Hunger-promoting hypothalamic neurons modulate effector and regulatory T-cell responses

Area of Science:

• Neuroendocrinology
• Immunology
• Metabolism

Background:

• The hypothalamus regulates whole-body energy metabolism, influencing various tissue functions.
• Agouti-related peptide (AgRP)-expressing neurons in the hypothalamus are key players in sensing energy status.

Purpose of the Study:

• To investigate the role of Sirtuin 1 (Sirt1) in hypothalamic AgRP neurons in regulating adaptive immunity.
• To determine the impact of altered hypothalamic energy sensing on T-cell activation and autoimmune responses.

Main Methods:

• Selective knockdown of Sirtuin 1 (Sirt1) in hypothalamic AgRP neurons in mice.
• Assessment of CD4(+) T-cell activation, cytokine production (Th1, Th17), and sympathetic nervous system activity.
• Analysis of thymic regulatory T cell (Treg) generation and peripheral suppressive capacity.
• Evaluation of delayed-type hypersensitivity responses and autoimmune disease susceptibility.

Main Results:

• Knockdown of Sirt1 in hypothalamic AgRP neurons reduced responsiveness to low energy signals.
• This manipulation significantly promoted CD4(+) T-cell activation and pro-inflammatory cytokine production.
• Impaired thymic generation and peripheral function of naturally occurring regulatory T cells (FoxP3+ Tregs) were observed.
• Increased delayed-type hypersensitivity and heightened autoimmune disease susceptibility in mice.

Conclusions:

• Hypothalamic Sirt1 in AgRP neurons plays a critical role in modulating adaptive immune responses.
• Altered hypothalamic energy metabolism signaling can dysregulate T-cell immunity and promote autoimmunity.
• Feeding circuits in the hypothalamus are unexpectedly involved in regulating adaptive immunity.