The primary function of antimicrobial molecules is the interaction with
pathogens to clear infections. In this chapter, we discuss the role that antimicrobial
peptides (AMPs), nitric oxide (NO), and reactive oxygen species (ROS) play in the
elimination of intracellular bacteria and their induction by immunomodulators like
vitamin D, focusing on the mycobacterial infection. AMPs are the major mechanisms
to directly eliminate intracellular bacteria such as Mycobacterium tuberculosis or
Salmonella sp. Cathelicidins (LL-37) and β-defensins (HBD-2) are the most studied
AMPs, due to their relevance in the immunopathogenesis of several infectious diseases.
Additionally, the production of ROS also kills intracellular bacteria directly, especially
within the phagosome; patients with ROS deficiencies are susceptible to tuberculous
mycobacterial infections. However, excessive production of ROS might induce cell
death by apoptosis. The active form of vitamin D (1α,25(OH)2D3) is a key inducer of
antimicrobial mechanisms. Vitamin D is involved in redox homeostasis, regulating the
effect of ROS and NO to protect the cell integrity; and as an activator of anti-infective
pathways for pathogen elimination through induction of AMPs and autophagy. The
ability of induction of antimicrobial mechanisms confers these molecules a potential
use as adjunct therapies in several infections.
Keywords: Antimicrobial peptides (AMPs), Autophagy, β-defensins,
Cathelicidin, Hepcidin, IFN-γ, LL-37, M. tuberculosis, NADPH oxidase, Nitric
oxide (NO), Reactive oxygen species (ROS), Vitamin D, Vitamin D receptor
(VDR).
