Dhaksshaginy Rajalingam

• Rajalingam, Dhaksshaginy; Boix, Fernando; Khoder, Ala Zaim; Andersen, Jannike Mørch & Paulsen, Ragnhild Elisabeth Heimtun (2023). Distribution of morphine and methadone to the brain in a developmental chicken embryo model. Toxicology and Applied Pharmacology. ISSN 0041-008X. 479. doi: 10.1016/j.taap.2023.116731. Fulltekst i vitenarkiv Vis sammendrag

  The use and/or misuse of opioids by pregnant women would expose the fetuses to these drugs during critical stages of development with serious effects for the newborn, like the neonatal abstinence syndrome (NAS). We have revisited an established chicken model for NAS to describe the distribution of morphine and methadone to the brain and explore its validity as a valuable alternative to rodent models. For this purpose, chicken eggs were injected with a single dose of 10 mg/kg or 20 mg/kg morphine or 20 mg/kg methadone onto the chorioallantoic membrane (CAM) on embryonal day 13. Whole brains and lungs were harvested and the concentrations of morphine, methadone and their subsequent metabolites (morphine-3-glucuronide and EDDP, respectively) determined in the brain and lungs at different time points using LC-MS/MS. Morphine and methadone, as well as their metabolites, were detected both in the brain and lungs, with significantly higher concentrations in the lungs. Pharmacokinetic modelling showed that the distribution of morphine to the brain followed a first-order absorption with transit compartments and linear elimination, with concentrations linearly dependent on dose. Moreover, methadone, but not morphine, reduced μ receptor (the main morphine receptor) binding, which can be of relevance for opioid tolerance. The present study is the first to report the brain distribution of morphine, which can be described by standard pharmacokinetic processes, and methadone in the developing chicken embryo. The present findings supplement the already established model and support the use of this chicken model to study NAS.

• Rajalingam, Dhaksshaginy; Nymoen, Ingeborg; Nyberg, Henriette; Nielsen, Morten Birkeland; Einarsen, Ståle Valvatne & Gjerstad, Johannes (2021). Workplace bullying increases the risk of anxiety through a stress-induced β2-adrenergic receptor mechanism: a multisource study employing an animal model, cell culture experiments and human data. International Archives of Occupational and Environmental Health. ISSN 0340-0131. 94, s. 1905–1915. doi: 10.1007/s00420-021-01718-7. Fulltekst i vitenarkiv Vis sammendrag

  Objectives Several studies show that severe social stressors, e.g., in the form of exposure to workplace bullying in humans, is associated with negative mental health effects such as depression and anxiety among those targeted. However, the understanding of the underlying biological mechanisms that may explain the relationship between exposure to bullying and such negative health outcomes is scarce. The analyses presented here focus on understanding the role of the β2-adrenergic receptors (ADRB2) on this association. Methods First, a resident-intruder paradigm was used to investigate changes in circulating norepinephrine (NE) in rat serum induced by repeated social defeat and its relationship with subsequent social behavior. Second, the direct effects of the stress-hormones NE and cortisol, i.e., synthetic dexamethasone (DEX), on the ADRB2 expression (qPCR) and monocyte chemoattractant protein-1 (MCP-1) release (immunoassay) was examined in cultured EL-1 cells. Third, in a probability sample of 1052 Norwegian employees, the 9-item short version of the Negative Acts Questionnaire—Revised (S-NAQ) inventory, Hopkins Symptom Checklist and genotyping (SNP TaqMan assay) were used to examine the association between social stress in the form of workplace bullying and anxiety moderated by the ADRB2 genotype (rs1042714) in humans. Results The present study showed a clear association between reduced social interaction and increased level of circulating NE in rats previously exposed to repeated social defeat. Parallel cell culture work, which was performed to examine the direct effects of NE and DEX on ADRB2, demonstrated ADRB2 downregulation and MCP-1 upregulation in cultured EL-1 cells. Genotyping with regard to the ADRB2 genotype; rs1042714 CC vs CG/GG, on human saliva samples, showed that individuals with CC reported more anxiety following exposure to bullying behaviors as compared to the G carriers. Conclusion We conclude that workplace bullying promotes anxiety and threaten well-being through an ADRB2 associated mechanism.

• Nielsen, Morten Birkeland; Pallesen, Ståle; Einarsen, Ståle; Harris, Anette; Rajalingam, Dhaksshaginy & Gjerstad, Johannes (2021). Associations between exposure to workplace bullying and insomnia. A cross-lagged prospective study of causal directions. International Archives of Occupational and Environmental Health. ISSN 0340-0131. 94, s. 1003–1011. doi: 10.1007/s00420-020-01618-2. Fulltekst i vitenarkiv Vis sammendrag

