Transporter Polymorphism Research Articles

Personalized statin therapy: Targeting metabolic processes to modulate the therapeutic and adverse effects of statins.

Statins are widely used for treating lipid disorders and cardiovascular diseases. However, the therapeutic efficiency and adverse effects of statins vary among different patients, which numerous clinical and epidemiological studies have attributed to genetic polymorphisms in statin-metabolizing enzymes and transport proteins. The metabolic processes of statins are relatively complex, involving spontaneous or enzyme-catalyzed interconversion between more toxic lactone metabolites and active acid forms in the liver and bloodstream, influenced by multiple factors, including the expression levels of many metabolic enzymes and transporters. Addressing the variable statin therapeutic outcomes is a pressing clinical challenge. Transcription factors and epigenetic modifications regulate the metabolic enzymes and transporters involved in statin metabolism and disposition and, therefore, hold promise as 'personalized' targets for achieving optimized statin therapy. In this review, we explore the potential for customizing therapy by targeting the metabolism of statin medications. The biochemical bases of adverse reactions to statin drugs and their correlation with polymorphisms in metabolic enzymes and transporters are summarized. Next, we mainly focus on the regulatory roles of transcription factors and epigenetic modifications in regulating the gene expression of statin biochemical machinery. The recommendations for future therapies are finally proposed by targeting the central regulatory factors of statin metabolism.

Mice lacking the serotonin transporter do not respond to the behavioural effects of psilocybin.

Psilocybin is a serotonergic psychedelic with therapeutic potential for several neuropsychiatric disorders, including depression and anxiety disorders. Serotonin transporter (5-HTT) knockout mice (KO) are a well-validated mouse model of anxiety/depression and are relevant to both chronic treatment with serotonin transporter reuptake inhibitors (SSRIs) and polymorphisms in the serotonin transporter-linked polymorphic region (5-HTTLPR) associated with depression/anxiety and resistance to classic antidepressant treatments. However, there is yet to be a study assessing the effect of psilocybin in 5-HTT KO mice. We investigated the effects of a single dose of psilocybin (1mg/kg) on locomotor activity and the head-twitch response as well as anxiety- and depressive-like behaviour in KO versus wild-type (WT) mice using the light-dark box and Porsolt swim test respectively. We found that both the psilocybin-induced head-twitch and hyperlocomotor responses observed in WT mice were completely absent in KO animals. In female WT mice only, psilocybin was also able to block the weight loss observed one day after intraperitoneal injection. While psilocybin did not alter anxiety- and depression-like behaviours for both genotypes, we revealed a genotype-specific trend for a main effect of treatment for WT females (p=0.054) in the Porsolt swim test. Finally, we found that only female KO mice exhibit anhedonia-like behaviour in the saccharin-preference test. Our findings highlight the complexity of psilocybin's effects and suggest that functional integrity of 5-HTT is essential for psilocybin's acute behavioural effects. This could also have implications for pharmacogenetics, including individuals with polymorphisms or mutations in 5-HTT.

Evaluation of single nucleotide polymorphisms in the human norepinephrine transporter (hNET) gene for structural, functional, and pathogenic significance

The norepinephrine transporter (NET) is a key regulator of noradrenergic neurotransmission and homeostasis, regulating the norepinephrine levels in the brain and peripheral tissues. hNET is a major target in neuropsychiatric disorders such as major depressive disorder, autonomic dysfunction, and attention deficit hyperactivity disorder (ADHD). The human norepinephrine transporter gene (hNET, SLC6A2) contains 504 missense single nucleotide polymorphisms (SNPs). These SNPs have been identified in public databases. Elucidating the molecular effects of missense SNPs on hNET protein function and structure may provide insight into how hNET missense SNPs affect the biological activity of the protein and contribute to the etiopathogenesis of disease. Therefore, in our study, we aimed to analyze the structural, functional, and pathogenic effects of genetic variants in the human SLC6A2 gene using various bioinformatics tools. In our study, rs45564432 (T283R), rs121918126 (A457P), rs5558 (F528C), rs5566 (A369P), rs13306041 (R121Q), rs147833183 (R301H), rs201263363 (Y294H), rs201586185 (A369V), and rs373891109 (T258I) variants have been identified as pathogenic with structural and functional effects. Our results demonstrated the significance of hNET high-risk missense SNPs on the function and structure of the transporter protein. We anticipate that the results of this study will contribute to future experimental studies investigating the relationship between hNET genetic variants and the pathogenesis and treatment of neuropsychiatric disorders.

