Biomedical subjects
Publications and source records attributed to K M Lin.
Pharmacogenetics as a field of research is increasing the basis of knowledge on the use of psychotropics in different ethnic patient populations. This chapter summarizes current knowledge on the metabolism of anxiolytic agents with emphasis on pharmacogenetics and ethnic variations in drug responses.
The enzyme myeloperoxidase (MPO) is synthesized only in myeloid and monocytic cells, making it an important marker of the myeloid lineage. Transcription of the MPO gene is turned on early during the myeloblast stage of myeloid differentiation and is turned off when myeloid precursors are induced to differentiate along any one of a number of pathways. MPO transcripts show heterogeneity in size and sequence due, in part, to differential RNA splicing. We recently reported transfection studies which showed the presence of three distinct MPO promoters in the 5'-flanking region of the human MPO gene, suggesting that MPO transcription may also be regulated through the use of multiple promoters. We now report results of primer extension and RT-PCR experiments designed to determine if transcription of the human MPO gene is initiated at multiple promoter sites in vivo. MPO RNA obtained from myeloid cell lines was analyzed by primer extension using primers located at various sites between bp -1100 and bp +120 of the MPO gene. In addition, RT-PCR experiments were carried out using primer pairs located at intervals between bp -1000 and bp +2500 of the MPO gene. MPO transcripts were found to be initiated at three sites located about bp -920, bp -310, and bp +1 of the MPO gene, corresponding closely to our previously described P3, P2 and P1 promoters, respectively. Transcription initiated at the P1 site gave rise to large transcripts and showed the expected downregulation following induction of differentiation. On the other hand, transcripts initiated at the P3 and P2 sites did not show downregulation following induction of macrophage differentiation by TPA, and most did not appear to extend into the MPO coding region. Northern blot analysis of transcripts initiated at the P3 and P2 sites suggested that transcription at these sites was non-tissue-specific and indicated that many of these transcripts undergo premature termination. These results demonstrate that the MPO gene is transcribed in vivo primarily using the P1 promoter and that the low level of transcription occurring at the P2 and P3 sites is nonspecific and does not contribute significantly to physiologic regulation of MPO gene expression.
Both the beta-catenin and the nuclear factor kappaB (NF-kappaB) proteins are important regulators of gene expression and cellular proliferation. Two kinases, IKKalpha and IKKbeta, are critical activators of the NF-kappaB pathway. Here we present evidence that these kinases are also important in the regulation of beta-catenin function. IKKalpha- and IKKbeta-deficient mouse embryo fibroblasts exhibited different patterns of beta-catenin cellular localization. IKKbeta decreases beta-catenin-dependent transcriptional activation, while IKKalpha increases beta-catenin-dependent transcriptional activity. IKKalpha and IKKbeta interact with and phosphorylate beta-catenin using both in vitro and in vivo assays. Our results suggest that differential interactions of beta-catenin with IKKalpha and IKKbeta may in part be responsible for regulating beta-catenin protein levels and cellular localization and integrating signaling events between the NF-kappaB and Wingless pathways.
BACKGROUND: The mitochondrial heat-shock proteins HSP60 and HSP10 form a mitochondrial chaperonin complex, and previous studies have shown that their increased expression exerts a protective effect against ischemic injury when cardiac myocytes are submitted to simulated ischemia. The more detailed mechanisms by which such a protective effect occurs are currently unclear. We wanted to determine whether HSP60 and HSP10 could exert a protection against simulated ischemia and reoxygenation (SI/RO)-induced apoptotic cell death and whether such protection results from decreased mitochondrial cytochrome c release and caspase-3 activation and from the preservation of ATP levels by preservation of the electron transport chain complexes. In addition, we explored whether increased expression of HSP60 or HSP10 by itself exerts a protective effect. METHODS AND RESULTS: We overexpressed HSP60 and HSP10 together or separately in rat neonatal cardiac myocytes using an adenoviral vector and then subjected the myocytes to SI/RO. Cell death and apoptosis in myocytes were quantified by parameters such as enzyme release, DNA fragmentation, and caspase-3 activation. Overexpression of the combination of HSP60 and HSP10 and of HSP60 or HSP10 individually protected myocytes against apoptosis. This protection is accompanied by decreases in mitochondrial cytochrome c release and in caspase-3 activity and increases in ATP recovery and activities of complex III and IV in mitochondria after SI/RO. CONCLUSIONS: These results suggest that mitochondrial chaperonins HSP60 and HSP10 in combination or individually play an important role in maintaining mitochondrial integrity and capacity for ATP generation, which are the crucial factors in determining survival of cardiac myocytes undergoing ischemia/reperfusion injury.
