[Best evidence summary for awake prone positioning in treating hypoxemic due to COVID-19 infection]

Objective: To retrieve, evaluate, and summarize the best evidence for the treatment of hypoxemia in patients with COVID-19 infection using the awake prone positioning, with the aim of guiding healthcare professionals in the standardized implementation of this therapy. Methods: A systematic search was conducted in databases including UpToDate, BMJ Best Practice, JBI Evidence-Based Healthcare Center, American Association of Critical-Care Nurses, Intensive Care Society, European Respiratory Society, World Health Organization website, Cochrane Library, PubMed, China National Knowledge Infrastructure (CNKI), and Wanfang. The retrieved literature was subjected to quality assessment and evidence extraction. Results: A total of ten publications were included, consisting of one thematic evidence summary, one guideline, two systematic reviews, three randomized controlled trials, and three expert consensus statements. This summary synthesizes thirty key pieces of evidence in five categories: organizational management and training, risk assessment, preparatory operations, implementation key points, and risk control. Conclusions: Awake prone positioning is beneficial for improving hypoxemia in patients with COVID-19 and is easy to implement. Medical institutions should develop nursing management systems, operational standards, and best practices for awake prone positioning based on evidence-based evidence in order to improve the quality of care management for such patients.

CUL4A promotes the invasion of cervical cancer cells by regulating NF-κB signaling pathway

OBJECTIVE

The aim of this study was to investigate the effects of cullin 4A (CUL4A) on promoting the proliferation and inhibiting the apoptosis of cervical cancer (CC) cells by regulating the nuclear factor-kappa B (NF-κB) signaling pathway.

PATIENTS AND METHODS

The protein expressions of CUL4A and NF-κB in 75 CC tissues were detected through immunohistochemistry. The correlation between the expressions of the two proteins in CC tissues was analyzed via Spearman's correlation test. Meanwhile, the prognostic significance of CUL4A expression for CC patients was analyzed by Kaplan-Meier curve. CUL4A small interfering ribonucleic acid (siRNA) was transfected into CC cells (HeLa) to downregulate the expression level of CUL4A. Subsequently, the effects of CUL4A on the proliferation and apoptosis of HeLa cells were detected by methyl thiazolyl tetrazolium (MTT) assay and flow cytometry, respectively. Finally, the effect of CUL4A on the activity of the NF-κB signaling pathway was analyzed through quantitative Real Time-Polymerase Chain Reaction (qRT-PCR).

RESULTS

The protein expressions of CUL4A and NF-κB in CC tissues were significantly higher than those in normal tissues (p<0.01). The results of the survival curve showed that the prognosis of CC patients with highly expressed CUL4A is poor (p<0.001). Meanwhile, lowly expressed CUL4A protein significantly inhibited the proliferation and promoted the apoptosis of HeLa cells (p<0.01). QRT-PCR results indicated that the relative messenger RNA (mRNA) expression levels of downstream genes of the NF-κB signaling pathway were significantly lower in CC cells than those in the control group (p<0.001). In addition, CUL4A expression was positively correlated with NF-κB expression in CC (p<0.001).

CONCLUSIONS

CUL4A promotes the invasion of CC cells through the NF-κB signaling pathway.

A New Global Variance Reduction Technique Based on Geometry and Energy Splitting/Roulette

With the increase of computer resources and the application of global variance reduction (GVR) method, it is a trend to obtain global distribution using the Monte Carlo (MC) method in deep-penetration shielding calculation. GVR technique uses biased source and weight window to decrease the MC calculation tally error for deep-penetration problems. However, excessive splitting of large weight particles out of the source region is time-consuming for problems with significant fluence rate variation. A new GVR technique, which performs space and energy splitting/roulette based on the importance of the phase space, is proposed in this paper to avoid excessive splitting of large weight particles. The improved GVR technique is applied to the H. B. Robinson Unit 2 (HBR-2) benchmark and CAP1400 dose rate distribution calculation. Numerical results show that the new GVR technique shows excellent performance for deep-penetration shielding calculation.

Chemoembolisation with polyvinyl alcohol for advanced hepatocellular carcinoma with portal vein tumour thrombosis and arterioportal shunts: efficacy and prognostic factors

AIM

To evaluate the efficacy and to identify prognostic factors of polyvinyl alcohol (PVA) chemoembolisation for treating advanced hepatocellular carcinoma (HCC) with portal vein (PV) tumour thrombosis (PVTT) and arterioportal shunts.

MATERIALS AND METHODS

The clinical data of 145 advanced HCC patients with PVTT and arterioportal shunts were collected. The patients were divided into two groups: group A, with main PV invasion, (n=56) and group B, with PV branch invasion, (n=89). Based on arterioportal shunt types, different particle sizes of PVA were used for chemoembolisation. The overall survival (OS), time to progression (TTP), and postoperative complications were analysed retrospectively.

RESULTS

The median OS of all patients was 10.1 months. The median OS of group A and group B was 8.2 and 12.5 months, respectively (χ²=6.03, p=0.01). The overall 6-, 12-, and 18-month survival rates of groups A and B were 63.8%, 24.9%, and 6.3%, and 78.1%, 55.2%, and 23.7%, respectively. After embolisation, there were two cases of acute liver failure and three cases of upper gastrointestinal bleeding. Cox multivariate survival analysis revealed that main PVTT (HR [hazard ratio]=1.75, p=0.01), Child-Pugh B class (HR=1.99, p=0.003) and tumour burden ≥50% (HR=3.25, p<0.001) were independent risk factors. A dose of oxaliplatin >100 mg (HR=0.48, p<0.001) was an independent protection factor.

CONCLUSION

Treatment of advanced HCC with PVTT and arterioportal shunts by PVA chemoembolisation is safe and effective. The patients achieved a better prognosis with the dose of oxaliplatin >100 mg, while main PVTT, Child-Pugh B class, and tumour burden ≥50% were poor prognostic indicators.

The association between the UBQLN1 polymorphism and Alzheimer's disease risk: A systematic review

Recently, some studies suggested that UBQLN1 variant was associated with AD risk. However, the results were inconsistent. This meta-analysis aimed to determine the association between UBQLN1 variant and AD risk. We searched the electronic databases PubMed, Embase, and CNKI databases. Random-effects model was used. All statistical tests were performed using the STATA 11.0 software (StataCorp, College Station, TX, USA). UBQLN1 variant was not associated with the risk of AD (OR=1.05; 95%CI, 0.92-1.19; I2=35%). The corresponding pooled ORs were not materially altered in sensitivity analysis. The Galbraith plot was used to find the source of the heterogeneity and no study was the outlier. The shape of the funnel plot showed symmetry. Egger's test found no evidence of publication bias (P=0.8). These results suggest that the UBQ-8i polymorphism was not associated with AD risk.

