Role of Non-feminizing Estrogens in Brain Protection from Cerebral Ischemia and Alzheimer ’ s Disease Neuropathology

Aims Atherosclerosis is a paradigmatic age-related disease that starts early but becomes clinically manifest later in life. Heat shock proteins (HSPs) are important antigens and autoantigens triggering innate and adaptive immune responses initiating the earliest still reversible inflammatory stages of atherosclerosis. We examined the immunological effect of mycobacterial HSP65 (mbHSP65) immunizations, oral mbHSP65-tolerization, and specific atheroprotective and atherogenic reactive T-cell mbHSP65-peptides, in C57BL/6J and ApoE mice. Methods and Results Mice received 4 mbHSP65 immunizations and/or 8 oral mbHSP65 feedings. Concomitantly with the first immunization/tolerization, mice were either kept on chow diet or high cholesterol diet. The aorta was analysed en face, immunohistologically, and for cytokine production, lymph node and spleen cells were examined for mbHSP65-specific T regulatory cells (Treg) and T-cell reactive mbHSP65-peptides, plasma/sera for lipids, cytokines, and anti-HSPs autoantibodies. We found significantly increased aortal lesion formation after mbHSP65 immunizations and abrogated lesion formation after oral mbHSP65 tolerization even in mbHSP65-immunized mice. The decreased lesion size was accompanied by decreased lipid levels, increased numbers and suppressive capacity of specific and non-specific Tregs, decreased amounts of proinflammatoryand increased amounts of anti-inflammatory cytokines in the aortae, intralesional cells, and circulation. Increased levels of anti-mbHSP65 and anti-mouse-HSP60 antibodies were found after mbHSP65 immunization/tolerization indicating specific (cross)-reactive immunity. Importantly, this study also provides functional proof for the presence of specific Tcell reactive mbHSP65-peptides in early stages of atherosclerosis, and after immunizations with these peptides, we could define their atheroprotective/atherogenic properties. Conclusions Our results demonstrate that oral mbHSP65-tolerization reduces the inflammatory process associated with mbHSP65-induced atherosclerosis and provides new immunological approaches for the treatment of atherosclerosis with specific atherogenic mbHSP65-peptides.