Analysis of <em>Pfmdr1</em> and <em>Pfcrt drug</em> resistant markers in <em>Plasmodium falciparum</em> following treatments of patients from Nyando and Mbita, Nyanza region with Artemisinin-based combination therapy

The multidrug resistance of Plasmodium falciparum to antimalarial drugs is a major public health concern in the global management of malaria, especially in developing countries. As of today, malaria treatment is primarily dependent on the sustained efficacy of artemisinin-based combination therapy (ACT). Recent reports indicating decline in efficacy of ACT and artesunate monotherapy in Southeast Asia are a major threat to global malaria control achievements. Initially, mutations in Pfmdr1 were associated with chloroquine and amodiaquine resistance only, but there are now emerging field study reports of Pfmdr1 mutation conferring tolerance to ACT. The current study used Restriction Fragment Length Polymorphism to evaluate the prevalence of genetic polymorphisms of Plasmodium falciparum multidrug resistance (Pfmdr1) and Plasmodium falciparum chloroquine-resistant transporter (Pfcrt) gene mutations in Mbita and Nyando field isolates. The findings report that the prevalence of Pfcrt K76T mutation in Plasmodium falciparum field isolates in Mbita declined significantly from 76.3% (95% CI 21.0-31.0) in 2008 to 51.9% (95% CI 19.0-25.0) in 2014, a reduction of 24.4% (χ2df =1 = 4.709, P = 0.0000). In Nyando, prevalence stood at 66.8% (95% CI 12.0-14.0) in 2014 down from 73.7% (95% CI 27.0-48.0), insignificant reduction of 6.9% (χ2df =1 = 17.699, P = 0.0913). Prevalence for Pfmdr1 in Mbita stood at 14.7% (95% CI 44.0-51.0) in 2014 down from 21.9% (95% CI 31.0-49.0) in 2008, a significant reduction of 4.3% (χ2df =1 = 9.011, P = 0.001). While in Nyando, field isolate samples recorded 16.2% (95% CI 22.0-31.0) in 2014, down from 30.6% (95% CI 12.0-27.0), insignificant reduction of 1.9% (χ2df =1 = 11.777, P = 0.0591). Our findings confirm a common trend reported by previous studies: that there has been a small decline in the prevalence of the Pfcrt mutation over a decade since the withdrawal of Chloroquine as the first line of treatment for uncomplicated cases of malaria in Kenya.

Distribution Clearance: Significance and Underlying Mechanisms

PurposeEvaluation of distribution kinetics is a neglected aspect of pharmacokinetics. This study examines the utility of the model-independent parameter whole body distribution clearance (CLD) in this respect.MethodsSince mammillary compartmental models are widely used, CLD was calculated in terms of parameters of this model for 15 drugs. The underlying distribution processes were explored by assessment of relationships to pharmacokinetic parameters and covariates.ResultsThe model-independence of the definition of the parameter CLD allowed a comparison of distributional properties of different drugs and provided physiological insight. Significant changes in CLD were observed as a result of drug-drug interactions, transporter polymorphisms and a diseased state.ConclusionTotal distribution clearance CLD is a useful parameter to evaluate distribution kinetics of drugs. Its estimation as an adjunct to the model-independent parameters clearance and steady-state volume of distribution is advocated.