Testing the mutant selection window hypothesis in vitro and in vivo with Staphylococcus aureus exposed to fosfomycin

The purpose of this study was to test the mutant selection window (MSW) hypothesis in vitro and in vivo with Staphylococcus aureus exposed to fosfomycin. With the in vitro time-kill studies, S. aureus ATCC 29213 [with a minimal concentration that inhibits colony formation by 99% (MIC99) of 2.2 μg/mL and a mutant prevention concentration (MPC) of 57.6 μg/mL] lost fosfomycin susceptibility at antibiotic concentrations (2×, 4×, and 8× MIC) that are between the lower and upper boundaries of the MSW. In the tissue-cage model, S. aureus was exposed to fosfomycin pharmacokinetics at concentrations below the MIC99, between the MIC99 and the MPC, and above the MPC, respectively. Changes in susceptibility and counts of total and resistant viable bacteria were monitored in tissue-cage fluid obtained daily. However, the selection of resistant mutants was not observed during antibacterial treatment and 48 h after the termination of fosfomycin treatment, regardless of the fosfomycin dosage. Besides, we found no differences between the in vitro-isolated mutant and its sensitive parental strain, which indicates the absence of fitness cost of fosfomycin resistance in S. aureus ATCC 29213. These findings demonstrate that agar plate determinations do not fit the MSW for fosfomycin treatment of rabbits infected with S. aureus ATCC 29213; therefore, the existence of the window must be demonstrated not only in vitro but also in vivo. Further research is needed on the exact mechanism of resistance.

Subtypes of major depression: latent class analysis in depressed Han Chinese women

BACKGROUND

Despite substantial research, uncertainty remains about the clinical and etiological heterogeneity of major depression (MD). Can meaningful and valid subtypes be identified and would they be stable cross-culturally?

METHOD

Symptoms at their lifetime worst depressive episode were assessed at structured psychiatric interview in 6008 women of Han Chinese descent, age ⩾ 30 years, with recurrent DSM-IV MD. Latent class analysis (LCA) was performed in Mplus. RESULTS; Using the nine DSM-IV MD symptomatic A criteria, the 14 disaggregated DSM-IV criteria and all independently assessed depressive symptoms (n = 27), the best LCA model identified respectively three, four and six classes. A severe and non-suicidal class was seen in all solutions, as was a mild/moderate subtype. An atypical class emerged once bidirectional neurovegetative symptoms were included. The non-suicidal class demonstrated low levels of worthlessness/guilt and hopelessness. Patterns of co-morbidity, family history, personality, environmental precipitants, recurrence and body mass index (BMI) differed meaningfully across subtypes, with the atypical class standing out as particularly distinct.

CONCLUSIONS

MD is a clinically complex syndrome with several detectable subtypes with distinct clinical and demographic correlates. Three subtypes were most consistently identified in our analyses: severe, atypical and non-suicidal. Severe and atypical MD have been identified in multiple prior studies in samples of European ethnicity. Our non-suicidal subtype, with low levels of guilt and hopelessness, may represent a pathoplastic variant reflecting Chinese cultural influences.

The structure of the symptoms of major depression: exploratory and confirmatory factor analysis in depressed Han Chinese women

BACKGROUND

The symptoms of major depression (MD) are clinically diverse. Do they form coherent factors that might clarify the underlying nature of this important psychiatric syndrome?

METHOD

Symptoms at lifetime worst depressive episode were assessed at structured psychiatric interview in 6008 women of Han Chinese descent, age ⩾30 years with recurrent DSM-IV MD. Exploratory factor analysis (EFA) and confirmatoryfactor analysis (CFA) were performed in Mplus in random split-half samples.

RESULTS

The preliminary EFA results were consistently supported by the findings from CFA. Analyses of the nine DSM-IV MD symptomatic A criteria revealed two factors loading on: (i) general depressive symptoms; and (ii) guilt/suicidal ideation. Examining 14 disaggregated DSM-IV criteria revealed three factors reflecting: (i) weight/appetite disturbance; (ii) general depressive symptoms; and (iii) sleep disturbance. Using all symptoms (n = 27), we identified five factors that reflected: (i) weight/appetite symptoms; (ii) general retarded depressive symptoms; (iii) atypical vegetative symptoms; (iv) suicidality/hopelessness; and (v) symptoms of agitation and anxiety.

CONCLUSIONS

MD is a clinically complex syndrome with several underlying correlated symptom dimensions. In addition to a general depressive symptom factor, a complete picture must include factors reflecting typical/atypical vegetative symptoms, cognitive symptoms (hopelessness/suicidal ideation), and an agitated symptom factor characterized by anxiety, guilt, helplessness and irritability. Prior cross-cultural studies, factor analyses of MD in Western populations and empirical findings in this sample showing risk factor profiles similar to those seen in Western populations suggest that our results are likely to be broadly representative of the human depressive syndrome.

c-Myc-mediated repression of miR-15-16 in hypoxia is induced by increased HIF-2α and promotes tumor angiogenesis and metastasis by upregulating FGF2

Previous studies have established the link between aberrant microRNA (miRNA) expression and hypoxia in various neoplasms. However, how these hypoxia-related miRNAs modulate tumor progression is still unclear. Therefore, the patterns of miRNA in colorectal carcinoma cell lines in response to hypoxia or not were first screened and the hypoxia-induced repression of the miR-15-16 cluster was confirmed. Then, this repression was found to be associated with high tumor stage and poor prognosis in colorectal carcinoma and is shown to promote tumor angiogenesis and metastasis by the loss of restriction of its target gene, fibroblast growth factor-2 (FGF2). Moreover, the general and alterative promoters of the miR-15-16 host (deleted in lymphocytic leukemia 2, DLEU2) were mapped, and three c-Myc/Max binding sites in response to the hypoxia-induced repression of miR-15-16 were further identified. Finally, an enhanced stability of c-Myc/Max heterodimer promoted by increased hypoxia-inducible factor-2α (HIF-2α) was validated, and we also verified that the enhancement contributed to the hypoxia-induced repression of miR-15-16. In brief, the c-Myc-mediated transcriptional repression of miR-15-16 in hypoxia is induced by increased HIF-2α and promoted tumor angiogenesis and hematogenous metastasis by the further loss of post-transcriptional inhibition of FGF2. Our study provides a better understanding of the coping mechanisms in response to tumor hypoxia and may be helpful in developing an effective prognostic marker or treatment target against solid tumors.

Cognitive trio: relationship with major depression and clinical predictors in Han Chinese women

BACKGROUND

Previous studies support Beck's cognitive model of vulnerability to depression. However, the relationship between his cognitive triad and other clinical features and risk factors among those with major depression (MD) has rarely been systematically studied.

