title: Sickness: From the focus on cytokines, prostaglandins, and complement factors to the perspectives of neurons.
abstract: Systemic inflammation leads to a variety of physiological (e.g. fever) and behavioral (e.g. anorexia, immobility, social withdrawal, depressed mood, disturbed sleep) responses that are collectively known as sickness. While these phenomena have been studied for the past few decades, the neurobiological mechanisms by which sickness occurs remain unclear. In this review, we first revisit how the body senses and responds to infections and injuries by eliciting systemic inflammation. Next, we focus on how peripheral inflammatory molecules such as cytokines, prostaglandins, and activated complement factors communicate with the brain to trigger neuroinflammation and sickness. Since depression also involves inflammation, we further elaborate on the interrelationship between sickness and depression. Finally, we discuss how immune activation can modulate neurons in the brain, and suggest future perspectives to help unravel how changes in neuronal functions relate to sickness responses.
authors.affiliation: Laboratory of Neurodegenerative Diseases, School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region.
authors.forename: David Chun-Hei
authors.initials: DC
authors.lastname: Poon
authors.affiliation: School of Nursing, Faculty of Health and Social Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong Special Administrative Region.
authors.forename: Yuen-Shan
authors.initials: YS
authors.lastname: Ho
authors.affiliation: Laboratory of Retina Brain Research, Department of Ophthalmology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region.
authors.forename: Kin
authors.initials: K
authors.lastname: Chiu
authors.affiliation: Laboratory of Neurodegenerative Diseases, School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region.
authors.forename: Hoi-Lam
authors.initials: HL
authors.lastname: Wong
authors.affiliation: Laboratory of Neurodegenerative Diseases, School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region; Research Centre of Heart, Brain, Hormone and Healthy Aging, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region; State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong Special Administrative Region. Electronic address: rccchang@hku.hk.
authors.forename: Raymond Chuen-Chung
authors.initials: RC
authors.lastname: Chang
mesh_terms: D001921:Brain / Q000276:immunology*; D003165:Complement System Proteins / Q000276:immunology*; D016207:Cytokines / Q000276:immunology*; D006801:Humans; D055809:Illness Behavior / Q000502:physiology*; D007249:Inflammation / Q000276:immunology*; D009474:Neurons / Q000276:immunology*; D011453:Prostaglandins / Q000276:immunology*
chemical_list: D016207:Cytokines; D011453:Prostaglandins; D003165:Complement System Proteins
keywords: Complement factors; Cytokines; Depression; Neurohormones; Neuroinflammation; Prostaglandins; Sickness response; Systemic inflammation