  Objective Workplace bullying has been established as a significant correlate of sleep problems. However, little is known regarding the causal direction between bullying and sleep. The aim of this study was to examine temporal relationships between bullying and symptoms of insomnia. Methods Reciprocal and prospective associations between exposure to workplace bullying and symptoms of insomnia were investigated in a national probability sample comprising 1149 Norwegian employees. Data stemmed from a two-wave full panel survey study with a 6-month time interval between the baseline and follow-up assessments. Models with stabilities, forward-, reverse-, and reciprocal associations were tested and compared using Structural Equation Modelling. Analyses were adjusted for age, gender, and the stability in the outcome variables over time. Workplace bullying was assessed with the nine-item Short Negative Acts Questionnaire. Insomnia was assessed with a previously validated three item scale reflecting problems with sleep onset, sleep maintenance, and early morning awakening. Results The forward association model, which showed that exposure to workplace bullying prospectively increased levels of insomnia (b = 0.08; p < 0.001), had best fit with the data [CFI = 0.94; TLI = 0.93; RMSEA = 0.049 (0.046–0.052)]. The reverse association model where insomnia influences risk of being subjected to bullying was not supported. Conclusion Workplace bullying is a risk factor for later insomnia. There is a need for further studies on moderating and mediating variables that can explain how and when bullying influence sleep.

• Rajalingam, Dhaksshaginy; Nymoen, Ingeborg; Jacobsen, Daniel Pitz; Eriksen, Mina Baarnes; Dissen, Erik & Nielsen, Morten Birkeland [Vis alle 8 forfattere av denne artikkelen] (2020). Repeated social defeat promotes persistent inflammatory changes in splenic myeloid cells; decreased expression of β-arrestin-2 (ARRB2) and increased expression of interleukin-6 (IL-6). BMC Neuroscience. 21:25. doi: 10.1186/s12868-020-00574-4. Fulltekst i vitenarkiv Vis sammendrag

  Background Previous studies suggest that persistent exposure to social stress in mammals may be associated with multiple physiological effects. Here, we examine the effects of social stress in rats, i.e. repeated social defeat, on behavior, hypothalamic–pituitary–adrenal (HPA)-axis and immune system. Methods A resident-intruder paradigm, where an intruder rat was exposed to social stress by a dominant resident rat for 1 hour each day for 7 consecutive days was used. The day after the last stress exposure in the paradigm the data were analyzed. Variation in social interaction was observed manually, whereas locomotion was analyzed off-line by a purpose-made software. Gene expression in the pituitary gland, adrenal gland and myeloid cells isolated from the spleen was measured by qPCR. Results The exposure to social stress induced decreased weight gain and increased locomotion. An increased nuclear receptor subfamily group C number 1 (NR3C1) expression in the pituitary gland was also shown. In myeloid cells harvested from the spleen, we observed decreased expression of the β2-adrenergic receptor (ADRB2) and β-arrestin-2 (ARRB2), but increased expression of interleukin-6 (IL-6). Subsequent analyses in the same cells showed that ARRB2 was negatively correlated with IL-6 following the stress exposure. Conclusion Our results show that that the experience of social stress in the form of repeated social defeat in rats is a potent stressor that in myeloid cells in the spleen promotes persistent inflammatory changes. Future research is needed to examine whether similar inflammatory changes also can explain the impact of social stress, such as bullying and harassment, among humans.

• Rajalingam, Dhaksshaginy; Jacobsen, Daniel Pitz; Nielsen, Morten Birkeland; Einarsen, Ståle & Gjerstad, Johannes (2019). Exposure to workplace bullying, distress, and insomnia: The moderating role of the miR-146a genotype. Frontiers in Psychology. 10:1204(MAY), s. 1–7. doi: 10.3389/fpsyg.2019.01204. Fulltekst i vitenarkiv Vis sammendrag

  Several lines of evidence show that systematic exposure to negative social acts at the workplace i.e., workplace bullying, results in symptoms of depression and anxiety among those targeted. However, little is known about the association between bullying, inflammatory genes and sleep problems. In the present study, we examined the indirect association between exposure to negative social acts and sleep through distress, as moderated by the miR-146a genotype. The study was based on a nationally representative survey of 1179 Norwegian employees drawn from the Norwegian Central Employee Register by Statistics Norway. Exposure to workplace bullying was measured with the 9-item version of Negative Acts Questionnaire – Revised (NAQ-R) inventory. Seventeen items from Hopkins Symptom Checklist (HSCL-25) was used to measure distress. Insomnia was assessed with three items reflecting problems with sleep onset, maintenance of sleep and early morning awakening. Genotyping with regard to miR146a rs2910164, previously linked to inflammatory processes, was carried out using Taqman assay. The data revealed that individuals systematically exposed to negative social acts at the workplace reported higher levels of sleep problems than non-exposed individuals. Moreover, the relationship between distress induced by exposure to negative social acts and insomnia was significantly stronger for individuals with the miR-146a GG genotype. Thus, the miR-146a genotype moderated the association between distress and insomnia among individuals exposed to negative social acts. The present report support the hypothesis that inflammation could play a role in stress-induced insomnia among individuals exposed to workplace bullying.

