Nitric oxide stimulates melanin production during immune response in Apis mellifera.

NEGRI PEDRO; MAGGI MATIAS; MASSAZZA DIEGO; CORREA ARAGUNDE NATALIA; EGUARAS MARTIN; LAMATTINA LORENZO

Mendoza

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biologia Molecular; 2012

Sociedad Argentina de Investigación en Bioquímica y Biologia Molecular

The honey bee Apis mellifera is known to be affected by many parasites. The A. mellifera immune system is a central weapon against parasites. Insects have a well developed innate immunity and a characteristic humoral immune response is melanisation. Melanin is derived mostly through the action of the enzyme phenoloxidase (PO) triggered by activated host blood cells or hemocytes. Little is known on the molecular mechanisms that activate hemocytes and initiate melanogenesis in honey bees. Hemocytes adhere to nonself particles attaching them by secreting cytotoxic compounds like reactive oxygen species (ROS) and reactive nitrogen intermediates (RNIs). Nitric oxide (NO) is a multifunctional RNI generated by the enzyme NO synthase (NOS) in insects functioning as a cell signalling molecule in immune responses. We have previously reported that NO plays a role in the immune activation of A. mellifera hemocytes. In the present study we analyzed the role of NO in melanogenesis. The formation of melanin was studied in the presence of the NO donor sodium nitroprusside (SNP) or the NO scavenger carboxi-PTIO (CPTIO) using A. mellifera haemolymph. While SNP enhanced melanisation, CPTIO reduced the formation of the pigment suggesting that NO acts as a promoter of melanogenesis in A. meliffera. Experiments are in progress to link the NOS substrate L-Arginine with NO production and melanisation.