RATIONALE: Ethnicity can affect the pharmacokinetics and pharmacodynamics of psychopharmacologic drugs. OBJECTIVES: Reboxetine disposition differences among Asians, blacks, and Caucasians were examined. METHODS: Healthy subjects (12 Asians, 12 blacks, 12 Caucasians) received a single oral dose of one 4-mg reboxetine tablet in an open label, parallel study design. Plasma concentrations of reboxetine enantiomers [R,R(-) reboxetine and predominantly active S,S(+) reboxetine] were quantified using HPLC-MS-MS. Plasma unbound fractions of reboxetine enantiomers were evaluated by equilibrium dialysis. Ethnic group effects on pharmacokinetic parameters were assessed by ANOVA. RESULTS: Mean S,S(+) reboxetine CLPO for blacks was significantly greater, compared to Asians and Caucasians (154+/-82 ml/min, 101+/-19 ml/min and 101+/-18 ml/min, respectively). Mean S,S(+) reboxetine free fractions (fu) were significantly greater for Asians and blacks, compared to Caucasians (3.04+/-1.28%, 2.89+/-0.69%, and 1.99+/-0.58%, respectively). S,S(+) Reboxetine unbound clearance (CLu) was significantly less for Asians, compared to blacks and Caucasians (3742+/-1468 ml/min, 5187+/-2027 ml/min, and 5294+/-1163 ml/min, respectively). S,S(+) Reboxetine mean unbound AUC (AUCu) in these groups were 20.2+/-7.1 ng.h/ml, 14.6+/-5.1 ng.h/ml, and 13.2+/-3.2 ng.h/ml, respectively. AUCu was significantly greater for Asians. CLu and AUCu did not differ significantly between blacks and Caucasians. Ethnic effects of R,R(-) reboxetine were similar to those observed for S,S(+) reboxetine. CONCLUSIONS: The AUCu difference between Asian and black and Caucasian subjects was modest. Tolerability differences among groups were not observed. No dosage adjustment is necessary for Asians or blacks.
In this brief review the authors strive to provide a broad overview of various factors that impinge on psychopharmacotherapeutic practices. The literature revealed an impressive progress in research focusing on the delineation of the biologic mechanisms responsible for cross-ethnic variations in psychotropic metabolism and effects. With the field progressing at an accelerating pace, there is little doubt that in the coming decade clinicians will be provided with a detailed map showing the prevalence and distribution of genetic polymorphisms of most, if not all, of the drug-metabolizing enzymes, and clinicians also will have an overall picture on what these polymorphisms mean clinically. At the same time, clinicians should also start to have a good grasp on the meaning of the variations of the genes that encode therapeutic targets of psychotropics (e.g., neurotransmitter transporters and receptors). Such genetic fingerprinting, which will soon become a clinical reality, will provide tremendous help in ensuring that pharmacotherapies are increasingly more individually tailored, taking into consideration each patients genetic makeups that vary substantially across ethnic groups. As exciting as these new developments will be, they are dwarfed by the challenges ahead on the cultural side of the equation. Issues that are still awaiting further clarification include the following: How do we assess patients' beliefs and expectations related to psychotropic treatment? How do we minimize the communication gaps between patients and clinicians who are often from divergent sociocultural backgrounds? To what extent, and in what ways, do cultural (environmental) factors interact with biologic factors, and what might be the most efficient way to systematically assess such interactions? Data that have emerged in the past several decades clearly indicate the importance of culture and ethnicity in influencing patients' psychopharmacological response. It is expected that continuing progress in the near future will bring a better understanding on the way these cultural and biologic processes, separately and in interaction with each other, mediate treatment responses. Such knowledge will be crucial for the optimal pharmacotherapeutic care of for the majority of patients who will increasingly be of diverse ethnic and cultural backgrounds and will represent a significant contribution to the field of psychopharmacology as a whole.