METHOD

The three key cognitive symptoms of worthlessness, hopelessness and helplessness were assessed during their lifetime worst episode in 1970 Han Chinese women with recurrent MD. Diagnostic and other risk factor information was assessed at personal interview. Odds ratios (ORs) were calculated by logistic regression.

RESULTS

Compared to patients who did not endorse the cognitive trio, those who did had a greater number of DSM-IV A criteria, more individual depressive symptoms, an earlier age at onset, a greater number of episodes, and were more likely to meet diagnostic criteria for melancholia, postnatal depression, dysthymia and anxiety disorders. Hopelessness was highly related to all the suicidal symptomatology, with ORs ranging from 5.92 to 6.51. Neuroticism, stressful life events (SLEs) and a protective parental rearing style were associated with these cognitive symptoms.

CONCLUSIONS

During the worst episode of MD in Han Chinese women, the endorsement of the cognitive trio was associated with a worse course of depression and an increased risk of suicide. Individuals with high levels of neuroticism, many SLEs and high parental protectiveness were at increased risk for these cognitive depressive symptoms. As in Western populations, symptoms of the cognitive trio appear to play a central role in the psychopathology of MD in Chinese women.

Rapid reuptake of granzyme B leads to emperitosis: an apoptotic cell-in-cell death of immune killer cells inside tumor cells

A cell-in-cell process refers to the invasion of one living cell into another homotypic or heterotypic cell. Different from non-apoptotic death processes of internalized cells termed entosis or cannibalism, we previously reported an apoptotic cell-in-cell death occurring during heterotypic cell-in-cell formation. In this study, we further demonstrated that the apoptotic cell-in-cell death occurred only in internalized immune killer cells expressing granzyme B (GzmB). Vacuole wrapping around the internalized cells inside the target cells was the common hallmark during the early stage of all cell-in-cell processes, which resulted in the accumulation of reactive oxygen species and subsequent mitochondrial injury of encapsulated killer or non-cytotoxic immune cells. However, internalized killer cells mediated rapid bubbling of the vacuoles with the subsequent degranulation of GzmB inside the vacuole of the target cells and underwent the reuptake of GzmB by killer cells themselves. The confinement of GzmB inside the vacuole surpassed the lysosome-mediated cell death occurring in heterotypic or homotypic entosis processes, resulting in a GzmB-triggered caspase-dependent apoptotic cell-in-cell death of internalized killer cells. On the contrary, internalized killer cells from GzmB-deficient mice underwent a typical non-apoptotic entotic cell-in-cell death similar to that of non-cytotoxic immune cells or tumor cells. Our results thus demonstrated the critical involvement of immune cells with cytotoxic property in apoptotic cell-in-cell death, which we termed as emperitosis taken from emperipolesis and apoptosis. Whereas entosis or cannibalism may serve as a feed-on mechanism to exacerbate and nourish tumor cells, emperitosis of immune killer cells inside tumor cells may serve as an in-cell danger sensation model to prevent the killing of target cells from inside, implying a unique mechanism for tumor cells to escape from immune surveillance.

Rac1 is crucial for Ras-dependent skin tumor formation by controlling Pak1-Mek-Erk hyperactivation and hyperproliferation in vivo

Rac1 has a role in proliferation and survival of tumor cells in vitro. The exact effects of Rac1 on growth, apoptosis and corresponding signaling pathways during tumorigenesis in vivo, however, have not been explored yet. Using mice with a keratinocyte-restricted deletion of the Rac1 gene, we found that Rac1 is essential for DMBA/TPA-induced skin tumor formation. This corresponded to a decreased keratinocyte hyperproliferation, although apoptosis was not detectably altered. Activated Rac1 promoted Erk-dependent hyperproliferation by Pak1-mediated Mek activation independent of Mek1 phosporylation at serine 298. Rac1 was furthermore required for Pak2-dependent hyperactivation of Akt, which under in vivo condition was restricted to the suprabasal cell layers corresponding to a suprabasal-specific expression of Pak2. It is surprising that none of these signaling pathways was altered in untreated Rac1-deficient skin, indicating a hyperproliferation-specific function of Rac1 in vivo. These data suggest that blocking of Rac1 function might allow tumor-specific growth repression, as Rac1 is not required for normal growth and growth signaling controlling pathways in skin in vivo.

Loss of islet sympathetic nerves and impairment of glucagon secretion in the NOD mouse: relationship to invasive insulitis

AIMS/HYPOTHESIS

We hypothesised that non-obese diabetic mice (NOD) mice have an autoimmune-mediated loss of islet sympathetic nerves and an impairment of sympathetically mediated glucagon responses. We aimed: (1) to determine whether diabetic NOD mice have an early impairment of the glucagon response to insulin-induced hypoglycaemia (IIH) and a coincident loss of islet sympathetic nerves; (2) to determine whether invasive insulitis is required for this nerve loss; and (3) to determine whether sympathetically mediated glucagon responses are also impaired.

METHODS

We measured glucagon responses to both IIH and tyramine in anaesthetised mice. We used immunohistochemistry to quantify islet sympathetic nerves and invasive insulitis.

RESULTS

The glucagon response to IIH was markedly impaired in NOD mice after only 3 weeks of diabetes (change, -70%). Sympathetic nerve area within the islet was also markedly reduced at this time (change, -66%). This islet nerve loss was proportional to the degree of invasive insulitis. More importantly, blocking the infiltration prevented the nerve loss. Mice with autoimmune diabetes had an impaired glucagon response to sympathetic nerve activation, whereas those with non-autoimmune diabetes did not.

CONCLUSIONS/INTERPRETATION

The invasive insulitis seen in diabetic NOD mice causes early sympathetic islet neuropathy. Further studies are needed to confirm that early sympathetic islet neuropathy is responsible for the impaired glucagon response to tyramine.

Analysis of high-energy x-ray diffraction data at high pressure: the case of vitreous As2O3 at 32 GPa

The x-ray structure factor of vitreous As₂O₃ has been measured at 32 GPa in a laser-perforated diamond anvil cell using a monochromatic, micro-focused high-energy x-ray beam. The experimental correction procedures are discussed in detail, and they yield reliable data over the range Q = 0.3-13.5 Å^-1. The use of modified form factors to analyse the scattering data is presented to account for charge transfer. Analysis of the radial distribution function yields an increase in the coordination number from 3.1 ± 0.3 oxygen atoms surrounding an arsenic atom at normal pressure to 4.8 ± 0.5 at 32 GPa with only a slight change in the As-O bond length. Substantial structural changes are observed at higher distances, extending up to 18 Å in real space.

