Fatigue is one of the most common symptoms of Post COVID-19 Condition (PCC), yet it remains pathophysiologically and phenomenologically enigmatic. This article investigates the affective dimensions of PCC fatigue from within qualitative phe-nomenology and biomedicine, engaging in a non-reductionist dialogue across these strands. The article is comprised of a qualitative phenomenological analysis of lived experiences of fatigue in PCC; rehabilitation medicine (physician, physiotherapy, neuropsychology) assessments; brain MRI analysis; an analysis of inflammatory mediators in blood, and a cross-reading of results from these assessments and anal-yses, in relation to each other. The qualitative phenomenological analysis is fore-grounded, and identifies four affective modes: an affective mode in which patients wanted but had no capability or energy to engage with others and the world; a mode characterised by a lessened or lack of affective pull; a mode characterised by an assault-like feeling, and a mode characterized by a felt sense of "being in a bubble" or "being under water". The article sheds light on affective dimensions of PCC that are unlikely to be identified in everyday clinical practice, and the discussion across results from phenomenology and biomedical assessments and analyses brings out additional nuances in the understanding of the affective dimensions of fatigue

Several of the most debilitating symptoms in medi-cine, such as fatigue and pain, are highly non-specific and both difficult for the patient to describe and for the caregiver to interpret. The underlying factors con-tributing to such symptoms are often complex and multiple. Our purpose is to develop a cross-analysis methodology, developed from within an enactive in-terpretation of the biopsychosocial model that allows for a focus on neuroscientific, physiological, and expe-riential aspects of the person as a living being in their sociocultural world, and to do so in order to achieve a more holistic and clinically clarifying way of understan-ding complex conditions, such as post-COVID fatigue. Traditionally conceived, the biopsychosocial model of disease acknowledges this complexity, but does not as such suggest how to capture it for clinical or re-search purposes. In this paper, we propose a radically interdisciplinary approach, where experts from basic medical science, clinical medicine, psychology, pheno-menology, and ethics collaborate, each with their spe-cific perspectives and methods. We then combine and enrich the obtained results through a cross-analysis. We suggest that an enactively modernized biopsycho-social framework is especially suitable for this collabo-ration, as it acknowledges the close interrelation bet-ween mind, body, and environment, and can facilitate cross-analyses of data in this project.

Familial hypercholesterolemia (FH) is caused by mutations in the gene that encodes the low-density lipoprotein (LDL) receptor, which leads to an excessive increase in plasma LDL cholesterol levels. Previous studies have shown that FH is associated with gliosis, blood-brain barrier dysfunction, and memory impairment, but the mechanisms associated with these events are still not fully understood. Therefore, we aimed to investigate the role of microgliosis in the neurochemical and behavioral changes associated with FH using LDL receptor knockout (LDLr-/-) mice. We noticed that microgliosis was more severe in the hippocampus of middle-aged LDLr-/- mice, which was accompanied by microglial morphological changes and alterations in the immunocontent of synaptic protein markers. At three months of age, the LDLr(-/- )mice already showed increased microgliosis and decreased immunocontent of claudin-5 in the prefrontal cortex (PFC). Subsequently, 6-month-old male C57BL/6 wild-type and LDLr-/- mice were treated once daily for 30 days with minocycline (a pharmacological inhibitor of microglial cell reactivity) or vehicle (saline). Adult LDLr(-/- )mice displayed significant hippocampal memory impairment, which was ameliorated by minocycline treatment. Non-treated LDLr-/- mice showed increased microglial density in all hippocampal regions analyzed, a process that was not altered by minocycline treatment. Region-specific microglial morphological analysis revealed different effects of genotype or minocycline treatment on microglial morphology, depending on the hippocampal subregion analyzed. Moreover, 6-month-old LDLr-/- mice exhibited a slight but not significant increase in IBA-1 immunoreactivity in the PFC, which was reduced by minocycline treatment without altering microglial morphology. Minocycline treatment also reduced the presence of microglia within the perivascular area in both the PFC and hippocampus of LDLr-/- mice. However, no significant effects of either genotype or minocycline treatment were observed regarding the phagocytic activity of microglia in the PFC and hippocampus. Our results demonstrate that hippocampal microgliosis, microglial morphological changes, and the presence of these glial cells in the perivascular area, but not increased microglial phagocytic activity, are associated with cognitive deficits in a mouse model of FH.

