH, while wogonin and wogonoside showed significant effects only on NADPH-induced lipid peroxidation. In a study on cultured human neuroblastoma SH-SY5Y cells system, it was found that 10 micromol/l of baicalein and baicalin significantly protected cells against H(2)O(2)-induced injury. Baicalein was the most effective antioxidant among the four tested compounds in every system due to its o-tri-hydroxyl structure in the A ring. Compared with a well-known flavonoid, quercetin, the antioxidant activity of baicalein was lower in DPPH or AAPH system, but a little higher in those systems which might associate with iron ion. These results suggest that flavonoids in the radix of Scutellaria baicalensis with o-di-hydroxyl group in A the ring, such as baicalein and baicalin, could be good free radical scavengers and might be used to cure head injury associated with free radical assault.

Animals↗

PubMed1999

[The significance of TT virus detection in persons with elevated alanine aminotransferase during routine medical check up and patients with liver diseases].

OBJECTIVE: To investigate the significance of the new DNA virus (TTV) infection in persons with elevated alanine aminotransferase (ALT) during routine medical check up and patients with liver diseases, and analyze its pathogenesis. METHODS: PCR was used in the detection of TTV DNA in 19 serum samples from ALT elevated persons and 41 from ALT normal persons during their routine medical check up, and 182 serum samples from patients with various kinds of liver diseases. PCR products were confirmed by RFLP. Other hepatitis viruses were simultaneously detected using routine methods. RESULTS: TTV DNA was detected in 10.53% (2/19) and 2.44% (1/41) in groups of ALT elevated and control respectively with no significant difference between their detective rates (P > 0.05). There were 9 cases with current HBV infection, 1 case with hepatitis C and 1 case with hepatitis A in group of elevated ALT. Two TTV positive cases were both superinfected with HBV. The detecting rate of TTV DNA in patients with liver diseases was 4.4%. Only one case out of 18 non A to G hepatitis showed TTV DNA in serum. CONCLUSION: There were TTV infections in Chinese population. The main cause for ALT elevation in persons during routine medical check up was HBV infection. There were TTV infections in patients with liver diseases too. However, TTV wasn't the main cause of non A to G hepatitis. Thus, the pathogenesis of TTV might be very weak.

Alanine Transaminase↗

PubMed1999

Palmitoylation of the recombinant human A1 adenosine receptor: enhanced proteolysis of palmitoylation-deficient mutant receptors.

Palmitoylation of the recombinant human A(1) adenosine receptor (A(1)AR) expressed in HEK-293 cells is demonstrated by showing that hexahistidine (His(6))/Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys (FLAG) (H/F) A(1)ARs, purified to homogeneity from cells metabolically labelled with [(3)H]palmitate, incorporate tritium into a 38-42 kDa receptor glycoprotein. The amount of palmitoylation is not affected by incubation of cells with the A(1)AR-selective agonist N(6)-cyclopentyladenosine (CPA). A(1)AR palmitoylation is abolished by treatment with neutral hydroxylamine or by mutation of Cys-309 to Ala (C(309)-->A). Based on Western blotting and pulse-chase experiments with [(35)S]methionine, at least 90% of wild-type receptors are palmitoylated and turn over with a t1/2 of 6.4 h. Of the C(309)-->A mutated receptors, 40% appear to turn over like wild-type receptors, with a t1/2 of 7.1 h, and 60% appear to be rapidly cleaved to form a 25 kDa receptor fragment that turns over with a t1/2 of 0.8 h. In HEK-293 cell lines expressing similar numbers of wild-type or C(309)-->A mutant A(1)Rs, there is little difference in the kinetics of CPA-induced receptor internalization (1 h), down-regulation (24 h), inhibition of forskolin-stimulated cAMP accumulation, or activation of co-transfected G-protein-activated inward rectifier K(+)/cardiac inward rectifying K(+) (GIRK1/CIR K(+)) channels. Also unaffected by palmitoylation is guanosine 5'-[gamma-thio]-triphosphate ([S]GTP)-sensitive binding to membranes by the agonist (125)I-labelled aminobenzyladenosine. The results suggest that palmitoylation has little effect on receptor-effector coupling, agonist-induced internalization or down-regulation. We speculate that palmitoylation may divert newly synthesized A(1)ARs from a pathway leading to rapid degradation.

Adenosine↗

PubMed1999

Tumor-specific expression of anti-mdr1 ribozyme selectively restores chemosensitivity in multidrug-resistant colon-adenocarcinoma cells.

