3.4. P2C7 Is a Proinflammatory Stimulus to Macrophages
The effects of the P1A3 and P2C7 peptides on the expression of proinflammatory mediators in BMDMs are shown in Figure 4. LDL (−) induced a significant proinflammatory effect by increasing the mRNA expression of TNF-α, IL-1 α, COX-2, and NOS2. IL-10 is also induced by LDL (−) as previously reported (5). Only P2C7 stimulated the expression of TNF-α, IL-1 α, NOS2, and IL-10, which demonstrates that this peptide mimics the action of LDL (−) on macrophages although at less intensity (Figure 4A–F). In addition, macrophage activation by P2C7 does not depend on its internalization considering that Brefeldin A did not inhibit the expression of TNF-α and NOS2, as shown in Figure 4G–I. Moreover, both LDL (−) and P2C7 increased NO production compared to the control and the P1A3 peptide (Figure 4J). Furthermore, only P2C7 increased CCL2 and TNF-α secretion compared to P1A3 and control (Figure 4K).
To reinforce the evidence of the BMDM phenotype under P2C7 stimulation, the following markers were analyzed: M1 phenotype (MHC II, CD80, and CD 86), and M2 phenotype (CD206). P2C7-treated macrophages increased the M1 phenotype population (Figure 5) without affecting the M2 population (Figure S8).