Developmental cascades from early childhood attachment security to adolescent level of personality functioning among high-risk youth.

This study examines associations between early childhood attachment security and adolescent personality functioning in a high-risk sample within a developmental psychopathology framework. Data from 2,268 children (1165 male; 1103 female) and caregivers participating in Future of Families and Child Well-Being Study (FFCWS) were used to examine (1) effects of genetic polymorphisms of the serotonin transporter (5-HTTLPR) and dopamine D4 receptor (DRD4) genes and adverse childhood experiences (ACEs) on attachment security and emotional and behavioral dysregulation in early childhood and (2) longitudinal associations and transactional relationships among attachment security, dysregulation, negative parenting attitudes and behaviors, social competence, and adolescent personality functioning. Results revealed that ACEs predicted attachment security over and above sex or the genetic risk, and gene × environment interactions did not increment prediction. Results of cascade models showed that greater early childhood attachment security predicted higher adolescent level of personality functioning via pathways through intermediary variables. Limitations and future research directions are discussed.

Evidence for a relationship between genetic polymorphisms of the L-DOPA transporter LAT2/4F2hc and risk of hypertension in the context of chronic kidney disease

BackgroundChronic kidney disease (CKD) and hypertension are chronic diseases affecting a large portion of the population frequently coexistent and interdependent. The inability to produce/use adequate renal dopamine may contribute to the development of hypertension and renal dysfunction. The heterodimeric amino acid transporter LAT2/4F2hc (SLC7A8/SLC3A2 genes) promotes the uptake of L-DOPA, the natural precursor of dopamine. We examined the plausibility that SLC7A8/SLC3A2 gene polymorphisms may contribute to hypertensive CKD by affecting the L-DOPA uptake.Methods421 subjects (203 men and 218 women, mean age of 78.9 ± 9.6 years) were recruited and divided in four groups according to presence/absence of CKD, defined as reduced estimated glomerular filtration rate (eGFR < 60 ml/min/m2) calculated using the creatinine-based Berlin Initiative Study–1 (BIS1) equation, and to presence/absence of hypertension (systolic blood pressure ≥ 140 and/or diastolic blood pressure ≥ 90 mmHg). Subjects were analysed for selected SNPs spanning the SLC7A8 and SLC3A2 loci by Sequenom MassARRAY iPLEX platform.ResultsThe most significant SNP at the SLC3A2 (4F2hc) locus was rs2282477-T/C, with carriers of the C-allele having a lower chance to develop hypertension among CKD affected individuals [OR = 0.33 (CI 0.14–0.82); p = 0.016]. A similar association with hypertensive CKD was found for the SLC7A8 (LAT2) rs3783436-T/C, whose C-allele resulted associated with decreased risk of hypertension among subjects affected by CKD [OR = 0.56 (95% CI 0.35–0.90; p = 0.017]. The two variants were predicted to be potentially functional.ConclusionsThe association between SLC3A2 and SLC7A8 variants to hypertension development in patients with renal failure could be linked to changes in L-DOPA uptake and consequently dopamine synthesis. Although the associations do not survive correction for Bonferroni multiple testing, and additional research is needed, our study opens new avenues for future basic and translational research in the field of hypertensive CKD.

Association between plasma imatinib levels and response to treatment of chronic myeloid leukemia in patients from Manaus, Brazil.