Comment on 'Microscopic structural evolution during the liquid-liquid transition in triphenyl phosphite' by R Kurita, Y Shinohara, Y Amemiya and H Tanaka J. Phys.: Condens. Matter 19 (2007) 152101

In the communication by Kurita et al 2007 J. Phys.: Condens. Matter 19 152101, peaks in the liquid diffraction pattern of triphenyl phosphite have been attributed to intermolecular phosphor-phosphor distances. Based on our previous neutron and x-ray diffraction studies we argue that this assignment is incorrect and the peak contributions are likely to be much more complex.

Germline hMSH2 promoter mutation in a Chinese HNPCC kindred: evidence for dual role of LOH

Hereditary non-polyposis colorectal cancer (HNPCC) is a dominantly inherited cancer predisposition syndrome that is caused by germline mutations in mismatch repair genes. By screening the core promoters of hMSH2, hMLH1, and hMSH6 in 37 Chinese suspected HNPCC families, a novel germline mutation c.-78_-79delGT was found in the hMSH2 promoter. Its pathogenic effects were supported by the following findings: (a) it co-segregated with HNPCC-related cancers and was not present in the 220 control subjects, (b) tumors harboring the mutation lacked the expression of hMSH2 and showed high microsatellite instability, (c) it significantly decreased the promoter activity, and (d) it abolished the binding ability of the transcription factor E1A-F. Loss of heterozygosity (LOH) was found in three of the tumors studied. Intriguingly, in the tumors from patients II:1 and III:1, LOH occurred in the wild-type allele and agreed well with the traditional 'two-hit' model. In contrast, in the tumor from patient III:3, LOH occurred in the mutant allele. A pathogenic somatic mutation (c.2210+1G>A) was also found in this tumor; therefore, we proposed that the 'second hit' was inactivated by somatic mutation, and the mutant allele was lost during tumor progression; this provided evidence for the new hypothesis for the dual role of LOH.

Structure of liquid SiO2: a measurement by high-energy x-ray diffraction

The x-ray structure factor for liquid SiO2 has been measured by laser heating of an aerodynamically levitated droplet. The main structural changes of the melt compared to the room temperature glass are associated with an increase in the size of the SiO4 tetrahedra, indicating a small reduction in the average Si-O-Si bond torsion angle and an expansion of the network between 5 and 9 A. Strong directional bonds with little high temperature broadening and a high degree of intermediate range order are found to persist in the liquid state.

Orientational Correlations in the Glacial State of Triphenyl Phosphite

Spallation neutron and high-energy X-ray diffraction experiments have been performed to investigate the local structure of the glacial and supercooled liquid states in triphenyl phosphite. The observed diffraction patterns have been interpreted using a Reverse Monte Carlo modeling technique. The results show that the glacial state forms unusually weak intermolecular hydrogen bonds between an oxygen atom connected to a phenyl ring and an adjacent phenyl ring aligned in an approximately antiparallel configuration. The structure is very different from the hexagonal crystal which is characterized by two weaker hydrogen bonds between linear arrays of molecules which are offset from each other and packed in a hexamer arrangement.

Isotope quantum effects in water around the freezing point

We have measured the difference in electronic structure factors between liquid H(2)O and D(2)O at temperatures of 268 and 273 K with high energy x-ray diffraction. These are compared to our previously published data measured from 279 to 318 K. We find that the total structural isotope effect increases by a factor of 3.5 over the entire range, as the temperature is decreased. Structural isochoric temperature differential and isothermal density differential functions have been used to compare these data to a thermodynamic model based upon a simple offset in the state function. The model works well in describing the magnitude of the structural differences above approximately 310 K, but fails at lower temperatures. The experimental results are discussed in light of several quantum molecular dynamics simulations and are in good qualitative agreement with recent temperature dependent, rotationally quantized rigid molecule simulations.

Change of nitric oxide in experimental colitis and its inhibition by melatonin in vivo and in vitro

AIM

To investigate the change of nitric oxide (NO) in rat colitis and its inhibition by melatonin in vivo and in vitro.

METHODS

In vivo, rat colitis was established intracolonically with trinitrobenzenesulphonic acid (TNBS) and ethanol. The animals were randomised into five groups: control group, model group, melatonin group (2.5, 5.0, 10.0 mg/kg), and treated intracolonically with saline, saline and melatonin respectively (once a day, from day 7 after colitis was established to day 28). After the end of the experiment, the mucosal damage index (CMDI) and histology score (HS) were evaluated and the level of myeloperoxidase (MPO) and malondiadehyde (MDA) and NO in the colon tissue were measured. In vitro, the co-culture model of the inflamed colon mucosa (from the colitis) with lipopolysaccharide (LPS), and the colonocytes oxidative injury model by hydroxyl radical, were designed respectively to elucidate the inhibition of NO by melatonin.

RESULTS

After treated with TNBS/ethanol, the extent of CMDI and HS, the levels of MPO, MDA, and NO in the model group, were higher than that in the control group; melatonin ameliorated these parameters effectively. The stimulation of LPS increased the level of NO and MPO and MDA in the co-culture model of inflamed colon mucosa, and melatonin significantly reduced the level of MPO, MDA, and NO. In the coloncyte oxidative injury model by hydroxyl radical, the contents of LDH, MDA, and NO were increased; melatonin reversed this oxidative injury considerably.

CONCLUSION

This study showed that TNBS/ethanol induced colitis was pharmacologically controlled by melatonin in vivo and in vitro.

Autonomic mechanism and defects in the glucagon response to insulin-induced hypoglycaemia

In summary, this article briefly reviews the evidence that three separate autonomic inputs to the islet are capable of stimulating glucagon secretion and that each is activated during IIH. We have reviewed our evidence that these autonomic inputs mediate the glucagon response to IIH, both in non-diabetic animals and humans. Finally, we outline our new preliminary data suggesting an eSIN in an autoimmune animal model of T1DM. We conclude that the glucagon response to IIH is autonomically mediated in non-diabetic animals and humans. We further suggest that at least one of these autonomic inputs, the sympathetic innervation of the islet, is diminished in autoimmune T1DM. These data raise the novel possibility that an autonomic defect contributes to the loss of the glucagon response to IIH in T1DM.

[Pharmacokinetical study of safflor yellow on rat acute model of blood stasis syndrome]

OBJECTIVE

To study the pharmacokinetical character of safflor yellow in rat acute model of blood stasis syndrome.

METHODS

The rat acute model of blood stasis syndrome was made by i.p. adrenalin (0.07 ml/kg) and the stimulation of ice-water. At the time of 5, 10, 30, 60, 120, 180, 320, 480 min, the concentration of safflor yellow in the serum after i.v. safflor yellow (37.08 ml/kg) was determined.

