Dopamine, empathy and the neurobiology of leadership

Objectives: Organisational Psychologists have long sought after methods by which to train individuals to become more effective leaders. Indeed considerable sums of money are spent on the design of such training programs. Yet it is not clear whether or not leadership skills can be taught or whether they are innate. Social leadership is a varied construct consisting of many diverse aspects, yet the ability to empathise with subordinates is a core skill that underpins effective transformational leadership. This type of leadership consists of four characteristics which are labelled ‘idealized influence’, ‘inspirational motivation’, ‘intellectual stimulation’ and ‘individualized consideration’. This is distinct from the transactional style of leadership, which is based on offering contingent rewards for completion of specific tasks. By identifying a specific gene that mediates distinct leadership traits, more effective training regimes can be designed. Design: There are two likely candidate genes that may mediate empathic leadership. The first is catechol-O-methyltransferase (COMT) which is involved with dopamine synthesis, and the second is the serotonin transporter promoter gene (5-HTTLPR). Both these genes mostly appear in the general population in their heterozygotic form. Thus by comparing phenotypes in leadership traits a measure of base line differences can be examined. Methods: 115 volunteers completed the Multifactor Leadership questionnaire (MLQ), which is a standard 12-item leadership psychometric scale and also underwent buccal swab for subsequent genotyping. Results: Of the 115 subjects 37 were heterozygotic for the COMT gene and 47 heterozygotic for 5-HTTLPR. Of the 12 MLQ subscales, the scores for two of the subscales only differed between the two participant groups. Individuals who were heterozygotic for the COMT gene scored higher on the ‘Inspirational motivation’ t(84)=1.99, p=0.05 and ‘Intellectual stimulation’ t(82)=1.94, p=0.05 scales compared to the carriers for the heterozygotic 5HTPP gene. Conclusions: Given that the behaviours described by these two MLQ subscales require leaders to empathise with subordinates, the current results suggest that dopamine may play a role in this important social task. The fact that both heterozygotic carriers for COMT and 5HTPP were compared allows a comparison to be made between the genotypes most prevalent in the general population.

Psychophysiological responses to pain identify reproducible human clusters

Pain is a ubiquitous yet highly variable experience. The psychophysiological and genetic factors responsible for this variability remain unresolved. We hypothesised the existence of distinct human pain clusters (PCs) composed of distinct psychophysiological and genetic profiles coupled with differences in the perception and the brain processing of pain. We studied 120 healthy subjects in whom the baseline personality and anxiety traits and the serotonin transporter-linked polymorphic region (5-HTTLPR) genotype were measured. Real-time autonomic nervous system parameters and serum cortisol were measured at baseline and after standardised visceral and somatic pain stimuli. Brain processing reactions to visceral pain were studied in 29 subjects using functional magnetic resonance imaging (fMRI). The reproducibility of the psychophysiological responses to pain was assessed at 1 year. In group analysis, visceral and somatic pain caused an expected increase in sympathetic and cortisol responses and activated the pain matrix according to fMRI studies. However, using cluster analysis, we found 2 reproducible PCs: at baseline, PC1 had higher neuroticism/anxiety scores (P ≤ 0.01); greater sympathetic tone (P < 0.05); and higher cortisol levels (P ≤ 0.001). During pain, less stimulus was tolerated (P ≤ 0.01), and there was an increase in parasympathetic tone (P ≤ 0.05). The 5-HTTLPR short allele was over-represented (P ≤ 0.005). PC2 had the converse profile at baseline and during pain. Brain activity differed (P ≤ 0.001); greater activity occurred in the left frontal cortex in PC1, whereas PC2 showed greater activity in the right medial/frontal cortex and right anterior insula. In health, 2 distinct reproducible PCs exist in humans. In the future, PC characterization may help to identify subjects at risk for developing chronic pain and may reduce variability in brain imaging studies. © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Amino acids in oral drug delivery:salts, ion-pairs and transcriptomics