Imatinib mesylate (IM) is the drug of choice for the treatment of chronic myeloid leukemia (CML). However, despite most of the results obtained with this therapy being positive, some patients still present a suboptimal therapeutic response or still develop some type of resistance. Therefore, the aim of this study was to evaluate IM plasma levels in CML patients treated at a referral unit in Manaus and correlate them with variables that might interfere with these levels. Data from 52 patients were obtained through a standardized questionnaire containing clinical, sociodemographic, lifestyle, and use of other medication information, as well as an estimate of therapeutic adherence. Additionally, blood collection was performed to measure the plasma concentration of the drug using the HPLC-UV technique. Molecular studies were done to identify the presence of polymorphism in the ABCG2 C421A membrane transporter. Most patients were male with a mean age of 52 ± 12.3 years (95% CI 49.0-55.9). There was a high variation in drug concentrations in the range from 0 to 4694 ng/mL, with a mean of 1558.59 ± 989.79 ng/mL (95% CI 1283.0-1834.1). Approximately two-thirds of patients were classified in the drug-level range considered therapeutic, and there was a correlation between plasma concentration and higher molecular response. Additionally, most individuals had the normal genotype for the ABCG2 C421A polymorphism but further studies should be performed to reveal the role of this variable in the outcome of the disease in this population.

Tailoring Type II Diabetes Treatment: Investigating the Effect of 5-HTT Polymorphisms on HbA1c Levels after Metformin Initiation.

To investigate the effect of serotonin transporter (5-HTT) polymorphisms on change in HbA1c levels six months after metformin initiation in type 2 diabetes patients. Participants of PROVALID (PROspective cohort study in patients with type 2 diabetes mellitus for VALidation of biomarkers) within the GIANTT (Groningen Initiative to ANalyse Type 2 Diabetes Treatment) cohort who initiated metformin were genotyped for combined 5-HTTLPR/rs25531 (L∗L∗, L∗S∗, and S∗S∗) and 5-HTT VNTR (STin 2.12, 12/-, and 10/-) polymorphisms, respectively. Multiple linear regression was applied to determine the change in HbA1c level from baseline date to six months across 5-HTTLPR/VNTR genotype groups, adjusted for baseline HbA1c, age, gender, triglyceride level, low-density lipoprotein level, and serum creatinine. 157 participants were included, of which 56.2% were male. The average age was 59.3 ± 9.23 years, and the mean baseline HbA1c was 7.49% ± 1.21%. 5-HTTLPR was characterized in 46 patients as L∗L∗, 70 patients as L∗S∗, and 41 patients as S∗S∗ genotypes. No significant association was found between 5-HTTLPR and 5-HTT VNTR genotypes and change in HbA1c after adjustments. 5-HTT polymorphisms did not affect HbA1c levels six months after the start of metformin. Further long-term studies in large samples would be relevant to determine which polymorphisms can explain the variation in response to metformin treatment.

Phosphoproteomics implicates glutamatergic and dopaminergic signalling in the antidepressant-like properties of the iron chelator deferiprone

Current antidepressants have limitations due to insufficient efficacy and delay before improvement in symptoms. Polymorphisms of the serotonin transporter (5-HTT) gene have been linked to depression (when combined with stressful life events) and altered response to selective serotonergic reuptake inhibitors. We have previously revealed the antidepressant-like properties of the iron chelator deferiprone in the 5-HTT knock-out (KO) mouse model of depression. Furthermore, deferiprone was found to alter neural activity in the prefrontal cortex of both wild-type (WT) and 5-HTT KO mice. In the current study, we examined the molecular effects of acute deferiprone treatment in the prefrontal cortex of both genotypes via phosphoproteomics analysis. In WT mice treated with deferiprone, there were 22 differentially expressed phosphosites, with gene ontology analysis implicating cytoskeletal proteins. In 5-HTT KO mice treated with deferiprone, we found 33 differentially expressed phosphosites. Gene ontology analyses revealed phosphoproteins that were predominantly involved in synaptic and glutamatergic signalling. In a drug-naïve cohort (without deferiprone administration), the analysis revealed 21 differentially expressed phosphosites in 5-HTT KO compared to WT mice. We confirmed the deferiprone-induced increase in tyrosine hydroxylase serine 40 residue phosphorylation (pTH-Ser40) (initially revealed in our phosphoproteomics study) by Western blot analysis, with deferiprone increasing pTH-Ser40 expression in WT and 5-HTT KO mice. As glutamatergic and synaptic signalling are dysfunctional in 5-HTT KO mice (and are the target of fast-acting antidepressant drugs such as ketamine), these molecular effects may underpin deferiprone's antidepressant-like properties. Furthermore, dopaminergic signalling may also be involved in deferiprone's antidepressant-like properties.

