Heat Shock Protein 27 Immune Complex Altered Signaling and Transport (ICAST): Novel Mechanisms of Attenuating Inflammation

Blood levels of heat shock protein (HSP27) and natural IgG auto-antibodies to HSP27 (AAbs) are higher in healthy controls compared to cardiovascular disease patients. Vaccination of mice with recombinant HSP25 (rHSP25, murine ortholog of human rHSP27) increased AAb levels, attenuated atherogenesis and reduced plaque inflammation and cholesterol content. We sought to determine if the HSP27 immune complex (IC) altered MΦ inflammation signaling (Toll Like Receptor 4; TLR4), and scavenger receptors involved in cholesterol uptake (SR-AI, CD-36). Combining a validated polyclonal IgG anti-HSP27 antibody (PAb) with rHSP27 enhanced binding to THP-1 MΦ cell membranes and activation of NF-κB signaling via TLR4, competing away LPS and effecting an anti-inflammatory cytokine profile. Similarly, adding the PAb with rHSP27 enhanced binding to SR-AI and CD-36, as well as lowered oxLDL binding in HEK293 cells separately transfected with SR-AI and CD-36, or THP-1 MΦ. Finally, the PAb enhanced the uptake and internalization of rHSP27 in THP-1 MΦ. Thus, the HSP27 IC potentiates HSP27 cell membrane signaling with receptors involved in modulating inflammation and cholesterol uptake, as well as HSP27 internalization. Going forward, we will explore HSP27 Immune Complex Altered Signaling and Transport (ICAST) as a new anti-inflammatory therapeutic strategy in vivo.Competing Interest StatementEOB is the inventor on US Provisional Patent Application (serial number: 63/031,640). EOB is the Scientific Co-Founder of Pemi31 Therapeutics Inc., a startup company that controls the aforementioned intellectual property. EOB, CS and YXC have equity interests in Pemi31 Therapeutics Inc.Nonstandard AbbreviationsAAbanti-HSP27 (or anti-HSP25) antibodiesApoE-/-apolipoprotein E nulla.u.absorbance unitsBSAbovine serum albuminHSPheat shock proteinHSP27Heat Shock Protein 27IL-10interleukin-10IL-1βinterleukin-1 betaLDLlow density lipoprotein cholesterolLDLRlow density lipoprotein receptorNF-κBnuclear factor kappa light chain enhancer of activated B cellsONovernightoxLDLoxidized LDLPBSphosphate buffered salinePBSTPBS tweenrC1recombinant C-terminal truncation of HSP27 spanning amino acids 90-205rHSP27recombinant HSP27Strep-HRTstreptavidin-horse radish peroxidaseTLR-4toll-like receptor 4TMB3,3′,5,5′-tetramethylbenzidineView Full Text