RESULTS

The concentration-time date of safflor yellow in rat acute model of blood stasis syndrome was shown to fit a double-compartment open model, t1/2 alpha = 1.43 min, t1/2 beta = 95.65 min, AUC = 49,632.90 micrograms.min/ml; while the concentration-time data of safflor yellow in normal rat was shown to fit a single-compartment open model, t1/2 alpha = 66.27 min, AUC = 42,267 micrograms.min/ml.

CONCLUSION

The metabolism of safflor yellow was evidently later in rat acute model of blood stasis syndrome than in normal rat.

Fos expression in rat celiac ganglion: an index of the activation of postganglionic sympathetic nerves

To develop an index of the activation of abdominal sympathetic nerves, we used Fos immunostaining of the celiac ganglion (CG) taken from rats receiving nicotine, preganglionic nerve stimulation, or glucopenic agents. Subcutaneous nicotine injection moderately increased Fos expression in the principal ganglionic cells of the CG (17 +/- 4 Fos+ per mm(2), approximately 12% of all principal CG cells), whereas subcutaneous saline had no effect (0 +/- 0 Fos+ per mm(2); n = 7; P < 0.01). Greater Fos expression was obtained by applying nicotine topically to the CG (71 +/- 8 Fos+ per mm(2); 52% of all principal CG cells, n = 5; P < 0.01 vs. topical saline, n = 4) and by preganglionic nerve stimulation (126 +/- 9 Fos+ per mm(2); 94% of all principal CG cells, n = 11; P < 0.01 vs. nerve isolation, n = 7). Moderate Fos expression was also observed in the CG after intraperitoneal 2-deoxy-D-glucose (2DG) injection (21 +/- 2 Fos+ per mm(2); 16% of all principal CG cells, n = 5; P < 0.01 vs. saline ip) or insulin injection (16 +/- 2 Fos+ per mm(2); 12% of all principal CG cells, n = 6; P < 0.01 vs. saline ip). Furthermore, Fos expression induced by 2DG was dose and time dependent. These data demonstrate significant Fos expression in the CG in response to chemical, electrical, and reflexive stimulation. Thus Fos expression in the CG may be a useful index to describe various levels of activation of its postganglionic sympathetic neurons.

[Study on anti-inflammatory, analgesic and antipyretic effects of bagmaking tea of sanyaku]

OBJECTIVE

To observe anti-inflammatory, analgesic and antipyretic effects of the Bagmaking Tea of Sanyaku in rats.

METHODS

mouse torsion modle induced by glacial acetic acid, mouse auricle swelling model induced by xylene and rat fever model induced by baker yeast were used.

RESULTS

Bagmaking Tea of Sanyaku could inhibit mouse torsion action, mouse auricle swelling and rat fever.

CONCLUSION

Bagmaking Tea of Sanyaku possessed anti-inflammatory, analgesic and antipyretic effects.

Type 1 protein tyrosine kinases in Chinese breast carcinomas: a clinicopathologic study

Immunostaining for epidermal growth factor receptor (EGFR), c-erbB-2, c-erbB-3, c-erbB-4, ER, and PR was performed in 107 cases of primary breast carcinomas from Anyang, China. The expression rates of EGFR, c-erbB-2, c-erbB-3 and c-erbB-4 in this series were 43.9%, 36%, 27%, and 45.8%, respectively, and a stronger c-erbB-4 staining of "normal" glandular structures inside tumors and in the vicinity of tumor clusters was confirmed. Larger tumor size, lymph node metastases, and higher histologic grade in invasive ductal carcinomas were shown to be statistically valuable negative prognostic factors, and c-erbB-2 expression was also weakly associated with a poor prognosis no matter what the nodal status. The expressions of c-erbB-4 and ER in invasive ductal carcinomas were inversely associated with histologic grade of the tumors. Associations between the expression of c-erbB-4 and ER (p = 0.001) and the expression of ER and PR study (p = 0.004) were found in the present study. No significant associations between the expressions of EGFR, c-erbB-3, c-erbB-4, ER, and PR and overall survival were detected. The expression of c-erbB-4 in the node negative group was, however, associated with a better prognosis, indicating a different role of c-erbB-4 protein in breast tumor development than other EGFR family members have. Int J Surg Pathol 9(3):177-187, 2001

P2 purinergic receptor activation enhances cardiac contractility in isolated rat and mouse hearts

Activation of P2 purinergic receptors exerts a potent positive inotropic effect in the cardiac myocyte. However, it is unknown whether its activation can also cause an increased contractility in intact heart. With the use of isolated rat and mouse hearts, the objective of the present study was to investigate the effect of P2 receptor agonist on the function of the intact heart. In both Langendorff rat hearts and working rat and mouse heart models, the P2X receptor agonist 2-methylthio-ATP (2-meSATP) caused dose-dependent increases in left ventricular developed pressure, rate of contraction, and rate of relaxation. The extent of P2X receptor agonist-stimulated increase in contractility was significantly less than that stimulated by the beta-adrenergic agonist isoproterenol. However, the increase in contractility occurred without a significant effect on the basal heart rate, in contrast to that caused by isoproterenol. In isolated rat ventricular myocytes, both ATP and the P2X receptor agonist 2-meSATP stimulated large increases in the myocyte contractile amplitude (107 +/- 13% and 99 +/- 9%, n = 17 cells from 5 rats and n = 19 cells from 6 rats, respectively). 2-meSATP caused only a slight increase in phospholipase C activity and could stimulate myocyte contractility in the presence of phospholipase C inhibitor U-73122, consistent with the role of a phospholipase C-independent P2X receptor in mediating the positive inotropic effect of 2-meSATP. The data provide evidence for a potentially important physiological role of the cardiac P2X receptor and for the concept that agonist at this receptor may be beneficial for the treatment of cardiac dysfunction.

Human papillomavirus type 16 is an important infectious factor in the high incidence of esophageal cancer in Anyang area of China

To investigate the potential role of human papillomavirus (HPV) infection in the pathogenesis of esophageal carcinomas in the Anyang area of China, we have evaluated specimens collected by balloon cytology examination from volunteers in two regions with significantly different incidences of esophageal carcinoma. 138 donors were from a village in a county with an esophageal carcinoma (EC) age-adjusted mortality rate of 132x10(5), the remaining 68 were resident in a second village from another county with an EC mortality rate of 52x10(5). Specimens were evaluated using both polymerase chain reaction (PCR) amplification and in situ hybridization (ISH) protocols. PCR results showed that the prevalence of the human papillomavirus type 16 (HPV-16) E6 gene in the high incidence area was 1.9-fold higher than that of the low incidence area (72 and 37%, respectively, P < 0.01). Moreover, the positive rate corresponded with pathology grade. Similar results were obtained with the HPV-16 E7 gene. As the cells undergoing cytopathological progress, the HPV-16 E6 positive rate was increased, in both villages. In contrast to HPV-16 E6 and E7, detection of the HPV L1 gene was consistently lower, and its prevalence decreased with increasing dysplasia grades (P < 0.05). By ISH analyses, the expression rate of HPV-16 E6 in the specimens collected from the high incidence area was 2.2-fold higher than those from the low incidence area (49 versus 22%, respectively; P < 0.05), and transcription of the E6 gene paralleled cytopathology. HPV-18 was also detected in 17 and 15% of the specimens from the high and low incidence areas, respectively, but most of these samples were also simultaneously HVP-16 positive. These results suggest that HVP-16 plays a causative role in the high incidence of esophageal cancer in the Anyang region of CHINA:

[The effects of safflor yellow on microcirculation and hemorheology of acute blood stasis rats]

OBJECTIVE

To observe the effects of safflor yellow on microcirculation and hemorheology of acute blood stasis rats.