Anorexia is a common symptom during infectious and inflammatory disease. Here we examined the role ofmelanocortin-4 receptors (MC4Rs) in inflammation-induced anorexia. Mice with transcriptional blockage of theMC4Rs displayed the same reduction of food intake following peripheral injection of lipopolysaccharide as wildtype mice but were protected against the anorexic effect of the immune challenge in a test in which fastedanimals were to use olfactory cues to find a hidden cookie. By using selective virus-mediated receptor reexpression we demonstrate that the suppression of the food-seeking behavior is subserved by MC4Rs in thebrain stem parabrachial nucleus, a central hub for interoceptive information involved in the regulation of foodintake. Furthermore, the selective expression of MC4R in the parabrachial nucleus also attenuated the bodyweight increase that characterizes MC4R KO mice. These data extend on the functions of the MC4Rs and showthat MC4Rs in the parabrachial nucleus are critically involved in the anorexic response to peripheral inflammation but also contribute to body weight homeostasis during normal conditions. 

Background: Vasomotor symptoms (VMS) are common around menopause. Menopausal hormone therapy is the most effective treatment for VMS. Physical exercise has been proposed as an alternative treatment since physically active women have previously been found to experience fewer VMS than inactive women. In our randomised controlled trial on resistance training to treat VMS, sympoms were reduced by 50% in the intervention group compared with the control group.

Objectives: To propose a mechanism to explain how resistance training reduced VMS and to assess if luteinizing hormone (LH) and follicle stimulating hormone (FSH) were affected in accordance with the proposed mechanism.

Trial design and methods: A substudy of a randomized controlled trial on 65 postmenopausal women with VMS and low physical activity who were randomised to 15 weeks of resistance training three times per week (n = 33) or to a control group (n = 32). To be regarded compliant to the intervention we predecided a mean of two training sessions per week. The daily number of VMS were registered before and during the 15 weeks. Blood samples were drawn for analysis of LH and FSH at baseline and after 15 weeks.

Results: LH decreased significantly in the compliant intervention group compared with the control group (-4.0±10.6 versus 2.9±9.0, p = 0.028 with Mann-Whitney U test). FSH also decreased in the compliant intervention group compared with the control group, however not enough to reach statistical significance (-3.5±16.3 versus 3.2±18.2, p = 0.063 with Mann-Whitney U test). As previously published the number of hot flushes decreased significantly more in the intervention group than in the control group but there was no association between change in LH or FSH and in number of VMS.

Conclusions: We propose that endogenous opiods such as β-endorphin or dynorphin produced during resistance training decreased VMS by stimulating KNDγ-neurons to release neurokinin B to the hypothalamic thermoregulatory centre. Through effects on KNDγ-neurons, β-endorphin could also inhibit GnRH and thereby decrease the production of LH and FSH. The significanty decreased LH in the compliant intervention group compared with the control group was in accordance with the proposed mechanism.

We examined the signaling route for fever during localized inflammation in male and female mice, elicited by casein injection into a preformed air pouch. The localized inflammation gave rise to high concentrations of prostaglandins of the E species (PGE(2)) and cytokines in the air pouch and elevated levels of these inflammatory mediators in plasma. There were also elevated levels of PGE(2) in the cerebrospinal fluid, although there was little evidence for PGE(2) synthesis in the brain. Global deletion of the PGE(2) prostaglandin E receptor 3 (EP3) abolished the febrile response as did deletion of the EP3 receptor in neural cells, whereas its deletion on peripheral nerves had no effect, implying that PGE(2) action on this receptor in the CNS elicited the fever. Global deletion of the interleukin-1 receptor type 1 (IL-1R1) also abolished the febrile response, whereas its deletion on neural cells or peripheral nerves had no effect. However, deletion of the IL-1R1 on brain endothelial cells, as well as deletion of the interleukin-6 receptor a on these cells, attenuated the febrile response. In contrast, deletion of the PGE(2) synthesizing enzymes cyclooxygenase-2 and microsomal prostaglandin synthase-1 in brain endothelial cells, known to attenuate fever evoked by systemic inflammation, had no effect. We conclude that fever during localized inflammation is not mediated by neural signaling from the inflamed site, as previously suggested, but is dependent on humoral signaling that involves interleukin actions on brain endothelial cells, probably facilitating PGE(2) entry into the brain from the circulation and hence representing a mechanism distinct from that at work during systemic inflammation.