Allele frequencies and genotype distribution of three metformin transporter polymorphisms in Mexican population and their application in pharmacogenomics of type 2 diabetes.

Metformin is the first-line antidiabetic therapy for type 2 diabetes in Mexico, despite recent recommendations highlighting alternatives like GLP-1 receptor agonists for individuals with obesity. Metformin elimination is reliant on liver and kidney function, and variants in transport proteins such as Multidrug and Toxin Extrusion Protein 1 (MATE1), MATE2, and Organic Cation Transporter 2 (OCT2) can influence its pharmacokinetics. Understanding these variants' frequencies in the Mexican population is crucial for tailoring personalized treatment strategies. This study aimed to determine the genotypic and allelic frequencies of key variants in metformin transporters within a Mexican population, addressing the interindividual variability in drug response. Genetic analysis was conducted on 101 healthy, unrelated Mexican subjects who were genotyped for the MATE1, MATE2, and OCT2 variants using allele-specific real-time PCR assays. The allele frequencies were 0.07 for OCT2, 0.23 for MATE1, and 0.67 for MATE2. The g.-66T→C variant was found only in wild-type and heterozygous forms. Comparative analysis indicated significant differences in allele frequencies between this Mexican population and other ethnic groups, highlighting potential implications for metformin efficacy and safety. This study provides crucial insights into the genetic variability of metformin transporter genes in a Mexican population, offering a foundation for personalized therapeutic approaches in type 2 diabetes management.

The Evolving Landscape of Gout in the Female: A Narrative Review

Gout is at least three times more prevalent in males than in females. However, concurrent with rising total gout prevalence, complex factors, including comorbidities, diet, lifestyle, and aging, have promoted higher gout prevalence in females. This narrative review focuses on summarizing recent developments in the landscape of gout in females and the mechanisms involved. New knowledge on sex hormone effects on both urate-excreting and urate-reabsorbing transporters and higher hypertension and chronic kidney disease prevalence in females compared to males may help explain why gout incidence rises robustly after menopause in females, to approach that in males. Racial and ethnic factors, risk profiles based on heritable genetic polymorphisms of urate transporters, diet, body mass index, and lifestyle factors differ according to sex. In addition, sex differences in clinical phenotypes, outcomes of gout, and non-gout illnesses include more frequent comorbidities, more pain and disability during gout flares, different perceptions of disease burden, and more frequent severe cutaneous hypersensitivity reaction to allopurinol in females. Collectively, such findings support the potential clinical benefits of tailoring gout and hyperuricemia treatment according to sex.

Polymorphisms in Drug Transporter and Metabolism Genes Associated with Resistance to Imatinib in Chronic Myeloid Leukemia: A Systematic Review and Meta-Analysis

The aim of this study was to establish the relationship between different polymorphisms in drug transporter and metabolizer genes and resistance to imatinib in chronic myeloid leukemia (CML). For this purpose, an exhaustive search was carried out in the Scopus, Web of Science, and PubMed databases using different combinations of keywords with different inclusion and exclusion criteria. The meta-analysis included nine studies that met the established criteria. The results of the study showed that the polymorphic variants AG and GG of CYP3A5*3 are associated with response to treatment, presenting a significantly lower risk with resistance to imatinib. Likewise, the variants T1236C and G2677T/A of the ABCB1 gene show a significant association with treatment efficacy. In addition, the genetic polymorphism 1236T, homozygous CC of the MDR1 gene, significantly influences the increased risk of cytogenetic relapse and the polymorphic variant 361G&gt;A GA of the SLCO1A2 gene significantly affects the complete molecular response.

