Cutting edge: hemokinin has substance P-like function and expression in inflammation

Area of Science:

• Immunology
• Neuroscience
• Molecular Biology

Background:

• Substance P (SP) is a neuropeptide and proinflammatory mediator belonging to the tachykinin family.
• SP binds to the neurokinin 1 receptor (NK-1R) on various cells, influencing inflammatory responses.
• Hemokinin (HK), another tachykinin, originates from a distinct precursor (preprotachykinin C) and also interacts with NK-1R.

Purpose of the Study:

• To investigate the functional role of Hemokinin (HK) at inflammatory sites.
• To determine if HK exhibits similar functions to Substance P (SP) in the context of inflammation.
• To elucidate the shared mechanisms of tachykinins in governing chronic inflammation.

Main Methods:

• Detection of preprotachykinin C mRNA in murine schistosome granulomas and intestinal mononuclear cells.
• Assessment of HK binding to NK-1R on T cells and macrophages within granulomas.
• Measurement of IFN-gamma production stimulated by SP and HK, and the effect of NK-1R antagonists.

Main Results:

• Preprotachykinin C mRNA was found in granulomas and intestinal immune cells, including T cells and macrophages.
• HK demonstrated high-affinity binding to NK-1R on granuloma T cells.
• Both SP and HK stimulated IFN-gamma production with comparable potency, an effect blocked by an NK-1R antagonist.

Conclusions:

• Hemokinin (HK) and Substance P (SP) are co-expressed at chronic inflammatory sites.
• HK and SP share the same receptor (NK-1R) and exhibit similar immunoregulatory functions, particularly in IFN-gamma secretion.
• Two distinct tachykinins, HK and SP, cooperatively regulate inflammation via NK-1R signaling.