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The neuropeptide alpha-MSH has specific receptors on neutrophils and reduces chemotaxis in vitro
Abstract:
The proopiomelanocortin-derived peptide alpha-melanocyte stimulating hormone (alpha-MSH) has potent anti-inflammatory effects in all animal models of inflammation against which it has been tested. Understanding of the mechanism by which this occurs is incomplete, although there is recent evidence for alpha-MSH receptors in murine and human macrophages and for modulation of production of proinflammatory cytokines and related mediators by alpha-MSH. Because of the prominence of neutrophils in early stages of inflammatory reactions where alpha-MSH is effective, we examined human neutrophils for evidence of mRNA for alpha-MSH receptors and for inhibition of neutrophil chemotaxis. There was accumulation of mRNA for melanocortin receptor 1 (MC1) in RT/PCR product from neutrophils stimulated with interferon and LPS. In subsequent studies alpha-MSH inhibited migration of neutrophils from most normal volunteers when the cells were placed in FMLP or IL-8 gradients. The inhibition by alpha-MSH could be traced to alterations in cAMP in neutrophils. The presence of alpha-MSH receptor message in neutrophils is consistent with the established anti-inflammatory effects of the peptide. Direct inhibition of neutrophil chemotaxis likely contributes to the anti-inflammatory activity of alpha-MSH.
Insights
Alpha-melanocyte stimulating hormone (alpha-MSH) demonstrates anti-inflammatory effects by inhibiting neutrophil migration. This peptide targets melanocortin receptor 1 (MC1) on neutrophils, impacting inflammatory responses.
Area of Science:
- Immunology
- Endocrinology
- Molecular Biology
Background:
- Alpha-melanocyte stimulating hormone (alpha-MSH), a peptide derived from proopiomelanocortin, exhibits significant anti-inflammatory properties.
- Evidence suggests alpha-MSH receptors are present in macrophages, modulating pro-inflammatory cytokine production.
- Neutrophils are key players in early inflammatory stages where alpha-MSH shows efficacy.
Purpose of the Study:
- To investigate the presence of alpha-MSH receptors in human neutrophils.
- To determine if alpha-MSH can inhibit neutrophil chemotaxis.
- To elucidate the mechanism underlying alpha-MSH's anti-inflammatory effects on neutrophils.
Main Methods:
- Reverse transcription-polymerase chain reaction (RT/PCR) was used to detect mRNA for melanocortin receptor 1 (MC1) in human neutrophils.
- Neutrophil chemotaxis assays were performed using FMLP or IL-8 gradients.
- Changes in intracellular cyclic adenosine monophosphate (cAMP) levels were measured.
Main Results:
- mRNA for melanocortin receptor 1 (MC1) was detected in human neutrophils stimulated with interferon and LPS.
- Alpha-MSH significantly inhibited the migration of neutrophils from most normal volunteers.
- The inhibitory effect of alpha-MSH on neutrophil migration was associated with alterations in cAMP levels.
Conclusions:
- Human neutrophils express mRNA for the alpha-MSH receptor (MC1).
- Alpha-MSH directly inhibits human neutrophil chemotaxis, likely via modulation of cAMP.
- These findings support the role of alpha-MSH as an anti-inflammatory agent by directly impacting neutrophil function.