METHODS

The acute blood stasis medel was made by i.p. adrenalin (0.07 ml/(kg.time) for 2 times and the stimulation of ice-water.

RESULTS

Safflor could markedly improve the number of net dot in microcirculation, and eta b, eta p, eta f in hemorheology (P < 0.05).

CONCLUSION

Safflor yellow played an important role on blood stasis of rats.

In-vitro metabolism of celecoxib, a cyclooxygenase-2 inhibitor, by allelic variant forms of human liver microsomal cytochrome P450 2C9: correlation with CYP2C9 genotype and in-vivo pharmacokinetics

In-vitro studies were conducted to assess the impact of CYP2C9 genotype on the metabolism (methyl hydroxylation) and pharmacokinetics of celecoxib, a novel cyclooxygenase-2 inhibitor and CYP2C9 substrate. When compared to cDNA-expressed wild-type CYP2C9 (CYP2C9*1), the Vmax/Km ratio for celecoxib methyl hydroxylation was reduced by 34% and 90% in the presence of recombinant CYP2C9*2 and CYP2C9*3, respectively. These data indicated that the amino acid substitution at position 359 (Ile to Leu) elicited a more pronounced effect on the metabolism of celecoxib than did a substitution at position 144 (Arg to Cys). The Vmax/Km ratio was also decreased in microsomes of livers genotyped CYP2C9*1/*2 (47% decrease, mean of two livers), or CYP2C9*1/*3 (59% decrease, one liver). In all cases, these changes were largely reflective of a decrease in Vmax, with a minimal change in Km. Based on simulations of the in-vitro data obtained with the recombinant CYP2C9 proteins, it was anticipated that the pharmacokinetics of celecoxib (as a much as a five-fold increase in plasma AUC) would be altered (versus CYP2C9*1/*1 subjects) in subjects genotyped heterozygous or homozygous for the CYP2C9*2 (Cys144) or CYP2C9*3 (Leu359) allele. In a subsequent clinical study, the AUC of celecoxib was increased (versus CYP2C9*1/*1 subjects) approximately 2.2-fold (range, 1.6-3-fold) in two CYP2C9*1/*3 subjects and one CYP2C9*3/*3 subject receiving a single oral dose (200 mg) of the drug. In contrast, there was no significant change in celecoxib AUC in two subjects genotyped CYP2C9*1/*2.

Substrate inhibition kinetics for cytochrome P450-catalyzed reactions

Most cytochrome P450 (P450 or CYP)-catalyzed reactions are adequately described by classical Michaelis-Menten kinetic parameters (e.g., Km and Vmax), which are usually determined by a saturation profile of velocity of product formation versus substrate concentration. In turn, these parameters may be used to predict pharmacokinetics. However, some P450 enzymes exhibit atypical or non-Michaelis-Menten kinetics, due largely to substrate inhibition at higher concentrations of substrate. Although the mechanism of substrate inhibition is unknown, ignoring it and truncating the data can lead to erroneous estimates of kinetic parameters. In the present study, 13 P450 marker substrates were examined with 10 recombinant P450 proteins, and 6 were found, to varying degrees, to exhibit substrate inhibition. To understand the nature of the inhibition, a kinetic model was proposed (assuming that two binding sites exist on the enzyme) and used to fit the experimental data. The derived data indicated that 1) the K(I) values (substrate inhibition) were approximately 1.2- to 10-fold greater than the respective K(S) values; 2) both K(S) and K(I) values may be affected by the interaction of the two bound substrates within the enzyme, exhibited by a factor alpha (alpha = 5.1-23.3); and 3) enzyme activity was inhibited markedly (39-97%) at excess concentrations of the substrates (beta = 0.03-0.61). These findings suggest that substrates have access to both the inhibitory site and catalytic site simultaneously (K(I) > K(S)). Furthermore, the two sites, in the presence of substrate, can interact with each other. Therefore, the degree of inhibition of the enzyme is dependent on the concentration of the substrate (usually >K(I)) that sufficiently occupies the inhibitory site.

Enzyme kinetics of cytochrome P450-mediated reactions

The most common drug-drug interactions may be understood in terms of alterations of metabolism, associated primarily with changes in the activity of cytochrome P450 (CYP) enzymes. Kinetic parameters such as Km, Vmax, Ki and Ka, which describe metabolism-based drug interactions, are usually determined by appropriate kinetic models and may be used to predict the pharmacokinetic consequences of exposure to one or multiple drugs. According to classic Michaelis-Menten (M-M) kinetics, one binding site models can be employed to simply interpret inhibition (pure competitive, non-competitive and uncompetitive) or activation of the enzyme. However, some cytochromes P450, in particular CYP3A4, exhibit unusual kinetic characteristics. In this instance, the changes in apparent kinetic constants in the presence of inhibitor or activator or second substrate do not obey the rules of M-M kinetics, and the resulting kinetics are not straightforward and hamper mechanistic interpretation of the interaction in question. These unusual kinetics include substrate activation (autoactivation), substrate inhibition, partial inhibition, activation, differential kinetics and others. To address this problem, several kinetic models can be proposed, based upon the assumption that multiple substrate binding sites exist at the active site of a particular P450, and the resulting kinetic constants are, therefore, solved to adequately describe the observed interaction between multiple drugs. The following is an overview of some cytochrome P450-mediated classic and atypical enzyme kinetics, and the associated kinetic models. Applications of these kinetic models can provide some new insights into the mechanism of P450-mediated drug-drug interactions.