Effect of genetic polymorphisms on the pharmacokinetics of gefitinib in healthy Chinese volunteers

Gefitinib is the first-generation drug of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) metabolised by the cytochrome P450 and transported by P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2). In the present study, the pharmacokinetics of gefitinib in healthy Chinese volunteers was investigated and the effect of genetic polymorphisms on its variability was evaluted. Forty-five healthy volunteers were administered a single dose of gefitinib and the blood samples were used for quantifying the concentration of gefitinib and genotyping fifteen single-nucleotide polymorphisms of cytochrome P450 enzymes (CYP3A4, CYP3A5, CYP2D6, CYP2C9 and CYP2C19) and drug transporters (ABCB1 and ABCG2). CYP3A5*3 (rs776746) polymorphism showed a significant influence, with higher gefitinib AUC0-t in carrier of CC genotype than in CT/TT genotype (BH-adjusted p value <0.05). For CYP2C9*3 (rs1057910), significant differences in pharmacokinetics of gefitinib were detected between carriers of AA and AC genotypes, with higher AUC0-t, AUC0-∞ and Cmax in carrier of AC genotype than in AA gen-otype (BH-adjusted p value <0.05). No associations were found between SNPs in CYP3A4, CYP2D6, CYP2C19, ABCB1, ABCG2 and the pharmacokinetics of gefitinib. The SNPs in CYP3A5*3 (rs776746) and CYP2C9*3 (rs1057910) were found to be associated with altered gefitinib pharmacokinetics in healthy Chinese volunteers.

CYP450 and drug efflux transporters polymorphism influence clinical outcomes of Thai osimertinib-treated non-small cell lung cancer patients.

Background: Osimertinib has shown greater efficacy than standard epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) and fewer grade 3 or higher adverse drug reactions (ADRs) in patients with advanced non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations. However, the clinical outcomes of osimertinib treatment vary depending on the patient's ethnicity. Therefore, further research is necessary to evaluate the impact of single nucleotide polymorphisms (SNPs) in cytochrome P450 (CYP450) and drug transporters on the therapeutic outcomes and ADRs to osimertinib in Thai patients, to provide improved pharmacological treatments for cancer patients. Methods: This retrospective and prospective cohort study enrolled 63 Thai patients with NSCLC treated with 80mg of osimertinib once daily as monotherapy. Seventeen SNPs in candidate genes related to drug metabolism and transport pathways were analyzed in each patient. Chi-square or Fisher's exact tests were used to evaluate the associations between SNPs and clinical outcomes, including ADR incidence and objective response rate (ORR). In addition, the correlation between the genotype and median time to treatment failure (TTF) or progression-free survival (PFS) was assessed using Kaplan-Meier analysis and a log-rank test. Results: We identified six SNPs (rs2231142 and rs2622604 in ABCG2, rs762551 in CYP1A2, rs1057910 in CYP2C9, rs28371759 in CYP3A4, and CYP2A6 deletion polymorphism (CYP2A6*4)) that significantly increased the incidence of ADRs. In addition, we found two SNPs (rs2069514 in CYP1A2 and rs1057910 in CYP2C9) that significantly decreased the median TTF, and two SNPs (rs28399433 in CYP2A6 and rs1057910 in CYP2C9) that significantly decreased the median progression-free survival (PFS). Specifically, we found that one of these SNPs (rs1057910 in CYP2C9) influenced ADRs, TTF, and PFS. Additionally, SNPs in the CYP2A6 heterozygous variant (non4/*4) significantly increased ADR incidence, leading to a high frequency of dose reduction (27.0%). Conclusion: Our study demonstrated significant SNPs associated with increased ADR incidence, decreased PFS, and decreased TTF in Thai patients with NSCLC treated with osimertinib. The CYP2C9 (*3) and CYP2A6 (*4) allele frequencies differed between ethnicities and were associated with an increased incidence of ADRs. These findings highlight the importance of considering genetic factors in NSCLC treatment and may facilitate personalized medicine approaches. Moreover, our study showed a higher incidence of ADRs than the previous trials, including FLAURA and AURA2, and a higher frequency of dose reduction than reported in the AURA 3 trial, possibly due to genetic differences among the study populations.