Experimental autoimmune encephalomyelitis (EAE) is the most common model for studying the molecular mechanisms of multiple sclerosis (MS). Here, we examined the CNS-restricted effects of classical interleukin (IL)6 signaling on the development of EAE, using mice with cell-type specific deletion of the IL-6 receptor (IL-6R). We found that IL-6R deletion in CNS vascular endothelial cells, but not in microglia, ameliorated symptoms of EAE. The milder clinical symptoms in the gene-deleted mice were associated with less demyelination and immune cell infiltration/activation, and lower mRNA levels of the cytokines IL-17 and IL-1 beta, as well as the cell adhesion molecules VCAM-1, ICAM-1 and ICAM-2 than what was seen in WT mice. These findings demonstrate that classical IL-6 signaling via endothelial cells of the CNS contributes substantially to the development of MS-like pathology, which should be taken into consideration when conceptualizing future therapeutic approaches.

Maternal care is crucial for infants and profoundly affects their responses to different kinds of stressors. Here, we examined how maternal separation affects inflammatory gene expression and the corticosterone response to an acute immune challenge induced by lipopolysaccharide (LPS; 40 µg/kg ip) in mouse pups, 8–9 days old. Maternal separation initially attenuated LPS-induced hypothalamic pro-inflammatory gene expression, but later, at 3 h after immune challenge, robustly augmented such gene expression and increased serum corticosterone levels. Providing the pups with a warm and soft object prevented the separation-induced augmented hypothalamic-pituitary-adrenal (HPA)-axis response. It also prevented the potentiated induction of some, but not all, inflammatory genes to a similar extent as did the dam. Our results show that maternal separation potentiates the inflammatory response and the resulting HPA-axis activation, which may have detrimental effects if separation is prolonged or repeated.

Systemic inflammation elicits malaise and a negative affective state. The mechanism underpinning the aversive component of inflammation include cerebral prostaglandin synthesis and modulation of dopaminergic reward circuits, but the messengers that mediate the signaling between the peripheral inflammation and the brain have not been sufficiently characterized. Here we investigated the role of interferon-ɣ (IFN-ɣ) in the aversive response to systemic inflammation induced by a low dose (10μg/kg) of lipopolysaccharide (LPS) in mice. LPS induced IFN-ɣ expression in the blood and deletion of IFN-ɣ or its receptor prevented the development of conditioned place aversion to LPS. LPS induced expression of the chemokine Cxcl10 in the striatum of normal mice, but this induction was absent in mice lacking IFN-ɣ receptors or Myd88 in blood brain barrier endothelial cells. Furthermore, inflammation-induced aversion was blocked in mice lacking Cxcl10 or its receptor Cxcr3. Finally, mice with a selective deletion of the IFN-ɣ receptor in brain endothelial cells did not develop inflammation-induced aversion, demonstrating that the brain endothelium is the critical site of IFN-ɣ action. Collectively, these findings show that circulating IFN-ɣ that binds to receptors on brain endothelial cells and induces Cxcl10, is a central link in the signaling chain eliciting inflammation-induced aversion.

It is critical for survival to assign positive or negative valence to salient stimuli in a correct manner. Accordingly, harmful stimuli and internal states characterized by perturbed homeostasis are accompanied by discomfort, unease, and aversion. Aversive signaling causes extensive suffering during chronic diseases, including inflammatory conditions, cancer, and depression. Here, we investigated the role of melanocortin 4 receptors (MC4Rs) in aversive processing using genetically modified mice and a behavioral test in which mice avoid an environment that they have learned to associate with aversive stimuli. In normal mice, robust aversions were induced by systemic inflammation, nausea, pain, and. opioid receptorinduced dysphoria. In sharp contrast, mice lacking MC4Rs displayed preference or indifference toward the aversive stimuli. The unusual flip from aversion to reward in mice lacking MC4Rs was dopamine dependent and associated with a change from decreased to increased activity of the dopamine system. The responses to aversive stimuli were normalized when MC4Rs were reexpressed on dopamine D1 receptor-expressing cells or in the striatum of mice otherwise lacking MC4Rs. Furthermore, activation of arcuate nucleus proopiomelanocortin neurons projecting to the ventral striatum increased the activity of striatal neurons in an MC4R-dependent manner and elicited aversion. Our findings demonstrate that melanocortin signaling through striatal MC4Rs is critical for assigning negative motivational valence to harmful stimuli.