Inducible nitric oxide synthase blockade with aminoguanidine, protects mice infected with Nocardia brasiliensis from actinomycetoma development

Arginase Signalling as a Key Player in Chronic Wound Pathophysiology and Healing

Arginase (ARG) represents an important evolutionarily conserved enzyme that is expressed by multiple cell types in the skin. Arg acts as the mediator of the last step of the urea cycle, thus providing protection against excessive ammonia under homeostatic conditions through the production of L-ornithine and urea. L-ornithine represents the intersection point between the ARG-dependent pathways and the urea cycle, therefore contributing to cell detoxification, proliferation and collagen production. The ARG pathways help balance pro- and anti-inflammatory responses in the context of wound healing. However, local and systemic dysfunctionalities of the ARG pathways have been shown to contribute to the hindrance of the healing process and the occurrence of chronic wounds. This review discusses the functions of ARG in macrophages and fibroblasts while detailing the deleterious implications of a malfunctioning ARG enzyme in chronic skin conditions such as leg ulcers. The review also highlights how ARG links with the microbiota and how this impacts on infected chronic wounds. Lastly, the review depicts chronic wound treatments targeting the ARG pathway, alongside future diagnosis and treatment perspectives.

Nitric oxide determines the development of actinomycetoma by Nocardia brasiliensis in eNOS knockout C57BL/6 mice

Mycetoma is a chronic human infectious disease that produces severe deformation frequently in the lower extremities. Etiological agents include fungi (eumycetoma) and bacteria (actinomycetoma) that produce similar clinical and microscopic changes. The clinical appearance includes swelling, abscesses, ulcers, scars and sinuses that drain purulent material with microbe microcolonies. The pathogenesis of actinomycetoma has been studied mainly in rodents. Using this approach, it was found that Nocardia brasiliensis produces proteases that may play a role in tissue damage, as well as immunosuppressive molecules, such as brasilicardin A. Nitric oxide (NO) is a molecule with biological activities depending on its local concentration. Its effect on killing intracellular bacteria such as Mycobacterium tuberculosis has been known for decades. NO plays an important role in innate and adaptive immunity. It can promote or suppress some biological activities despite its short half-ife. NO is produced by three different nitric oxide synthases (NOS). We used the genetic blockade of eNOS in C57BL/6 mice to demonstrate the role of NO in actinomycetoma development. Inflammation and actinomycetoma were prevented in genetically modified mice infected with N. brasiliensis. T cell proliferation was increased in these rodents, and antibody production, IL-6 and IL-10 expression were similar and TNF-α was lower.