The Impact of Certain Pharmacogenetic Differences on the Metabolism of Antiretroviral Drugs Used in A Black South African Population.

Genetic polymorphism of drug-metabolising enzymes and transporters may influence the effect and toxicity of antiretroviral drugs. To determine and compare the minimum allele frequency of 20 single nucleotide polymorphisms (SNPs) with possible involvement in the metabolism of the antiretroviral drugs with other populations. To investigate the influence of these variants on Reverse transcriptase, Protease and Integrase strand transfer inhibitor drugs. DNA samples were collected from 1489 subjects. All SNPs with a gene call score of > 0.6 were selected for genotyping. The R package calculated call rates, MAF and Hardy-Weinberg equilibrium (HWE), test p-values, and Chi-squared analysis were performed on the data. The Fisher's exact test compared the allele frequencies between the populations. The highest similarities in minimum allele frequency (MAF) were between the Prospective Urban and Rural Epidemiological group (PURE), a Black population in South Africa, and the Yoruba and Luhya populations in Africa. The following SNPs were identified with a possible effect on metabolism: CYP2B6 rs28399494 (MAF 11%) is indicated in the toxicity of Efavirenz and Nevirapine. CYP3A5 rs776746 (MAF 17%) and CYP3A4 rs2749674 (MAF 23%) both cause an increase in the metabolism of the protease inhibitors. The very low MAF values for both SCL01B1 rs4149056 (MAF 0.6%) and ABCC rs717620 (MAF 2.8%) are indications that OATP1B1 transport function and glomerular filtration tempo will not be compromised. The high MAF value of 30% for UGTA1 rs10929302 can result in hyperbilirubinemia, which can decrease the clearance of Dolutegravir. These results show a possibility of kidney protection and an increase in bilirubin in this population.

Serotonin and Depression: Scrutiny of New Targets for Future Anti-Depressant Drug Development.

The "serotonin hypothesis of depression" is approximately fifty years old, and in spite of vast literature, the exact role of serotonin in depression pathophysiology is still unclear, as whether a lower serotonin level causes depression or depression causes a reduction in serotonin level has become a tough challenge for researchers to understand the actual involvement of serotonin in depression. Several pre-clinical and clinical studies have illustrated the multi-faceted signalling action of serotonin in depression and vouch for the significant or unavoidable role of serotonin in depression. In this review, the journey of the serotonin hypothesis of depression from the 1950s to the present time has been analysed to understand the serotonin hypothesis of depression and investigate the new molecular targets for the development of new future anti- depressants. The old and new theories of possible cellular mechanisms found to be involved in the pathophysiology of major depression or stress, such as polymorphism of serotonin transporters, enzyme modulating serotonergic activity, reduction in the level of serotonin and involvement of different sub-types of receptors, have been discussed in the respective review. Thus, in this review, the new signature targets to increase serotonin levels have been identified, which would help the researcher in the drug development of new faster-acting antidepressants.

Single-nucleotide polymorphisms in ABC drug transporters alter expression and circulating tenofovir in healthy South African women exposed to pre-exposure prophylaxis.

Aim: We investigated if single-nucleotide polymorphisms (SNPs) in ATP-binding cassette (ABC)drug transporters alter gene expression and tenofovir disposition in South African women taking Truvada® for HIV prevention. Materials & methods: In 393 women, real-time PCR was used to determine the associations between six SNPs in ABC transporter genes, mRNA expression and circulating-tenofovir. Results: Univariable and multivariable analyses showed that CT and TT relative to CC genotypes for theABCC4(3463C/T) SNPhad significantly higher tenofovir levels. In contrast, the AA genotype for the ABCC4(4976A/G) SNP showed significantly less tenofovir, while mRNA expression was increased. Conclusion: SNPs in the ABCC4 gene may differentially affect gene expression and circulating tenofovir. Their impact may inform on low pre-exposure prophylaxis efficacy and discern effective drugs in clinical trials of African women enriched for certain genotypes.

