Pharmacist assessment of drug-gene interactions and drug-induced phenoconversion in major depressive disorder: a case report.

BACKGROUND: Response to antidepressant therapy is highly variable among individuals. Pharmacogenomic (PGx) testing presents an opportunity to guide drug selection while optimizing therapy outcomes and/or decreasing the risk for toxicity. CASE PRESENTATION: A patient with multiple comorbidities, including severe major depressive disorder (MDD), experienced adverse drug events and undesirable response to multiple antidepressant medications (i.e., bupropion, escitalopram, and venlafaxine). A clinical pharmacist assessed significant drug-gene, drug-drug, and drug-drug-gene interactions as well as other clinical factors to provide recommendations for antidepressant therapy optimization. CONCLUSION: This case highlights the importance of PGx testing and the key role of pharmacists in identifying and mitigating drug-related problems and optimizing drug therapy in patients with MDD.

exo1-Dependent mutator mutations: model system for studying functional interactions in mismatch repair.

EXO1 interacts with MSH2 and MLH1 and has been proposed to be a redundant exonuclease that functions in mismatch repair (MMR). To better understand the role of EXO1 in mismatch repair, a genetic screen was performed to identify mutations that increase the mutation rates caused by weak mutator mutations such as exo1Delta and pms1-A130V mutations. In a screen starting with an exo1 mutation, exo1-dependent mutator mutations were obtained in MLH1, PMS1, MSH2, MSH3, POL30 (PCNA), POL32, and RNR1, whereas starting with the weak pms1 allele pms1-A130V, pms1-dependent mutator mutations were identified in MLH1, MSH2, MSH3, MSH6, and EXO1. These mutations only cause weak MMR defects as single mutants but cause strong MMR defects when combined with each other. Most of the mutations obtained caused amino acid substitutions in MLH1 or PMS1, and these clustered in either the ATP-binding region or the MLH1-PMS1 interaction regions of these proteins. The mutations showed two other types of interactions: specific pairs of mutations showed unlinked noncomplementation in diploid strains, and the defect caused by pairs of mutations could be suppressed by high-copy-number expression of a third gene, an effect that showed allele and overexpressed gene specificity. These results support a model in which EXO1 plays a structural role in MMR and stabilizes multiprotein complexes containing a number of MMR proteins. A similar role is proposed for PCNA based on the data presented.

Sevelamer hydrochloride (Renagel), a phosphate-binding polymer, does not alter the pharmacokinetics of two commonly used antihypertensives in healthy volunteers.

Sevelamer hydrochloride (Renagel) is a nonabsorbed phosphate-binding polymer approved for the treatment of hyperphosphatemia in adult hemodialysis patients. The authors studied the potential effect of sevelamer on the pharmacokinetics of two antihypertensive drugs, enalapril (20 mg) and metoprolol (100 mg), commonly used in end-stage renal disease patients. Two studies were conducted. Both were single dose, crossover design with or without a 2.4 g dose of sevelamer in healthy volunteers. Within each study, there was a 7-day washout interval between the two dose administrations. There were 28 volunteers in the enalapril study and 32 in the metoprolol study. The mean plasma concentrations versus time profiles of enalapril, enalaprilat, and metoprolol were not altered by the simultaneous administration of sevelamer. Values for the ratio of ln[AUC(0-infinity)], ln[AUC(0-t)], and ln(Cmax] with and without sevelamer were approximately 100%, and the 90% confidence intervals for the ratios of these parameters with and without sevelamer were within the 80% to 125% range in all cases except for the ln[Cmax] of enalapril, which had an upper confidence bound of 125.4%. The authors conclude that sevelamer does not interfere with the absorption and elimination of enalapril and metoprolol.

Checkpoint-dependent activation of mutagenic repair in Saccharomyces cerevisiae pol3-01 mutants.

The Saccharomyces cerevisiae DNA polymerase delta proofreading exonuclease-defective mutation pol3-01 is known to cause high rates of accumulating mutations. The pol3-01 mutant was found to have abnormal cell cycle progression due to activation of the S phase checkpoint. Inactivation of the S phase checkpoint suppressed both the pol3-01 cell cycle progression defect and mutator phenotype, indicating that the pol3-01 mutator phenotype was dependent on the S phase damage checkpoint pathway. Epistasis analysis suggested that a portion of the pol3-01 mutator phenotype involves members of the RAD6 epistasis group that function in both error-free and error-prone repair. These results indicate that activation of a checkpoint in response to certain types of replicative defects can result in the accumulation of mutations.

Dominant mutations in three different subunits of replication factor C suppress replication defects in yeast PCNA mutants.