Factors which regulate transcription in immature myeloid cells are of great current interest for the light they may shed upon myeloid differentiation. In the course of screening for transcription factors which interact with the human myeloperoxidase (MPO) promoter we, for the first time, identified and cloned the cDNA and genomic DNA for human HBP1 (HMG-Box containing protein 1), a member of the high mobility group of non-histone chromosomal proteins. HBP1 cDNA was initially cloned from rat brain in 1994, but its presence in human cells or in myeloid tissue had not been described previously. The sequence of human HBP1 cDNA shows 84% overall homology with the rat HBP1 cDNA sequence. We have subsequently cloned the gene, which is present as a single copy, 25 kbp in length. Northern blotting reveals a single 2.6 kb mRNA transcript which is expressed at higher levels in human myeloid and B lymphoid cell lines than in T cell lines tested and is present in several non-myeloid human cell lines. Comparison of the mRNA and genomic sequences reveals the gene to contain 10 exons and 9 introns. The sequence of human HBP1 mRNA contains a single open reading frame, which codes for a protein 514 amino acids in length. The amino acid sequence specified by the coding region shows 95% homology with the rat HBP1 protein. The human protein sequence exhibits a putative DNA-binding domain similar to that seen in rat HBP1 and shows homology with the activation and repressor domains previously demonstrated in the rat protein. We have expressed human HBP1 protein both in vitro and in prokaryotic and eukaryotic cells. The expressed fusion protein binds to a sequence in a functionally important region within the basal human MPO promoter. In transient co-transfection experiments HBP1 enhances MPO promoter activity. Human HBP1 appears to be a novel transcription factor which is likely to play an important role in regulating transcription in developing myeloid cells.
BACKGROUND: Pharmacogenetic data are largely unavailable for Mexican Americans, despite being one of the largest populations in America. METHODS: The CYP2D6 genotype (n = 349) and dextromethorphan hydroxylation phenotype (n = 285) were studied in 380 Mexican American subjects from Los Angeles County. RESULTS: The allelic frequency was 22.8% for CYP2D6*2, 10.3% for CYP2D6*4, 7.4% for CYP2D6*10, 2.3% for CYP2D6*5, 1% for CYP2D6*XN (duplication), and <1% for CYP2D6*3 and CYP2D6*17. By using the published antimode for Caucasians, we identified nine subjects as poor metabolizers, an incidence of 3.2%. Of the eight poor metabolizers who were also genotyped, five either were homozygous for the CYP2D6*4 allele (4 cases) or had a combination of CYP2D6*4 and CYP2D6*5 alleles. The mean log(10) dextromethorphan/dextrorphan ratio was -2.47 for those classified as extensive metabolizers. The number of functional alleles among the extensive metabolizers correlated strongly with the phenotype, suggesting a gene-dose effect. CONCLUSION: Compared with previous reports on Caucasian populations, studies show that Mexican Americans appear to possess a lower rate of CYP2D6*4. Frequencies for the other alleles appear to be less divergent between the two groups. This genotypic pattern might be responsible for the lower rate for the poor metabolizer status, as well as for the faster enzyme activity in the extensive metabolizer subjects that was also reflected in our data.
Despite its importance in drug metabolism and disease susceptibility, CYP2D6 activity and genetic polymorphism have rarely been investigated in African-American populations. In order to bridge this gap, we examined the genotype and phenotype of the enzyme in 154 African-American (AA) and 143 Caucasian (C) normal volunteers. AAs are significantly more likely to possess *17 and *5, but less likely to have *4. Overall, the two groups were similar in their CYP2D6 activity as measured with dextromethorphan as the probe (metabolic ratio 2.21 +/- 0.78 for AAs; 2.11 +/- 0.86 for Cs; t = 1.02, NS). Two of four AAs and six of seven Cs were classified as poor metabolizers and have two nonfunctioning alleles. CYP2D6 activity is determined by *17, *4, *5 and age in AAs (r2 = 0.33, f = 18.8, P < 0.001) and by *4 and *XN in Cs (r2 = 0.14, f = 10.8, P < 0.001). These results support previous findings demonstrating the importance of *17 in determining CYP2D6 activity in AAs.
A growing number of studies clearly indicate the importance of race and ethnicity in the psychopharmacologic management of depression and anxiety disorders. The data highlight important pharmacokinetic, pharmacodynamic, and pharmacogenetic ethnic differences that may have profound implications for the efficacy and safety of psychotropic therapies. General treatment considerations based on these differences include greater attention to adverse event profiles, the possibility of improved clinical response at any given dose, and the potential need for lower starting doses and slower increases in dosage. Continued research in this area is clinically important as patients with increasingly divergent ethnic and cultural backgrounds seek treatment for a range of depressive and anxiety disorders.