P-glycoprotein (Pgp)-conferred multidrug resistance (MDR) is expressed in cancer and in normal colon tissues and has important physiological functions. In order to selectively reverse MDR in malignant tissue without disrupting the function of normal colonocytes, a retroviral vector (pCEAMR) containing anti-mdr1 ribozyme coupled to the carcino-embryonic-antigen (CEA) promoter was constructed and introduced into resistant colon-cancer cells (SW1116R) that produce CEA and into control resistant cells (HeLaK) that do not produce CEA. Anti-mdr1 ribozyme was expressed in SW1116R cells but not in HeLaK cells. Subsequently, the expression of mdr1 mRNA and Pgp decreased significantly in the transfected SW1116R cells, and was even lower than in parent non-resistant SW1116 cells. The functional ability of Pgp to facilitate rhodamine 123 (Rh123) efflux showed that the transfected SW1116R cells with low Pgp expression retained Rh123, whereas non-transfected SW1116R cells with high Pgp expression released the dye quickly. There was no difference in mdr1 mRNA or in Pgp between non-transfected and transfected HeLaK cells. Drug resistance to doxorubicin (DOX) decreased 93.1% in the transfected SW1116R cells, while no change in drug resistance occurred in the infected HeLaK cells. DOX could clearly inhibit the growth of transfected SW1116R tumors but had no effect on untransfected and on transfected HeLaK cells in vivo. These results indicate that our anti-mdr1 ribozyme is expressed only in CEA-producing colon-cancer cells and reverses their drug resistance selectively.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

The mast cell tumor necrosis factor alpha response to FimH-expressing Escherichia coli is mediated by the glycosylphosphatidylinositol-anchored molecule CD48.

Mast cells are well known for their harmful role in IgE-mediated hypersensitivity reactions, but their physiological role remains a mystery. Several recent studies have reported that mast cells play a critical role in innate immunity in mice by releasing tumor necrosis factor alpha (TNF-alpha) to recruit neutrophils to sites of enterobacterial infection. In some cases, the mast cell TNF-alpha response was triggered when these cells directly bound FimH on the surface of Escherichia coli. We have identified CD48, a glycosylphosphatidylinositol-anchored molecule, to be the complementary FimH-binding moiety in rodent mast cell membrane fractions. We showed that (i) pretreatment of mast cell membranes with antibodies to CD48 or phospholipase C inhibited binding of FimH+ E. coli, (ii) FimH+ E. coli but not a FimH- derivative bound isolated CD48 in a mannose-inhibitable manner, (iii) binding of FimH+ bacteria to Chinese hamster ovary (CHO) cells was markedly increased when these cells were transfected with CD48 cDNA, and (iv) antibodies to CD48 specifically blocked the mast cell TNF-alpha response to FimH+ E. coli. Thus, CD48 is a functionally relevant microbial receptor on mast cells that plays a role in triggering inflammation.

Adhesins, Bacterial↗

PubMed1999

Purification of A1 adenosine receptor-G-protein complexes: effects of receptor down-regulation and phosphorylation on coupling.

We examined the effects of exposing A1 adenosine receptors (A1ARs) to an agonist on the stability and phosphorylation state of receptor-guanine nucleotide-binding regulatory protein (R-G-protein) complexes. Non-denatured recombinant human A1ARs extended on the N-terminus with hexahistidine (His6) and the FLAG (Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys) epitope (H/F) were purified to near homogeneity from stably transfected Chinese-hamster ovary (CHO)-K1 cells. Purified receptors have pharmacological properties similar to receptors in membranes. G-proteins were co-purified with 15+/-2% of H/F-A1AR unless receptor-G-protein (R-G) complexes were uncoupled by pre-treating cell membranes with GTP. By silver staining, purified A1AR-G-protein complexes contain receptors, G-protein alpha and beta subunits and an unidentified 97 kDa protein. Pretreating intact cells with N6-cyclopentyladenosine (CPA) for 24 h decreased both the total number of receptors measured in membranes and the number of purified A1ARs by about 50%. In contrast, pretreating cells with CPA decreased the number of R-G complexes measured in membranes (54+/-6%) significantly less than it decreased the number of purified R-G complexes (78+/-3%) as detected by 125I-N6-(4-aminobenzyl)adenosine binding or by Western blotting Gialpha2. The effect of CPA to decrease the fraction of receptors purified as R-G complexes was not associated with any change in low-level A1AR phosphorylation (found on serine), or low-level phosphorylation of G-protein alpha or beta subunits or the 97 kDa protein. These experiments reveal a novel aspect of agonist-induced down-regulation, namely a diminished stability of receptor-G-protein complexes that is manifested as uncoupling during receptor purification.