Oral drug delivery is considered the most popular route of delivery because of the ease of administration, availability of a wide range of dosage forms and the large surface area for drug absorption via the intestinal membrane. However, besides the unfavourable biopharmaceutical properties of the therapeutic agents, efflux transporters such as Pglycoprotein (P-gp) and multiple resistance proteins (MRP) decrease the overall drug uptake by extruding the drug from the cells. Although, prodrugs have been investigated to improve drug partitioning by masking the polar groups covalently with pre-moieties promoting increased uptake, they present significant challenges including reduced solubility and increased toxicity. The current work investigates the use of amino acids as ion-pairs for three model drugs: indomethacin (weak acid), trimethoprim (weak base) and ciprofloxacin (zwitter ion) in an attempt to improve both solubility and uptake. Solubility was studied by salt formation while creating new routes for uptake across the membranes via amino acids transporter proteins or dipeptidyl transporters was the rationale to enhance absorption. New salts were prepared for the model drugs and the oppositely charged amino acids by freeze drying and they were characterised using FTIR, 1HNMR, DSC, SEM, pH solubility profile, solubility and dissolution. Permeability profiles were assessed using an in vitro cell based method; Caco-2 cells and the genetic changes occurring across the transporter genes and various pathways involved in the cellular activities were studied using DNA microarrays. Solubility data showed a significant increase in drug solubility upon preparing the new salts with the oppositely charged counter ions (ciprofloxacin glutamate salt exhibiting 2.9x103 fold enhancement when compared to the free drug). Moreover, permeability studies showed a 3 fold increase in trimethoprim and indomethacin permeabilities upon ion-pairing with amino acids and more than 10 fold when the zwitter ionic drug was paired with glutamic acid. Microarray data revealed that trimethoprim was absorbed actively via OCTN1 transporters while MRP7 is the main transporter gene that mediates its efflux. The absorption of trimethoprim from trimethoprim glutamic acid ion-paired formulations was affected by the ratio of glutamic acid in the formulation which was inversely proportional to the degree of expression of OCTN1. Interestingly, ciprofloxacin glutamic acid ion-pairs were found to decrease the up-regulation of ciprofloxacin efflux proteins (P-gp and MRP4) and over-express two solute carrier transporters; (PEPT2 and SLCO1A2) suggesting that a high aqueous binding constant (K11aq) enables the ion-paired formulations to be absorbed as one entity. In conclusion, formation of ion-pairs with amino acids can influence in a positive way solubility, transfer and gene expression effects of drugs.

Genetic modulation of the response bias towards facial displays of anger and happiness

Background: Investigating genetic modulation of emotion processing may contribute to the understanding of heritable mechanisms of emotional disorders. The aim of the present study was to test the effects of catechol- O-methyltransferase (COMT) val158met and serotonin-transporter-linked promoter region (5-HTTLPR) polymorphisms on facial emotion processing in healthy individuals. Methods: Two hundred and seventy five (167 female) participants were asked to complete a computerized facial affect recognition task, which involved four experimental conditions, each containing one type of emotional face (fearful, angry, sad or happy) intermixed with neutral faces. Participants were asked to indicate whether the face displayed an emotion or was neutral. The COMT-val158met and 5-HTTLPR polymorphisms were genotyped. Results: Met homozygotes (COMT) showed a stronger bias to perceive neutral faces as expressions of anger, compared with val homozygotes. However, the S-homozygotes (5-HTTLPR) showed a reduced bias to perceive neutral faces as expressions of happiness, compared to L-homozygotes. No interaction between 5-HTTLPR and COMT was found. Conclusions: These results add to the knowledge of individual differences in social cognition that are modulated via serotonergic and dopaminergic systems. This potentially could contribute to the understanding of the mechanisms of susceptibility to emotional disorders. © 2013 Elsevier Masson SAS.

Genomic evaluation during permeability of indomethacin and its solid dispersion

Drug resistance was first identified in cancer cells that express proteins known as multidrug resistance proteins that extrude the therapeutic agents out of the cells resulting in alteration of pharmacokinetics, tissue distribution, and pharmacodynamics of drugs. To this end studies were carried out to investigate the role of pharmacological inhibitors and pharmaceutical excipients with a primary focus on P-glycoprotein (P-gp). The aim of this study was to investigate holistic changes in transporter gene expression during permeability upon formulation of indomethacin as solid dispersion. Initial characterization studies of solid dispersion of indomethacin showed that the drug was dispersed within the carrier in amorphous form. Analysis of permeability data across Caco-2 monolayers revealed that drug absorption increased by 4-fold when reformulated as solid dispersion. The last phase of the work involved investigation of gene expression changes of transporter genes during permeability. The results showed that there were significant differences in the expression of both ATP-binding cassette (ABC) transporter genes as well as solute carrier transporter (SLC) genes suggesting that the inclusion of polyethylene glycol as well as changes in molecular form of drug from crystalline to amorphous have a significant bearing on the expression of transporter network genes resulting in differences in drug permeability. © 2011 Informa UK, Ltd.

Linking gene expression in the intestine to production of gametes through the phosphate transporter PITR-1 in Caenorhabditis elegans

Inorganic phosphate is an essential mineral for both prokaryotic and eukaryotic cell metabolism and structure. Its uptake into the cell is mediated by membrane bound transporters and coupled to Na+ transport. Mammalian sodium-dependent Pi co-transporters have been grouped into three families NaPi-I, NaPi-II, and NaPi-III. Despite being discovered more than 2 decades ago, very little is known about requirements for NaPi-III transporters in vivo, in the context of intact animal models. Here we find that impaired function of the C. elegans NaPi-III transporter, pitr-1, results in decreased brood size and dramatically increased expression of vitellogenin by the worm intestine. Unexpectedly, we found that the effects of pitr-1 mutation on vitellogenin expression in the intestine could only be rescued by expression of pitr-1 in the germline, and not by expression of pitr-1 in the intestine itself. Our results indicate the existence of a signal from the germline that regulates gene expression in the intestine, perhaps linking nutrient export from the intestine to production of gametes by the germline.