OBJECTIVE: To provide primary care physicians with a better understanding of transcultural issues in depression and anxiety. PARTICIPANTS: The 4 members of the International Consensus Group on Depression and Anxiety were James C. Ballenger (chair), Jonathan R. T. Davidson, Yves Lecrubier, and David J. Nutt. Five faculty invited by the chair also participated: Laurence J. Kirmayer, Jean-Pierre Lepine, Keh-Ming Lin, Osamu Tajima, and Yutaka Ono. EVIDENCE: The consensus statement is based on the 5 review articles that are published in this supplement and the scientific literature relevant to the issues reviewed in these articles. CONSENSUS PROCESS: Group meetings were held over a 2-day period. On day 1, the group discussed the review articles, and the chair identified key issues for further debate. On day 2, the group discussed these issues to arrive at a consensus view. After the group meetings, the consensus statement was drafted by the chair and approved by all attendees. CONCLUSION: The consensus statement underlines the prevalence of depression and anxiety disorders across all cultures and nations while recognizing that cultural differences exist in symptom presentation and prevalence estimates. In all countries, the recognition of depression by clinicians in the primary care setting is low (generally less than 50%), and the consensus group recommends a 2-step process to aid the recognition and diagnosis of depression. In line with the low recognition of depression and anxiety disorders is the finding that only a small proportion of patients with depression or anxiety are receiving appropriate treatments for their condition. Biological diversity across ethnic groups may account for the differential sensitivity of some groups to psychotropic medication, but this area requires further investigation.
Gelsolin is activated by Ca(2+) to sever actin filaments. Ca(2+) regulation is conferred on the N-terminal half by the C-terminal half. This paper seeks to understand how Ca(2+) regulates gelsolin by testing the "tail helix latch hypothesis," which is based on the structural data showing that gelsolin has a C-terminal tail helix that contacts the N-terminal half in the absence of Ca(2+). Ca(2+) activation of gelsolin at 37 degrees C occurs in three steps, with apparent K(d) for Ca(2+) of 0.1, 0.3, and 6.4 x 10(-6) m. Tail helix truncation decreases the apparent Ca(2+) requirement for severing to 10(-7) m and eliminates the conformational change observed at 10(-6) m Ca(2+). The large decrease in Ca(2+) requirement for severing is not due to a change in Ca(2+) binding nor to Ca(2+)-independent activation of the C-terminal half per se. Thus, the tail helix latch is primarily responsible for transmitting micromolar Ca(2+) information from the gelsolin C-terminal half to the N-terminal half. Occupation of submicromolar Ca(2+)-binding sites primes gelsolin for severing, but gelsolin cannot sever because the tail latch is still engaged. Unlatching the tail helix by 10(-6) m Ca(2+) releases the final constraint to initiate the severing cascade.
Alzheimer's disease is as prevalent among Asian ethnic minority groups as among Caucasians. We explored Asian groups' utilization of available Alzheimer's disease services in California, using a uniquely large sample of Asian-Americans. The Minimum Uniform Dataset includes data from nine California Alzheimer's Disease Diagnostic and Treatment Centers. Of the 9,451 cases included in the Minimum Utilizable Dataset, 4.2% were Asian (primarily Chinese), 0.8% Filipino, 0.3% Pacific Islander, and 75.9% Caucasian. In comparison to their numbers within the nine California countries served, Asian ethnic elders were underrepresented in enrollment by approximately 50%, except at one center where all staff were bilingual. The centers referred a significantly greater proportion of Asian than Caucasian patients for financial help (47.8 vs. 7.4%, P < 0.001), case management (47.8 vs. 22.3%, P < 0.001), and to Alzheimer's disease day care (41.3 vs. 28.4%, P < 0.05). A significantly greater proportion of Asian caregivers received referrals to caregiver resource centers (32.6 vs. 61.3%, P < 0.001) and financial help (29.6 vs. 4.7%, P < 0.001). A smaller proportion of Asian patients received referrals to home health services than Caucasians (4.3 vs. 14.9%, P < 0.05). Filipino patients were also referred more frequently to financial assistance than Caucasians (P < 0.05). Asians and Pacific Islanders under-enroll at centers specializing in AD care. Bilingual staff at centers specializing in dementia care, training for community physicians who treat these patients, and establishment of caregiver support groups within Asian and Pacific Islander communities may enhance the enrollment of these elders. AD care centers in areas supporting Asian and Filipino families may need to concentrate resources on providing financial assistance in case management.