The tkNeo gene, but not the pgkPuro gene, can influence the ability of the beta-globin LCR to enhance and confer position-independent expression onto the beta-globin gene

Whether drug-selectable genes can influence expression of the beta-globin gene linked to its LCR was assessed here. With the tkNeo gene placed in cis and used to select transfected cells, the beta-globin gene was expressed fourfold lower when it was positioned upstream of the LCR rather than downstream. This difference did not occur when the pgkPuro gene replaced tkNeo. Moreover, the beta-globin gene situated upstream of the LCR was transcribed without position effects when it was cotransfected with a pgkPuro-containing plasmid, whereas cotransfection with a tkNeo plasmid gave measurable position effects. Previous results from transfected cells selected via a linked tkNeo gene suggested that the 3' end of the beta-globin gene has no impact on LCR-enhanced expression. Here, removal of the 3' end of the beta-globin gene resulted in lower and much more variable expression in both transgenic mice and cells cotransfected with pgkPuro. Together, the results suggest that tkNeo, but not pgkPuro, can strongly influence expression of the beta-globin gene linked to its LCR. The findings could partly explain why data on beta-globin gene regulation obtained from transfected cells have often not agreed with those obtained using transgenic mice. Hence, one must be careful in choosing a drug-selectable gene for cell transfection studies.

Local downregulation of enterochromaffin-like cell histamine formation in ulcer healing: a study in rats

BACKGROUND AND AIMS

Although enterochromaffin-like (ECL) cells are the major source of histamine for the regulation of gastric acid secretion, their role in ulcer healing has not been fully investigated. The present study aimed to investigate changes in ECL cell components as well as markers for somatostatin cells, parietal cells and macrophages during the healing of experimental ulcers in rats.

METHODS

Standardised ulcer was induced directly in the rat gastric mucosa by brief application of acetic acid. At different time intervals following ulcer induction (1-15 days), histamine, histidine decarboxylase (HDC), chromogranin A, pancreastatin, vesicular monoamine transporter 2 (VMAT-2), H-K-ATPase, somatostatin as well as ED1 and ED2 (macrophage markers) were localised by immunocytochemistry. ED1- and histamine-immunoreactive cells were counted at different time points. HDC- and VMAT-2-immunoreactive cells were demonstrated by double staining and counted. The mRNA of HDC, chromogranin A and somatostatin was demonstrated by in situ hybridisation and quantitated by computerised image analysis.

RESULTS

HDC immunoreactivity and mRNA were markedly reduced in the ECL cells at the ulcer margin from day 1 following ulcer induction and onwards; after day 5 HDC immunoreactivity and mRNA rose gradually and had almost normalised by day 15. This local and transient downregulation of HDC was accompanied by a similar decrease in ECL cell histamine. In contrast to HDC and histamine, other ECL cell components (chromogranin A, pancreastatin, VMAT-2) as well as somatostatin and H-K ATPase were still demonstrable at the ulcer margin and displayed no major changes at any time point studied. Of the macrophage markers, ED1, but not ED2, could be identified at the ulcer margin, and the number of ED1-immunoreactive cells was high in the ulcer margin from day 1 to day 5 after ulcer induction. The increase in ED1-positive cells and the decrease in HDC-expressing cells were coincident in time and localisation.

CONCLUSION

The present results revealed a local and transient downregulation of HDC in the ECL cells at the ulcer margin. This may account for the decrease in ECL cell histamine observed. The local infiltration of macrophages into the ulcer margin suggests that inflammatory mediators are involved in the local suppression of ECL cell activity during ulcer healing.

Major role of human liver microsomal cytochrome P450 2C9 (CYP2C9) in the oxidative metabolism of celecoxib, a novel cyclooxygenase-II inhibitor

In vitro studies were conducted to identify the cytochromes P450 (CYP) involved in the oxidative metabolism of celecoxib. The hydroxylation of celecoxib conformed to monophasic Michaelis-Menten kinetics (mean +/- S.D., n = 4 livers, K(m) = 3.8 +/- 0.95 microM, V(max) = 0.70 +/- 0.45 nmol/min/mg protein) in the presence of human liver microsomes, although substrate inhibition was significant at higher celecoxib concentrations. The treatment of a panel of human liver microsomal samples (n = 16 subjects) with antibodies against CYP2C9 and CYP3A4 inhibited the formation of hydroxy celecoxib by 72 to 92% and 0 to 27%, respectively. The presence of both antibodies in the incubation suppressed the activity by 90 to 94%. In addition, the formation of hydroxy celecoxib significantly correlated with CYP2C9-selective tolbutamide methyl hydroxylation (r = 0.92, P <. 001) and CYP3A-selective testosterone 6beta-hydroxylation (r = 0.55, P <.02). In contrast, correlation with activities selective for other forms of CYP was weak (r </= 0.46). Chemical inhibition studies showed that ketoconazole (selective for CYP3A4) and sulfaphenazole (selective for CYP2C9) inhibited the formation of hydroxy celecoxib in a concentration-dependent manner, whereas potent inhibitors selective for other forms of CYP did not show any significant effect over a range of 1 to 10 microM. In agreement, cDNA-expressed CYP2C9 catalyzed the formation of hydroxy celecoxib with an apparent K(m) value (microM) and a V(max) value (pmol/min/pmol recombinant CYP) of 5.9 and 21.7, whereas a higher K(m) value (18.2) and a lower V(max) value (1.42) were obtained with rCYP3A4. It is concluded that methyl hydroxylation of celecoxib is primarily catalyzed by human liver microsomal CYP2C9, although CYP3A4 also plays a role.

Innervation of the gastric mucosa

A plethora of neuronal messengers ("classical" transmitters, gaseous messengers, amino acid transmitters, and neuropeptides) are capable of mediating or modulating gastric functions. Accordingly, the stomach is richly innervated. Gastric nerves are either intrinsic to the gastric wall, i.e., they have their cell bodies in the intramural ganglia and thus belong to the enteric nervous system, or they reach the stomach from outside, originating in the brainstem, in sympathetic ganglia, or in sensory ganglia. Topographically, the nerve fibers in the stomach reach all layers from the most superficial portions of the gastric glands to the outer smooth muscle layer. This wide distribution implies that virtually all different cell types may be reached by neuronal messengers. Within the gastric mucosa endocrine and paracrine cells (e.g., gastrin cells, ECL cells, somatostatin cells), exocrine cells (parietal cells, chief cells, mucous cells), smooth muscle cells, and stromal cells are regulated by neuronal messengers. The sensory innervation, responding to capsaicin, plays an important role in mucosal protection, and in ulcer healing. Presumably also other nerves are involved and a plasticity in the neuropeptide expression has been demonstrated at the margin of gastric ulcers. Taken together, available data indicate a complex interplay between hormones, paracrine messengers and neuronal messengers, growth factors and cytokines in the regulation of gastric mucosal activities such as secretion, local blood flow, growth, and restitution after damage.