Somatic cell gene therapy for diabetes mellitus: engineering a surrogate B-cell

Improved methods of insulin delivery are required for the treatment of insulin-dependent diabetes mellitus (IDDM) to achieve a more physiological profile of glucose homeostasis. Somatic cell gene therapy offers the prospect that insulin could be delivered by an autologous cell implant, engineered to secrete insulin in response to glucose. This study explores the feasibility of manipulating somatic cells to behave as a surrogate insulin-secreting β-cells. Initial studies were conducted using mouse pituitary AtT20 cells as a model, since these cells possess an endogenous complement of enzymes capable of processing proinsulin to mature insulin. Glucose sensitive insulin secretion was conferred to these cells by transfection with plasmids containing the human preproinsulin gene (hppI-1) and the GLUT2 gene for the glucose transporter isoform 2. Insulin secretion was responsive to changes in the glucose concentration up to about 50μM. Further studies to up-rate this glucose sensitivity into the mM range will require manipulation of the hexokinase and glucokinase enzymes. Intraperitoneal implantation of the manipulated AtT20 cells into athymic nude mice with streptozotocin-induced diabetes resulted in decreased plasma glucose concentrations. The cells formed vascularised tumours in vivo which were shown to contain insulin-secreting cells. To achieve proinsulin processing in non-endocrine cells, co-transfection with a suitable enzyme, or mutagenesis of the proinsulin itself are necessary. The mutation of the human preproinsulin gene to the consensus sequence for cleavage by the subtilisin-like serine protease, furin, was carried out. Co-transfection of human fibroblasts with wild-type proinsulin and furin resulted in 58% conversion to mature insulin by these cells. Intraperitoneal implantation of the mature-insulin secreting human fibroblasts into the diabetic nude mouse animal model gave less encouraging results than the AtT20 cells, apparently due to poor vascularisation. Cell aggregations removed from the mice at autopsy were shown to contain insulin secreting cells only at the periphery. This thesis provides evidence that it is possible to construct, by cellular engineering, a glucose-sensitive insulin-secreting surrogate β-cell. Therefore, somatic cell gene therapy offers a feasible alternative for insulin delivery in IDDM patients.

Changes in gene expression and morphology of mouse embryonic stem cells on differentiation into insulin-producing cells in vitro and in vivo

Background Embryonic stem (ES) cells have the potential to produce unlimited numbers of surrogate insulin-producing cells for cell replacement therapy of type I diabetes mellitus. The impact of the in vivo environment on mouse ES cell differentiation towards insulin-producing cells was analysed morphologically after implantation. Methods ES cells differentiated in vitro into insulin-producing cells according to the Lumelsky protocol or a new four-stage differentiation protocol were analysed morphologically before and after implantation for gene expression by in situ reverse transcription polymerase chain reaction and protein expression by immunohistochemistry and ultrastructural analysis. Results In comparison with nestin positive ES cells developed according to the reference protocol, the number of ES cells differentiated with the four-stage protocol increased under in vivo conditions upon morphological analysis. The cells exhibited, in comparison to the in vitro situation, increased gene and protein expression of Pdx1, insulin, islet amyloid polypeptide (IAPP), the GLUT2 glucose transporter and glucokinase, which are functional markers for glucose-induced insulin secretion of pancreatic beta cells. Renal sub-capsular implantation of ES cells with a higher degree of differentiation achieved by in vitro differentiation with a four-stage protocol enabled further significant maturation for the beta-cell-specific markers, insulin and the co-stored IAPP as well as the glucose recognition structures. in contrast, further in vivo differentiation was not achieved with cells differentiated in vitro by the reference protocol. Conclusions A sufficient degree of in vitro differentiation is an essential prerequisite for further substantial maturation in a beta-cell-specific way in vivo, supported by cell-cell contacts and vascularisation. Copyright (c) 2009 John Wiley & Sons, Ltd.

Phytochemical mediated-modulation of the expression and transporter function of breast cancer resistance protein at the blood-brain barrier:an in-vitro study

Clinical translation of BCRP inhibitors have failed due to neurotoxicity and novel approaches are required to identify suitable modulators of BCRP to enhance CNS drug delivery. In this study we examine 18 compounds, primarily phytochemicals, as potential novel modulators of AhR-mediated regulation of BCRP expression and function in immortalised and primary porcine brain microvascular endothelial cells as a mechanism to enhance CNS drug delivery. The majority of modulators possessed a cellular viability IC50 > 100 µM in both cell systems. BCRP activity, when exposed to modulators for 1 hour, was diminished for most modulators through significant increases in H33342 accumulation at < 10 µM with 2,6,4-trimethoflavone increasing H33342 intracellular accumulation by 3.7–6.6 fold over 1–100 µM. Western blotting and qPCR identified two inducers of BCRP (quercetin and naringin) and two down-regulators (17-β-estradiol and curcumin) with associated changes in BCRP efflux transport function further confirmed in both cell lines. siRNA downregulation of AhR resulted in a 1.75 ± 0.08 fold change in BCRP expression, confirming the role of AhR in the regulation of BCRP. These findings establish the regulatory role AhR of in controlling BCRP expression at the BBB and confirm quercetin, naringin, 17-β-estradiol, and curcumin as novel inducers and down-regulators of BCRP gene, protein expression and functional transporter activity and hence potential novel target sites and candidates for enhancing CNS drug delivery.