Formyl-methionyl-leucyl-phenylalanine Induces Apoptosis in Murine Neurons: Evidence for NO-Dependent Caspase-9 Activation.

Chiara Porro,Maria Antonietta Panaro,Rosa Calvello,Dario Domenico Lofrumento,Teresa Trotta,Antonia Cianciulli

doi:10.3390/biology8010004

Chiara Porro, Maria Antonietta Panaro + Show 4 more

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https://doi.org/10.3390/biology8010004

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Abstract

Formyl-methionyl-leucyl-phenylalanine (fMLP) may be present in the brain in the course of some infectious diseases of the central nervous system (CNS), although little is known about its role. This investigation was performed to study the effect of fMLP on neuron apoptosis. Our results showed that fMLP treatment of primary cultures of neurons was able to induce morphological features of apoptosis in cell cultures, as well as activation of the intrinsic apoptotic pathway, through the upregulation of caspase-9 and caspase-3. This effect contextually occurred to the pro-apoptotic protein Bax activation and cytochrome c release. The in vitro fMLP treatment was also able to induce, in a dose-dependent manner, the increase of inducible nitric oxide synthase (iNOS) expression accompanied by an up-regulation of nitric oxide (NO) release. When neuron cultures were pre-treated with 1400 W, a selective iNOS inhibitor, all of the apoptotic features were significantly reversed. Overall, these results demonstrated that fMLP treatment of neurons leads to intrinsic apoptosis activation, through iNOS expression regulation, suggesting a role for fMLP in CNS neurodegenerative processes.

Highlights

N-formylated peptides such as N-formyl-L-methionyl-L-leucyl-phenylalanine act as potent chemoattractants
N-terminus may represent a “molecular pattern” identified by cells. These molecules are often linked with bacterial infections, and with danger signals deriving from damaged host cells/tissues, highlighting the importance for formyl peptide receptors (FPRs) in inflammatory responses [2,3]. fMLP is revealed to be present in some brain infectious diseases, as meningitis
Western blot analysis showed that the FPR2 antibody recognised a specific band as reported in Figure 1A, indicating specificity of the antibody; the 41 kDa band corresponds to the molecular weight of FPR2

Summary

Introduction

N-formylated peptides such as N-formyl-L-methionyl-L-leucyl-phenylalanine (fMLP) act as potent chemoattractants. These molecules derive from either degraded bacterial or mitochondrial proteins, and play a key role in defense mechanisms toward microbial infection or tissue injury by phagocyte engagement to the inflammation site [1]. N-terminus may represent a “molecular pattern” identified by cells. These molecules are often linked with bacterial infections, and with danger signals deriving from damaged host cells/tissues, highlighting the importance for formyl peptide receptors (FPRs) in inflammatory responses [2,3]. FMLP released from bacteria could gain access to the brain from the bloodstream through less tight blood–brain barrier (BBB) areas, represented, for example, by the circumventricular organs [4]. Since during inflammatory events BBB function may be compromised, neuronal dysfunction can worsen [5].

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