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Hepatocytes coordinate immune evasion in cancer via release of serum amyloid A proteins [HotvsCold]

ABSTRACT: To define changes in the liver that coordinate systemic inflammation and T cell surveillance, we performed RNA sequencing on livers of mice with T cellhigh and T celllow tumors.

ORGANISM(S): Mus musculus

PROVIDER: GSE232260 | GEO | 2024/03/13

REPOSITORIES: GEO

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Project description:BACKGROUND:Acute-phase response is a systemic reaction to environmental/inflammatory insults and involves production of acute-phase proteins, including serum amyloid A (SAA). Interleukin-1? (IL-1?), a master regulator of neuroinflammation produced by activated inflammatory cells of the myeloid lineage, in particular microglia, plays a key role in the pathogenesis of acute and chronic diseases of the peripheral nervous system and CNS. IL-1? release is promoted by ATP acting at the purinergic P2X7 receptor (P2X7R) in cells primed with toll-like receptor (TLR) ligands. METHODS:Purified (>?99%) microglia cultured from neonatal rat cortex and cerebellum were first primed with the putative TLR4/TLR2 agonist SAA (recombinant human Apo-SAA) or the established TLR4 agonist lipopolysaccharide (LPS) followed by addition of ATP. Expression of genes for the NLRP3 inflammasome, IL-1?, tumor necrosis factor-? (TNF-?), and SAA1 was measured by quantitative real-time polymerase chain reaction (q-PCR). Intracellular and extracellular amounts of IL-1? were determined by ELISA. RESULTS:Apo-SAA stimulated, in a time-dependent manner, the expression of NLRP3, IL-1?, and TNF-? in cortical microglia, and produced a concentration-dependent increase in the intracellular content of IL-1? in these cells. A 2-h 'priming' of the microglia with Apo-SAA followed by addition of ATP for 1 h, resulting in a robust release of IL-1? into the culture medium, with a concomitant reduction in its intracellular content. The selective P2X7R antagonist A740003 blocked ATP-dependent release of IL-1?. Microglia prepared from rat cerebellum displayed similar behaviors. As with LPS, Apo-SAA upregulated SAA1 and TLR2 mRNA, and downregulated that of TLR4. LPS was less efficacious than Apo-SAA, perhaps reflecting an action of the latter at TLR4 and TLR2. The TLR4 antagonist CLI-095 fully blocked the action of LPS, but only partially that of Apo-SAA. Although the TLR2 antagonist CU-CPT22 was inactive against Apo-SAA, it also failed to block the TLR2 agonist Pam3CSK4. CONCLUSIONS:Microglia are central to the inflammatory process and a major source of IL-1? when activated. P2X7R-triggered IL-1? maturation and export is thus likely to represent an important contributor to this cytokine pool. Given that SAA is detected in Alzheimer disease and multiple sclerosis brain, together with IL-1?-immunopositive microglia, these findings propose a link between P2X7R, SAA, and IL-1? in CNS pathophysiology.

Project description:Serum amyloid A (SAA) proteins are one of the most inducible acute-phase reactants and are precursors of secondary amyloidosis. In the mouse, SAA1 and SAA2 are induced in approximately equal quantities in response to amyloid induction models. These two isotypes differ in only 9 of 103 amino acid residues; however, only SAA2 is selectively deposited into amyloid fibrils. SAA expression in the CE/J mouse species is an exception in that gene duplication did not occur and the CE/J variant is a hybrid molecule sharing features of SAA1 and SAA2. However, even though it is more closely related to SAA2 it is not deposited as amyloid fibrils. We have developed an adenoviral vector system to overexpress SAA proteins in cell culture to determine the ability of these proteins to form amyloid fibrils, and to study the structural features in relation to amyloid formation. Both the SAA2 and CE/J SAA proteins were synthesized in large quantities and purified to homogeneity. Electron microscopic analysis of the SAA proteins revealed that the SAA2 protein was capable of forming amyloid fibrils, whereas the CE/J SAA was incapable. Radiolabelled SAAs were associated with normal or acute-phase high-density lipoproteins (HDLs); we examined them for their clearance from the circulation. In normal mice, SAA2 had a half-life of 70 min and CE/J SAA had a half-life of 120 min; however, in amyloid mice 50% of the SAA2 cleared in 55 min, compared with 135 min for the CE/J protein. When the SAA proteins were associated with acute-phase HDLs, SAA2 clearance was decreased to 60 min in normal mice compared with 30 min in amyloidogenic mice. Both normal and acute-phase HDLs were capable of depositing SAA2 into preformed amyloid fibrils, whereas the CE/J protein did not become associated with amyloid fibrils. This established approach opens the doors for large-scale SAA production and for the examination of specific amino acids involved in the fibrillogenic capability of the SAA2 molecule in vitro and in vivo.

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Hepatocytes coordinate immune evasion in cancer via release of serum amyloid A proteins [HotvsCold]

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