Animals↗

PubMed1999

A2B adenosine and P2Y2 receptors stimulate mitogen-activated protein kinase in human embryonic kidney-293 cells. cross-talk between cyclic AMP and protein kinase c pathways.

Mitogen-activated protein kinase (MAPK) cascades underlie long-term mitogenic, morphogenic, and secretory activities of purinergic receptors. In HEK-293 cells, N-ethylcarboxamidoadenosine (NECA) activates endogenous A2BARs that signal through Gs and Gq/11. UTP activates P2Y2 receptors and signals only through Gq/11. The MAPK isoforms, extracellular-signal regulated kinase 1/2 (ERK), are activated by NECA and UTP. H-89 blocks ERK activation by forskolin, but weakly affects the response to NECA or UTP. ERK activation by NECA or UTP is unaffected by a tyrosine kinase inhibitor (genistein), attenuated by a phospholipase C inhibitor (U73122), and is abolished by a MEK inhibitor (PD098059) or dominant negative Ras. Inhibition of protein kinase C (PKC) by GF 109203X failed to block ERK activation by NECA or UTP, however, another PKC inhibitor, Ro 31-8220, which unlike GF 109203X, can block the zeta-isoform, and prevents UTP- but not NECA-induced ERK activation. In the presence of forskolin, Ro 31-8220 loses its ability to block UTP-stimulated ERK activation. PKA has opposing effects on B-Raf and c-Raf-1, both of which are found in HEK-293 cells. The data are explained by a model in which ERK activity is modulated by differential effects of PKC zeta and PKA on Raf isoforms.

Animals↗

PubMed1999

Internalization of FimH+ Escherichia coli by the human mast cell line (HMC-1 5C6) involves protein kinase C.

Rodent mast cells (MC) play critical roles in host defense against bacterial infection. However, bacteria-mediated signaling mechanisms in MC have not been studied. In addition, the response of human MC to bacteria is not fully investigated. This study examined the interaction between human MC and type 1 fimbriated Escherichia coli and the mechanisms involved using the human MC line HMC-1 5C6 and human cord blood-derived MC. These MC internalized significant numbers of FimH+ E. coli, but not its isogenic FimH- mutant. In HMC-1 cells, bacterial internalization was stimulated by protein kinase C (PKC) activation [short-term phorbol myristate acetate (PMA) treatment] and dramatically decreased by PKC inhibitors or PKC depletion (long-term PMA treatment). Moreover, bacterial internalization was accompanied by significant expression of PKCbeta1 and delta. Fluorescence microscopy demonstrated accumulation of PKCbeta1 on internalized bacteria. These data indicate that human MC has the capacity to internalize bacteria and PKC may be a critical intracellular mediator of this function.

Adhesins, Bacterial↗

PubMed1999

Bacteria-host cell interaction mediated by cellular cholesterol/glycolipid-enriched microdomains.

Gram negative bacterial infection is a leading cause of fatality and is attributed, at least in part, to the bacteria's capacity to persist in the host in spite of appropriate antibiotic therapy. It has been suggested that bacteria evade antibiotics by hiding within host cells. We sought to investigate this important aspect of infections in mast cells, which are inflammatory cells found in close proximity to the host-environment interface and which have recently been reported to play a crucial role in the early innate immune response to bacteria. We examined mast cell interactions with FimH-expressing E. coli, one of the major opportunistic pathogens of humans. We determined that in serum free conditions, these bacteria were able to trigger mast cell uptake without loss of bacterial viability. CD48, a mannose containing GPI (glycosylphosphatidylinositol)-linked molecule was found to be the receptor of FimH-expressing E. coli in mouse mast cells. We found that the internalization via CD48 was blocked by filipin, a cholesterol binding drug known to disrupt cholesterol/glycolipid-enriched microdomains and the bacteria-encasing vacuoles were rich in cholesterol inside cells. Interestingly, we found that mast cells subsequently expelled majority of the intracellular bacteria in 24 hours. This expulsion process was blocked by lovastatin/cyclodextrin treatment, which is known to inhibit cellular trafficking of cholesterol/glycolipid-enriched microdomains. Thus, the bacterial entry into and expulsion from mast cells were critically dependent on cholesterol/glycolipid-enriched microdomains, which represents a novel mode of tussle between the pathogen and the mast cell occurring in opsonin deficient sites in the body or even at other sites in naive or immunocompromised hosts which have low systemic levels of E. coli specific antibody.

Adhesins, Bacterial↗