To identify proteins that interact with the yeast proliferating cell nuclear antigen (PCNA), we used a genetic approach to isolate mutations that compensate for the defects in cold-sensitive (Cs(-)) mutants of yeast PCNA (POL30). Because the cocrystal structure of human PCNA and a p21(WAF1/CIP1) peptide shows that the interdomain region of PCNA is a site of p21 interaction, we specifically looked for new mutations that suppress mutations in the equivalent region of yeast PCNA. In independent screens using three different Cs(-) mutants, we identified spontaneously arising dominant suppressor mutations in the RFC3 gene. In addition, dominant suppressor mutations were identified in the RFC1 and RFC2 genes using a single pol30 mutant. An intimate association between PCNA and RFC1p, RFC2p, and RFC3p is suggested by the allele-restricted suppression of 10 different pol30 alleles by the RFC suppressors. RFC1, RFC2, and RFC3 encode three of the five subunits of the replication factor C complex, which is required to load PCNA onto DNA in reconstituted DNA replication reactions. Genomic sequencing reveals a common region in RFC1p, RFC2p, and RFC3p that is important for the functional interaction with PCNA. Biochemical analysis of the wild type and mutant PCNA and RFC3 proteins shows that mutant RFC3p enhances the production of long DNA products in pol delta-dependent DNA synthesis, which is consistent with an increase in processivity.

Video-assisted thoracoscopy in the management of recurrent spontaneous pneumothorax in the pediatric population.

BACKGROUND AND OBJECTIVES: The purpose of the present study was to evaluate the application of video-assisted thoracoscopy in the management of recurrent spontaneous pneumothorax in the pediatric population. PATIENTS AND METHODS: Between 1995 and 1997, four patients with recurrent spontaneous pneumothorax were treated. Ages varied from 14 to 17 years. There were three males and one female. Two patients had spontaneous pneumothorax twice, and the other two had it three times. Three patients had primary spontaneous pneumothorax, and the fourth one had spontaneous pneumothorax secondary to cystic fibrosis. Computerized tomography of the chest demonstrated blebs in two patients, and in the other two it was suggestive of apical blebs but not definitive. All patients had failed treatment by tube thoracostomy. Video-assisted thoracoscopy demonstrated blebs in all patients. Removal was easily accomplished with an endoscopic automatic stapling device. The procedure was completed with mechanical pleurodesis, multiple intercostal blocks and intrapleural bupivacaine for control of pain. RESULTS: All patients had a quick and uneventful recovery. Follow-up ranged from one to three years. There were no complications or subsequent recurrences of the pneumothorax. CONCLUSIONS: Video-assisted thoracoscopy is a safe and effective technique in recurrent spontaneous pneumothorax. It allows for accurate identification and removal of the blebs, with quick recovery, minimal discomfort and good cosmetic results.

Identification of a human gene encoding a homologue of Saccharomyces cerevisiae EXO1, an exonuclease implicated in mismatch repair and recombination.

The EXO1 gene was identified in Saccharomyces cerevisiae as a gene encoding an exonuclease that interacts with MSH2 and functions in mismatch repair and genetic recombination. To understand the role of EXO1 in higher eukaryotes, we identified the human EXO1 gene. The hEXO1 predicted amino acid sequence shares 26.6% identity with the S. cerevisiae EXO1 amino acid sequence. The human and S. cerevisiae proteins showed a similar ability to complement the mutator phenotype of S. cerevisiae rad27 mutants indicating that the two proteins are functionally similar. There appear to be two forms of hEXO1 that differ by the COOH-terminal 1 and 44 amino acids, respectively, and these appear to result from alternative RNA splicing. The hEXO1 gene consists of 14 exons and is transcribed to yield a 3-kb mRNA. Radiation hybrid and fluorescence in situ hybridization mapping studies indicate that the human gene is located at 1q42.2-qter. Northern blot analysis demonstrates that hEXO1 is expressed in high levels in testis; elevated expression was also observed in thymus and colon and to a lesser extent in small intestine, placenta, spleen, and ovary.

Cytogenetic effects of copper-containing intrauterine contraceptive device (IUCD) on blood lymphocytes.

Forty women using the copper-containing intrauterine contraceptive device (IUCD) for various periods and 22 control women were studied. The copper and zinc levels were measured in the plasma of the IUCD users and the control group. Chromosomal analyses were performed on blood lymphocytes of the same groups. Results showed that plasma copper level was significantly higher in the IUCD users than in that of controls (1.25+/-0.14 microg/ml vs. 0.89+/-0.04 microg/ml, P<0. 05). A decline in plasma zinc level from 2.90+/-0.41 microg/ml to 1. 27+/-0.13 microg/ml, P<0.05, with a significant alteration in plasma copper/zinc ratio was also measured in the IUCD women (62% vs. 111%, P<0.05). Chromosomal aberrations (4.47+/-1.40 vs. 0.62+/-0.12/100 cell, P<0.01) and high frequencies of sister chromatid exchanges (8. 79+/-0.46 vs. 6.59+/-0.19 SCE/cell, P<0.01) were evident in the IUCD women especially in those using the IUCD for more than 24 months. The combination of high copper plasma level, chromosomal aberrations and the increased frequency of sister chromatid exchange may support the existence of a positive correlation between the long term use of the IUCDs and DNA damage in the host somatic cells.

Evidence for involvement of yeast proliferating cell nuclear antigen in DNA mismatch repair.