• Jacobsen, Daniel Pitz; Eriksen, Mina Baarnes; Rajalingam, Dhaksshaginy; Nymoen, Ingeborg; Nielsen, Morten Birkeland & Einarsen, Ståle [Vis alle 7 forfattere av denne artikkelen] (2019). Exposure to workplace bullying, microRNAs and pain; evidence of a moderating effect of miR-30c rs928508 and miR-223 rs3848900. Stress. ISSN 1025-3890. 23(1), s. 77–86. doi: 10.1080/10253890.2019.1642320. Fulltekst i vitenarkiv Vis sammendrag

  Prolonged exposure to bullying behaviors may give rise to symptoms such as anxiety, depression and chronic pain. Earlier data suggest that these symptoms often are associated with stress-induced low-grade systemic inflammation. Here, using data from both animals and humans, we examined the moderating role of microRNAs (miRNAs, miRs) in this process. In the present study, a resident-intruder paradigm, blood samples, tissue harvesting and subsequent qPCR analyses were used to screen for stress-induced changes in circulating miRNAs in rats. The negative acts questionnaire (NAQ), TaqMan assays and a numeric rating scale (NRS) for pain intensity were then used to examine the associations among bullying behaviors, relevant miRNA polymorphisms and pain in a probability sample of 996 Norwegian employees. In rats, inhibited weight gain, reduced pituitary POMC expression, adrenal Nr3c1 mRNA downregulation, as well as increased miR-146a, miR-30c and miR-223 in plasma were observed following 1 week of repeated exposure to social stress. When following up the miRNA findings from the animal study in the human working population, a stronger relationship between NAQ and NRS scores was observed in subjects with the miR-30c GG genotype (rs928508) compared to other subjects. A stronger relationship between NAQ and NRS scores was also seen in men with the miR-223 G genotype (rs3848900) as compared to other men. Our findings show that social stress may induce many physiological changes including changed expression of miRNAs. We conclude that the miR-30c GG genotype in men and women, and the miR-223 G genotype in men, amplify the association between exposure to bullying behaviors and pain.

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• Rajalingam, Dhaksshaginy; Gjerstad, Johannes & Nielsen, Morten Birkeland (2020). The impact of workplace bullying and repeated social defeat on health and behavioral outcomes: A biopsychosocial perspective. Universitetet i Bergen. ISSN 9788230866467. Fulltekst i vitenarkiv Vis sammendrag

  Workplace bullying is a severe problem that needs further investigation from a range of disciplines. Yet, during more than twenty years of research on workplace bullying, few studies have addressed the bullying phenomenon from a biological perspective. Hence, the purpose of this thesis was to learn more about how stressors such as workplace bullying in humans and repeated social defeat in rats affect the physiological and psychological mechanisms of the body, seeing the latter as an animal model of bullying among humans. The purpose of this thesis was, therefore, to advance our understanding of how workplace bullying leads to severe health problems in those targeted. As such, the present research addresses individual susceptibility when exposed to workplace bullying and examines causative effects and mechanisms on the relationship between exposure to workplace bullying and subsequent health outcomes. The first paper addressed the potential moderating effect of the miR-146a genotype on the association between exposure to workplace bullying and insomnia through psychological distress, using a nationally representative survey of Norwegian employees. The findings showed that the relationship between distress and insomnia induced by exposure to bullying was stronger among GG genotype individuals compared with GC/CC genotype individuals. The second paper addressed the neuro-immune changes initiated by exposure to prolonged social stressors. Thus, an animal model of repeated social defeat – the resident-intruder paradigm – was implemented. The animal data demonstrated stress-induced health effects, including reduced weight gain, hypothalamic-pituitary-adrenal (HPA) axis changes, and an increased inflammatory profile of the isolated splenic myeloid cells. The third paper addressed the changed expression of the β2-adrenergic receptor (ADRB2) during prolonged exposure to stressors and its role in the association between exposure to workplace bullying and anxiety. A moderating effect of the ADRB2 genotype on the workplace bullying-anxiety relationship in humans was also observed. Moreover, in vivo and in vitro experiments demonstrated reduced ADRB2 gene expression induced by the stress hormone norepinephrine (NE) and a stress-induced switch from an anti-inflammatory to a pro-inflammatory state of the immune cells. In conclusion, the findings of the present thesis indicate that persistent social stressors in the form of workplace bullying may lead to subjective health complaints such as insomnia and anxiety by promoting a state of low-grade systemic inflammation. Also, the findings from the animal model of repeated social defeat suggest that the systemic inflammation may be a consequence of the missing functioning of the “breaks” of the sympathetic nervous system (SNS) and HPA axis. The persistent inflammatory state following exposure to persistent social stressors, causing excess production of pro-inflammatory cytokines, seems to cause dysregulation and mal-adaptation of biological mechanisms central in the stress response system leading to physiological and psychological changes that may be damaging for overall health and well-being. Thus, the present thesis demonstrates a clear link between exposure to persistent social stressors, genetic factors, and severe health problems in targets of bullying.

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