In this study we investigated inhibition of Arylamine N-acetyltransferase (NAT) activity in rat blood and liver tissue cytosols by luteolin. Using high-performance liquid chromatography, NAT activity for acetylation of 2-aminofluorene and remaining unacetylated 2-aminofluorene were examined. The NAT activity in rat blood and liver tissue was inhibited by luteolin in a dose-dependent manner: higher concentrations of luteolin in the reaction resulted in greater inhibition of NAT activities in both examined tissues. The data also indicated that luteolin decreased apparent Km and Vmax of NAT enzymes from rat blood and liver tissue cytosols. This report is the first demonstration that luteolin can affect rat blood and liver tissue NAT activity.
The conventional and accepted treatment for curative resection of colon cancer is laparotomy with hemicolectomy for right or left sided lesions. The technique of colon resection through an open laparotomy incision is well known. Over the past several years, laparoscopically assisted colectomy has been developed and studied, following the explosion of laparoscopic technology from the cholecystectomy experience and with acquisition of advanced general laparoscopic techniques. The right, left or sigmoid colon can be mobilized and regional lymphadenectomy performed using laparoscopic instruments and video-imaging equipment. The advantage of laparoscopic colectomy is the use of small abdominal port site and wound incisions which translate to reduced postoperative pain and analgesic requirement, earlier return of bowel function and normal physical activities, and shorter hospital stay without increasing health care costs. Laparoscopic colectomy compares favorably with open colectomy in terms of surgical morbidity and mortality. The laparoscopic approach has been shown to be technically and oncologically feasible with equivalent lymph node harvest from mesenteric lymphadenectomy and achieves adequate proximal and distal margins of colonic resection. Despite initial early anecdotal reports of port site cancer recurrence in laparoscopically assisted colectomy, port site recurrence is rare and its incidence is similar to incisional recurrences in conventional open colectomy. Recent prospective comparative studies have demonstrated equivalent patient survival and equivalent local or distant colon cancer recurrences for open versus laparoscopic curative resection of colon cancer.
Extant data, mostly from studies in vitro, suggest that coumarin and nicotine are both metabolized by CYP2A6, a cytochrome P450 isozyme. In order to investigate this issue further, the activity of this enzyme in vivo was measured in 37 non-smokers and 37 smokers using coumarin (2.0 mg, PO) as the metabolic probe. The percentage of coumarin metabolized to 7-hydroxycoumarin in 8 h was measured in urine by high-pressure liquid chromatography. There was more than 10-fold variability in coumarin metabolism in both groups. Coumarin metabolism was significantly reduced in smokers (46.6 +/- 4.4%) as compared to non-smokers (66.4 +/- 3.5%; p < or = .001). The results support previous in vitro findings that both coumarin and nicotine are metabolized, at least in part, by a common pathway, which most likely is CYP2A6.
The human liver tumour cell line (J5) was selected in order to evaluate whether or not luteolin affected arylamine N-acetyltransferase (NAT) activity. Using high performance liquid chromatography, the NAT activity for acetylation of arylamine substrates (2-aminofluorene and p-aminobenzoic acid) was determined. The cytosolic NAT activity in human liver tumour cells was 2.74+/-0.26 and 1.68+/-0.20 nmol/min/mg of protein for 2-aminofluorene and p-aminobenzoic acid, respectively. Luteolin displayed a dose-dependent inhibition to cytosolic NAT activity and intact human liver tumour cells. Time-course experiments showed that NAT activity measured from intact human liver tumour cells was inhibited by luteolin for up to 24 h. Using standard steady-state kinetic analysis, it was shown that luteolin was a possible noncompetitive inhibitor to NAT activity in cytosols. This report is the first to show how luteolin affects NAT activity in human liver tumour cells.
The influence of ethnicity on the manifestation of EEG sleep changes in depression was studied in 95 patients (21 African-Americans [AA], 17 Asians [AS], 37 Caucasians [C] and 20 Hispanics [H]) with unipolar major depression. Subjects were studied twice for 2 consecutive nights. On the second night of each 2-night session, placebo or scopolamine (1.5 microg/kg, IM, at 23.00 h) was administered. On the baseline (placebo) night, sleep architecture, sleep continuity and rapid eye movement (REM) sleep variables were generally comparable among the groups. However, REM sleep was less in AA and AS subjects than in C and H subjects. Furthermore, the distribution of REM sleep over the course of the night in AA and AS subjects differed significantly from that in the C and H groups. Although scopolamine significantly affected sleep continuity and REM sleep measures, no significant differential effects of scopolamine were observed. Because many antidepressants suppress REM sleep, the differences in baseline REM sleep observed might be related to the greater sensitivity of some ethnic-minority depressed patients to pharmacotherapy.