Change in light-dark cycle affects experimental autoimmune encephalomyelitis.

Area of Science:

• Neuroimmunology
• Chronobiology
• Autoimmune Diseases

Background:

• Multiple sclerosis prevalence correlates with geographic latitude, suggesting environmental factors like sunlight exposure play a role.
• Reduced daylight hours are hypothesized to influence the susceptibility and progression of autoimmune conditions.
• Experimental autoimmune encephalomyelitis (EAE) serves as a model to study autoimmune diseases affecting the central nervous system.

Purpose of the Study:

• To investigate the effect of altered photoperiods on the progression of experimental autoimmune encephalomyelitis (EAE).
• To determine if changes in daylight hours influence internal corticosterone secretion and its impact on EAE.
• To explore the potential immunosuppressive role of upregulated corticosterone in autoimmune disease.

Main Methods:

• Mice were housed in environments with a 24-hour light cycle, a 24-hour dark cycle, or a conventional 12-hour light/12-hour dark cycle.
• Experimental autoimmune encephalomyelitis (EAE) was induced in the mice.
• Corticosterone secretion levels and the rhythmic patterns were monitored throughout the study.
• Disease progression in EAE mice under different lighting conditions was assessed and compared.

Main Results:

• Mice housed in constant light or dark conditions exhibited upregulated internal corticosterone secretion compared to those in a 12/12-hour cycle.
• Upregulated corticosterone secretion was associated with amelioration of the EAE disease course.
• The rhythmic pattern of corticosterone secretion was disrupted following EAE induction.
• Constant photoperiods led to improved outcomes in the EAE model.

Conclusions:

• Altering daylight hours by housing mice in constant light or dark cycles can upregulate corticosterone secretion.
• Upregulated corticosterone, potentially through its immunosuppressive properties, can ameliorate the course of experimental autoimmune encephalomyelitis.
• Photoperiods represent a significant environmental factor influencing the neuroimmune axis and autoimmune disease progression.