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Do porins inhibit the macrophage phagocyting activity by stimulating the adenylate cyclase?
Abstract:
Porins interact with macrophage membranes and inhibit their phagocyting activity. We have tested the porin effect on a biologically relevant membrane-bound enzymic activity, the adenylate cyclase system, which appears to be stimulated both in the presence of Mn2+ and Mg2+ or Mg2+ + Gpp(NH)p. Moreover, for mice macrophages incubated in the presence of porins, there is an increase in the intracellular cAMP content after 5 min of incubation, with a maximum after 15 min of incubation. The results shown suggest that the porin effects on the adenylate cyclase can represent the molecular basis of the porin-dependent inhibition of the macrophages phagocytosis. Our point of view, which proposes a cAMP role in inhibiting the phagocyting activity in macrophages, is supported also by the results of the experiments carried out in the presence of both dibutyryl-cAMP or aminophylline. The phagocyting activity is inhibited in all cases and independently of the bacteria to be phagocyted.
Insights
Bacterial porins disrupt macrophage function by increasing intracellular cyclic adenosine monophosphate (cAMP). This molecular mechanism explains how porins inhibit macrophage phagocytosis, impacting immune responses.
Area of Science:
- Immunology
- Microbiology
- Molecular Biology
Background:
- Bacterial porins are known to interact with macrophage membranes, impairing their phagocytic capabilities.
- The precise molecular mechanisms underlying porin-induced inhibition of macrophage phagocytosis remain incompletely understood.
Purpose of the Study:
- To investigate the effect of porins on the adenylate cyclase system in macrophages.
- To determine the role of cyclic adenosine monophosphate (cAMP) in porin-mediated inhibition of macrophage phagocytosis.
Main Methods:
- Assessing adenylate cyclase activity in macrophage membranes in the presence of porins and divalent cations (Mn2+, Mg2+).
- Measuring intracellular cAMP levels in macrophages after incubation with porins.
- Evaluating the impact of exogenous cAMP (dibutyryl-cAMP) and aminophylline on macrophage phagocytic activity.
Main Results:
- Porins stimulate adenylate cyclase activity in macrophage membranes.
- Incubation with porins leads to a significant increase in intracellular cAMP levels in macrophages.
- Exogenous administration of dibutyryl-cAMP or aminophylline inhibits macrophage phagocytosis, irrespective of the bacteria involved.
Conclusions:
- Porin-induced stimulation of adenylate cyclase and subsequent elevation of intracellular cAMP levels represent a key molecular mechanism for inhibiting macrophage phagocytosis.
- Elevated cAMP levels play a crucial role in suppressing the phagocytic activity of macrophages, offering a potential target for therapeutic interventions.