Valproic acid restricts mast cell activation by Listeria monocytogenes

Area of Science:

• Immunology
• Microbiology
• Pharmacology

Background:

• Mast cells (MC) are crucial for early bacterial infection control, particularly against Listeria monocytogenes (L.m).
• Valproic acid (VPA) has been shown to inhibit immune responses that may favor L.m pathogenesis.
• Understanding MC activation mechanisms by L.m is key to developing therapeutic strategies.

Purpose of the Study:

• To investigate the immunomodulatory effects of valproic acid (VPA) on Listeria monocytogenes-induced mast cell (MC) activation.
• To determine if VPA can inhibit MC degranulation and cytokine release triggered by L.m.
• To elucidate the signaling pathways affected by VPA during MC activation.

Main Methods:

• Bone marrow-derived mast cells (BMMC) were pre-incubated with VPA and then stimulated with L.m.
• MC degranulation and cytokine release were measured.
• Cell surface TLR2 expression was assessed.
• Activation of signaling cascades (Ca2+, p38, ERK1/2, NF-κB) was analyzed.

Main Results:

• VPA significantly reduced L.m-induced MC degranulation and cytokine release.
• VPA treatment did not alter MC TLR2 cell surface expression but inhibited activation by TLR2 ligands (peptidoglycan, Pam3CSK4).
• VPA decreased cytokine production in response to Listeriolysin O (LLO) and inhibited key signaling events including intracellular Ca2+ increase and phosphorylation of p38, ERK1/2, and NF-κB.

Conclusions:

• Valproic acid effectively modulates mast cell activation in response to Listeria monocytogenes infection.
• VPA impacts both TLR2-dependent and -independent pathways, as well as critical intracellular signaling cascades.
• These findings suggest VPA has the potential to modulate immune cell function in controlling L.m infection.