Epitope specific antibodies to N- and C cytoplasmic domains of the Plasmodium falciparum chloroquine resistance transporter (PfCRT) differentiate native and post-translationally modified variant

Polymorphisms in Plasmodium falciparum chloroquine resistance transporter (or PfCRT) were shown to be causative of decreased sensitivity to diverse quinoline-based antimalarials. In this report we describe the identification of a post-translational variant of PfCRT using highly characterized antibodies raised against its N- and C-terminal cytoplasmic domains (e.g., 58 and 26 amino acids, respectively). Western blot analyses of P.falciparum protein extracts with anti N-PfCRT antiserum revealed two polypeptides with apparent molecular masses of 52kDa and 42kDa, relative to the calculated molecular mass of PfCRT of 48.7kDa. The 52kDa polypeptide was detectable with anti C-PfCRT antiserum, only after alkaline phosphatase treatment of P.falciparum extracts. Detailed epitope mapping of anti N- and C-PfCRT antisera revealed epitopes covering two previously identified phosphorylation sites, Ser411 and Thr416, whereby substitution of these residues with Asp amino acid, to mimic phosphorylated residues, dramatically inhibited anti C-PfCRT binding. Consistently, alkaline phosphatase treatment of P.falciparum extract unmasked the binding of anti C-PfCRT to the 52kDa polypeptide, suggesting that the 52kDa but not 42kDa polypeptide is phosphorylated at its C-terminal Ser411 and Thr416. Interestingly, Pfcrt expressed in HEK-293F human kidney cells showed the same reactive polypeptides with anti N- and C-PfCRT antisera, consistent with PfCRT origin of the two polypeptides (e.g., 42kDa and 52kDa), but lacking PfCRT phosphorylation at its C-terminal. Immunohistochemical staining of late trophozoite-infected erythrocytes with anti N-or C-PfCRT antisera showed both polypeptides are localized to the parasite's digestive vacuole. Moreover, both polypeptides are detected in chloroquine-susceptible and -resistant strains of P.falciparum. This is the first report describing a post-translationally modified variant of PfCRT. The physiologic role of the 52kDa phosphorylated PfCRT in P.falciparum remains to be determined.

Identification of Transporter Polymorphisms Influencing Metformin Pharmacokinetics in Healthy Volunteers

For patients with type 2 diabetes, metformin is the most often recommended drug. However, there are substantial individual differences in the pharmacological response to metformin. To investigate the effect of transporter polymorphisms on metformin pharmacokinetics in an environment free of confounding variables, we conducted our study on healthy participants. This is the first investigation to consider demographic characteristics alongside all transporters involved in metformin distribution. Pharmacokinetic parameters of metformin were found to be affected by age, sex, ethnicity, and several polymorphisms. Age and SLC22A4 and SLC47A2 polymorphisms affected the area under the concentration-time curve (AUC). However, after adjusting for dose-to-weight ratio (dW), sex, age, and ethnicity, along with SLC22A3 and SLC22A4, influenced AUC. The maximum concentration was affected by age and SLC22A1, but after adjusting for dW, it was affected by sex, age, ethnicity, ABCG2, and SLC22A4. The time to reach the maximum concentration was influenced by sex, like half-life, which was also affected by SLC22A3. The volume of distribution and clearance was affected by sex, age, ethnicity and SLC22A3. Alternatively, the pharmacokinetics of metformin was unaffected by polymorphisms in ABCB1, SLC2A2, SLC22A2, or SLC47A1. Therefore, our study demonstrates that a multifactorial approach to all patient characteristics is necessary for better individualization.