NAD⁺-Dependent Enzyme SIRT3 Limits Intestinal Epithelial Cell Functions Through NAD⁺ Synthesis Pathway in Colorectal...

Area of Science:

• Immunology
• Cell Biology
• Gastroenterology

Background:

• Intestinal epithelial cells (IECs) are vital for mucosal immunity and barrier function.
• The precise mechanisms by which IECs regulate local immunity are not fully understood.

Purpose of the Study:

• To investigate the role of the NAD+-dependent enzyme SIRT3 in IECs.
• To elucidate the mechanisms by which SIRT3 influences T cell differentiation in colorectal cancer and colitis.

Main Methods:

• Studied the effects of IEC-specific SIRT3 overexpression and deficiency in models of colorectal cancer and colitis.
• Analyzed T cell differentiation (T_H1, CTLs) and cytokine production (IL-1β).
• Investigated the role of quinolinic acid (QA) and microbiota-derived metabolites in NAD+ synthesis and cellular function.

Main Results:

• IEC SIRT3 overexpression reduced IL-1β secretion and inhibited T_H1 and CTL differentiation.
• IEC SIRT3 deficiency enhanced IL-1β production and promoted T_H1 and CTL differentiation, limiting tumor growth but worsening colitis.
• SIRT3 deficiency utilized microbiota-derived QA for NAD+ synthesis, driving T cell responses via IL-1β-IL-1R1 signaling.

Conclusions:

• Microbiota-derived QA replenishes the NAD+ pool in IECs under SIRT3 deficiency, modulating T cell function.
• Targeting IEC SIRT3 and NAD+ metabolism offers potential therapeutic strategies for colorectal cancer and colitis.