Accumulated evidence indicates that the circadian clock exists and functions in many peripheral tissues, including immune tissues and cells, though the details of the nature of the immune clocks and their relationship to central clock in the suprachiasmatic nucleus (SCN) is not well understood. Following our recent discovery of circadian expression of circadian clock genes, per1-3, in human and mPer1 and interlukine-2 (mIL-2) in mouse peripheral blood mononuclear cells, we hypothesize that 1) the circadian clock genes will prove to be important to immune functioning in health and disease. and 2) the clock regulatory mechanism in immune cells is regulated in part by SCN central clock through circadian signaling molecules, but functions as cell autonomous in certain extent. The proposed study is to test these hypotheses and provides insights into feature of immune clock system and brain-immune clock interactions.
The Specific Aims of this application are:
1. To investigate if there is autonomous immune clock by using in vivo approach. We will identify the defects in clock genes by comparing profiles of clock genes in immune tissues or cell from both wild-type and mPer1-/-/mPer2-/- double mutant strains, respectively. Then, these profiles will be used to compare with the ones derived from one strain of tissue-specific mutant mice, which is generated from bone marrow transplantation and carries with normal immune clock but mutated SCN clock (SCN-mPer1 -/-/mPer2-/-). If the restoration of rhythmicity of circadian clock genes in SCN-mPer1-/-/mPer2-/- were observed, it would suggest the autonomy of immune clock.
2. To elucidate the role of circadian clock in immune T cell function. We will measure the profiles of several immune regulatory genes, such as IL-2, TNFa, IL-12, INF-r, and IL-4 in different mouse strains which are under both constant darkness and dark/light cycle. Because we have collected the serum from mouse blood, the profile of cytokine (IL-1b, TNFa, IN-12, IL-4) will also been measured. The alteration of phase and amplitude in any one of immune regulatory genes would indicate a role of the circadian clock genes in regulating immune functioning. We will transplant BM cells from the mper1-/-/mper2-/- KO mice into normal mice to generate an Immune-mPer1-/-/mPer2-/- mutant mice to see if the observed oscillation of immune regulatory genes in wild-type mice is resulted from immune clock in the immune cells/tissues only or from the signals generated from SCN clock. Finally, we will employ in vitro approach to further identify how the clock genes regulate immune T cell functions, such as their ability to proliferate in response to mitogenic stimulation, to produce cytokines, and to differentiate into effector cells (Type I and Type II) under the influence of cytokines (IL-12 and IL-4).
The proposed studies, which will be conducted jointly as a cooperative venture by a molecular neurobiological laboratory and immunological laboratories, will extend our knowledge of immune clocks and their impact on immune physiology.