Central daily regulation of splenic macrophage clock: Role of norepinephrine

CARGNELUTTI ETHELINA; CASTRO PASCUAL IVANNA; TOLEDO FERNANDA; ANZULOVICH ANA CECILIA

Congreso; XXXVIII Congreso Anual SAN 2023; 2023

The suprachiasmatic nucleus (SCN)functions as the central clock in mammals, synchronizing endogenous cellularclocks with the day/night alternation. Splenic macrophages (MΦ) play pivotal roles infundamental immune responses. However, a comprehensive understanding of thecentral circadian regulation of these cells remains elusive. The SCN and spleencommunicate through the sympathetic nervous system (SNS), that releasenorepinephrine (NE) in regions housing MΦ.To elucidate NE's influence on the molecular clock regulation of spleen MΦ, a rat model oflocalized sympathetic denervation was developed using guanethidine. Ratsreceived saline or guanethidine injections and were euthanized at 6 zeitgebertimes (ZT) across a 24-hour cycle (ZT2, 6, 10, 14, 18, and 22). Spleens were isolatedfor ex vivo cultures. BMAL1 and ACTIN protein levels were assessed insplenic adherent cells. Control rats' splenic MΦ displayed dailyoscillations of BMAL1, with a peak occurring at the midpoint of the lightperiod. Remarkably, ex vivo splenic MΦ from theguanethidine-treated animals showed a loss of the 24-hour BMAL1 oscillation andsignificantly lower levels, compared to controls. Both control andsympathectomized rats displayed daily Rev-Erbα expression rhythms.However, guanethidine administration induced a phase delay and increasedexpression of Rev-Erbα.These findings underscore the SCN-mediated regulation of the molecular clock insplenic adherent cells through the NE sympathetic pathway.