Innervation of the gastric mucosa

A plethora of neuronal messengers ("classical" transmitters, gaseous messengers, amino acid transmitters, and neuropeptides) are capable of mediating or modulating gastric functions. Accordingly, the stomach is richly innervated. Gastric nerves are either intrinsic to the gastric wall, i.e., they have their cell bodies in the intramural ganglia and thus belong to the enteric nervous system, or they reach the stomach from outside, originating in the brainstem, in sympathetic ganglia, or in sensory ganglia. Topographically, the nerve fibers in the stomach reach all layers from the most superficial portions of the gastric glands to the outer smooth muscle layer. This wide distribution implies that virtually all different cell types may be reached by neuronal messengers. Within the gastric mucosa endocrine and paracrine cells (e.g., gastrin cells, ECL cells, somatostatin cells), exocrine cells (parietal cells, chief cells, mucous cells), smooth muscle cells, and stromal cells are regulated by neuronal messengers. The sensory innervation, responding to capsaicin, plays an important role in mucosal protection, and in ulcer healing. Presumably also other nerves are involved and a plasticity in the neuropeptide expression has been demonstrated at the margin of gastric ulcers. Taken together, available data indicate a complex interplay between hormones, paracrine messengers and neuronal messengers, growth factors and cytokines in the regulation of gastric mucosal activities such as secretion, local blood flow, growth, and restitution after damage.

Percutaneous implantation of a Port-Catheter System using the left subclavian artery

PURPOSE

To evaluate the safety and feasibility of a percutaneous Port-Catheter System (PCS) implanted via the subclavian artery (SCA) for regional chemotherapy or chemoembolization of thoracic, abdominal, and pelvic malignant tumors.

METHODS

Percutaneous puncture of the SCA was performed in 256 patients with thoracic, abdominal, or pelvic malignant tumors; then a catheter was inserted into the target artery. After the first transcatheter chemotherapy or chemoembolization with an emulsion of lipiodol and anticancer agents, an indwelling catheter was introduced with its tip placed in the target artery and its end subcutaneously connected to a port.

RESULTS

The procedure was successfully completed in all 256 cases (100%). The indwelling catheter tip was satisfactorily placed in the target arteries in 242 cases (98%). Complications attributable to the procedure occurred in 20 (7.8%) cases, including pneumothorax (n = 10, 4%), hemothorax (n = 1, 0.4%), infections in the pocket (n = 4, 1.6%), and hematoma at the puncture site (n = 5, 2%). There were no severe sequelae or deaths. The duration of PCS usage was 1-36 months (median 9.5 months). During the course of treatment, occlusion of the target artery occurred in 20 cases (7.8%). Dislocation of the tip of the indwelling catheter occurred in 12 cases (4.7%); in 10 of the 12, the tip of the indwelling catheter was repositioned into the target artery. In all 10 cases no large symptomatic hematomas developed after the PCS was removed.

CONCLUSION

Percutaneous PCS implantation via the left SCA, a relatively new procedure, is a safe and less invasive treatment approach than surgical placement for malignancies.

Role of a potent inhibitory monoclonal antibody to cytochrome P-450 3A4 in assessment of human drug metabolism

Cytochrome P-450 (CYP) 3A4 is an inordinately important CYP enzyme that catalyzes the metabolism of a vast array of clinically used drugs. Microsomal proteins of Spodoptera frugiperda (Sf21) insect cells infected with recombinant baculoviruses encoding CYP3A4 cDNA were used to immunize mice and to develop a monoclonal antibody (mAb(3A4a)) specific to CYP3A4 through the use of hybridoma technology. The mAb is both a potent inhibitor and a strong binder of CYP3A4. One and 5 microl (0.5 and 2.5 microM IgG(2a)) of the mAb mouse ascites in 1-ml incubation containing 20 pmol of CYP3A4 strongly inhibited the testosterone 6beta-hydroxylation by 95 and 99%, respectively, and, to a lesser extent, cross-inhibited CYP3A5 and CYP3A7 activity. mAb(3A4a) exhibited no cross-reactivity with any of the other recombinant human CYP isoforms (CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP2E1) in the course of CYP reaction phenotyping and Western immunoblot analyses. The potency of mAb-induced inhibition is insensitive to substrate concentration in human liver microsomes. Therefore, mAb(3A4a) was used to assess the quantitative role of CYP3A4/5 to the metabolism of testosterone and diazepam in five human liver microsomes. The results showed that CYP3A4 and CYP3A5 contribute >95% to both testosterone 6beta-hydroxylation and diazepam 3-hydroxylation and 52 to 73% to diazepam N-demethylation, respectively. In addition, mAb(3A4a) significantly inhibited testosterone 6beta-hydroxylase activity in rhesus monkey liver microsomes to a degree equal to that observed with CYP3A4 in human liver microsomes. By comparison, no inhibition of testosterone 6beta-hydroxylase activity was observed in the presence of dog, rat, and mouse liver microsomes. The selectivity of ketoconazole, a chemical inhibitor of CYP3A4, was probed with mAb(3A4a) and was shown to be highly concentration dependent in the diazepam N-demethylation by human liver microsomes. The results demonstrate that inhibitory and immunoblotting mAb(3A4a) can offer a precise and useful tool for quantitative identification of CYP3A4/5 in the metabolism of drugs in clinical use and drugs in development.

Sigmoidal kinetic model for two co-operative substrate-binding sites in a cytochrome P450 3A4 active site: an example of the metabolism of diazepam and its derivatives

Cytochrome P450 3A4 (CYP3A4) plays a prominent role in the metabolism of a vast array of drugs and xenobiotics and exhibits broad substrate specificities. Most cytochrome P450-mediated reactions follow simple Michaelis-Menten kinetics. These parameters are widely accepted to predict pharmacokinetic and pharmacodynamic consequences in vivo caused by exposure to one or multiple drugs. However, CYP3A4 in many cases exhibits allosteric (sigmoidal) characteristics that make the Michaelis constants difficult to estimate. In the present study, diazepam, temazepam and nordiazepam were employed as substrates of CYP3A4 to propose a kinetic model. The model hypothesized that CYP3A4 contains two substrate-binding sites in a single active site that are both distinct and co-operative, and the resulting velocity equation had a good fit with the sigmoidal kinetic observations. Therefore, four pairs of the kinetic estimates (KS1, kalpha, KS2, kbeta, KS3, kdelta, KS4 and kgamma) were resolved to interpret the features of binding affinity and catalytic ability of CYP3A4. Dissociation constants KS1 and KS2 for two single-substrate-bound enzyme molecules (SE and ES) were 3-50-fold greater than KS3 and KS4 for a two-substrate-bound enzyme (SES), while respective rate constants kdelta and kgamma were 3-218-fold greater than kalpha and kbeta, implying that access and binding of the first molecule to either site in an active pocket of CYP3A4 can enhance the binding affinity and reaction rate of the vacant site for the second substrate. Thus our results provide some new insights into the co-operative binding of two substrates in the inner portions of an allosteric CYP3A4 active site.