DNA mismatch repair plays a key role in the maintenance of genetic fidelity. Mutations in the human mismatch repair genes hMSH2, hMLH1, hPMS1, and hPMS2 are associated with hereditary nonpolyposis colorectal cancer. The proliferating cell nuclear antigen (PCNA) is essential for DNA replication, where it acts as a processivity factor. Here, we identify a point mutation, pol30-104, in the Saccharomyces cerevisiae POL30 gene encoding PCNA that increases the rate of instability of simple repetitive DNA sequences and raises the rate of spontaneous forward mutation. Epistasis analyses with mutations in mismatch repair genes MSH2, MLH1, and PMS1 suggest that the pol30-104 mutation impairs MSH2/MLH1/PMS1-dependent mismatch repair, consistent with the hypothesis that PCNA functions in mismatch repair. MSH2 functions in mismatch repair with either MSH3 or MSH6, and the MSH2-MSH3 and MSH2-MSH6 heterodimers have a role in the recognition of DNA mismatches. Consistent with the genetic data, we find specific interaction of PCNA with the MSH2-MSH3 heterodimer.

In vivo analysis reveals that the interdomain region of the yeast proliferating cell nuclear antigen is important for DNA replication and DNA repair.

To identify the regions of the proliferating cell nuclear antigen (PCNA) that are important for function in vivo, we used random mutagenesis to isolate 10 cold-sensitive (Cs-) and 31 methyl methanesulfonate-sensitive (Mmss) mutations of the PCNA gene (POL30) in Saccharomyces cerevisiae. Unlike the Mmss mutations, the Cs- mutations are strikingly clustered in the interdomain region of the three-dimensional PCNA monomer structure. At the restrictive temperature, the Cs- pol30 mutants undergo a RAD9-dependent arrest as large-budded cells with a 2c DNA content. Defects in DNA synthesis are suggested by a significant delay in the progression of synchronized pol30 cells through S phase at the restrictive temperature. DNA repair defects are revealed by the observation that Cs- pol30 mutants are very sensitive to the alkylating agent MMS and mildly sensitive to ultraviolet radiation, although they are not sensitive to gamma radiation. Finally, analysis of the chromosomal DNA in pol30 cells by velocity sedimentation gradients shows that pol30 cells accumulate single-stranded DNA breaks at the restrictive temperature. Thus, our results show that PCNA plays an essential role in both DNA replication and DNA repair in vivo.

Effect of copper-containing intrauterine contraceptive devices (IUCD) on growth of endometrial and cervical cells.

PIP: Physicians at the School of Medicine at the University of Baghdad in Iraq took a biopsy of endometrial and cervical tissue from women between 25-40 years old before and after using a copper IUD. Researchers exposed each tissue type to autoradiography using 5% methyl tritiated thymidine to indicate active cell metabolism. They also examined each type with an electron microscope. Thymidine uptake fell as duration of a copper IUD was used. For example, 52% of the endometrial and cervical cells were viable before insertion of the copper IUD. After 5 months, thymidine uptake fell remarkably to 32%. It fell to 20% at 12 months, 10% at 18 months, and 6% at 36 months. The thymidine uptake between endometrial and cervical tissue was not statistically different. The major change in the cervix as observed under electron microscopy included a few to a significant number of lymphocytes between the epithelial cells. Apical protrusions remained the same in the secretory cells of the endothelial lining in the endometrium and the glands. In tissues exposed to a copper IUD, the mitochondria of cells in the lumen and glands swelled and the number of lysosomes increased. Further, the number of lymphocytes also increased in both the cervix and endometrium. These results demonstrate the inhibition of mitotic activity in cervical and endometrial cells brought on by a copper IUD, especially during the 1st 2 months. This action could adversely affect a fetus if pregnancy occurs at this time. The researchers suggest that health practitioners advise any pregnant woman who had only recently got a copper IUD to abort the fetus.^ieng

Dietary fish oil supplements preserve renal function in renal transplant recipients with chronic vascular rejection.

The effect of dietary fish oil supplements on renal failure and lipid abnormalities was studied in 14 adult renal transplant recipients with chronic vascular rejection. The rate of decline of renal function (assessed by studying the slope of reciprocal plasma creatinine plots) slowed significantly during a 6-month period on fish oil supplements compared with the preceding 6-month control period (slope 1/cr during supplementation -3.6 X 10(-5) mumols/l per month compared with -13.5 X 10(-5) before, the difference in slope being -9.8 X 10(-5), 95% confidence interval (CI) -16.2 X 10(-5), -3.5 X 10(-5), P less than 0.05). Total plasma triglyceride concentrations decreased during supplementation (mean change -1.15 mmol/l, 95% CI -1.84, -0.47, P less than 0.003), but there was no change in total plasma cholesterol concentration or urinary protein excretion. Platelet function was studied in nine patients. Platelet aggregation induced by adrenaline and collagen was reduced by fish oils (median change in per cent aggregation), adrenaline 2 mumols/l, -36% (95% CI -68%, -8%, P less than 0.05), collagen 1 mg/1, -13% (95% CI -44%, -2%, P less than 0.05). Platelet thromboxane A2 release in response to these agents was also significantly reduced. These results demonstrate that fish oils preserve residual function in renal graft failure due to chronic vascular rejection.