title: PCSK9 at the crossroad of cholesterol metabolism and immune function during infections.
abstract: Sepsis, a complex and dynamic syndrome resulting from microbial invasion and immune system dysregulation, is associated with an increased mortality, reaching up to 35% worldwide. Cholesterol metabolism is often disturbed during sepsis, with low plasma cholesterol levels being associated with poor prognosis. Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes degradation of the low-density lipoprotein receptor (LDLR), thus regulating intracellular and plasma cholesterol levels. PCSK9 is often upregulated during sepsis and might have a detrimental effect on immune host response and survival. Accordingly, PCSK9 reduces lipopolysaccharide uptake and clearance by human hepatocytes. Moreover, PCSK9 upregulation exacerbates organ dysfunction and tissue inflammation during sepsis, whereas a protective effect of PCSK9 deficiency has been documented in septic patients. Although a possible detrimental impact of PCSK9 on survival has been described, some beneficial effects of PCSK9 on immune response may be hypothesized. First, PCSK9 is associated with increased plasma cholesterol levels, which might be protective during sepsis. Second, PCSK9, by stimulating LDLR degradation and inhibiting reverse cholesterol transport (RCT), might promote preferential cholesterol accumulation in macrophages and other immune cells; these events might improve lipid raft composition and augment toll-like receptor function thus supporting inflammatory response. Hence, a more clear definition of the role of PCSK9 in septic states might provide additional insight in the understanding of the sepsis-associated immune dysregulation and enhance therapeutic outcomes.
authors.affiliation: Department of Medicine, Unit of Internal Medicine, University of Perugia, Perugia, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Paciullo
authors.affiliation: Department of Experimental Medicine, Unit of Pharmacology, University of Perugia, Perugia, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Fallarino
authors.affiliation: Department of Medicine, Unit of Internal Medicine, University of Perugia, Perugia, Italy.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Bianconi
authors.affiliation: Department of Medicine, Unit of Internal Medicine, University of Perugia, Perugia, Italy.
authors.forename: Massimo R
authors.initials: MR
authors.lastname: Mannarino
authors.affiliation: Biotechnology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Amirhossein
authors.initials: A
authors.lastname: Sahebkar
authors.affiliation: Department of Medicine, Unit of Internal Medicine, University of Perugia, Perugia, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Pirro
mesh_terms: D000818:Animals; D001419:Bacteria / Q000276:immunology / Q000378:metabolism / Q000472:pathogenicity*; D002784:Cholesterol / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D006801:Humans; D000071449:Proprotein Convertase 9 / Q000276:immunology / Q000378:metabolism*; D059748:Proteolysis; D011973:Receptors, LDL / Q000378:metabolism; D018805:Sepsis / Q000097:blood / Q000201:enzymology* / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology; D015398:Signal Transduction; D014777:Virus Diseases / Q000201:enzymology* / Q000453:epidemiology / Q000276:immunology / Q000821:virology; D014780:Viruses / Q000276:immunology / Q000378:metabolism / Q000472:pathogenicity*
chemical_list: D011973:Receptors, LDL; D002784:Cholesterol; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9
keywords: PCSK9; cholesterol; immune system; inflammation; sepsis