Mediation of inducible nitric oxide and immune-reactive lysozymes biosynthesis by eicosanoid and biogenic amines in flesh flies

Abstract

Nitric oxide (NO) plays various roles in insect immunity: as a cytotoxic component and as a signalling molecule; and immune-reactive lysozymes (IrLys) provide a first line of humoral immune functions against invading bacteria. Although there is considerable literature on eicosanoid and biogenic monoamine actions on insect immunity, there is no information on the role(s) of these chemicals in inducing NO and IrLys. We addressed this gap by challenging third instarSarcophaga(Liopygia)argyrostoma(Robineau-Desvoidy) with the Gram-positive bacteriumMicrococcus luteus. Here, we report that bacterial challenge induces elevation of NO and IrLys concentrations in haemocytes and in the fat body. The plasma pool content is comparatively low. Eicosanoid biosynthesis inhibitors (EBIs) lead to suppression of both NO and IrLys levels. Control larvae have low constitutive levels of NO and lysozyme concentrations. Octopamine (OA) elicits elevation of NO and IrLys concentrations. A similar effect is obtained by 5-hydroxytryptamine (5-HT) for NO. These data indicate immune-mediating roles of eicosanoids, OA and 5-HT in NO and IrLys activities.

Pathogen‐mediated modulation of host metabolism and trophic interactions in Spodoptera littoralis larvae

“…As a lysosomal enzyme, AcP may have a role in autophagy and cell turnover as well as defense (Xia et al, 2000). Thus, the significant increase in AcP activity observed in the current study may have been an attempt by the infected insect to defend against the invading pathogens, where lysozymes are a component of humoral immunity (Mohamed et al, 2016, 2018; Satyavathi et al, 2018; Dorrah et al, 2019). Similarly, increased AcP activity due to infection with entomopathogens has been reported by several authors (Xia et al, 2001; Mirhaghparast et al, 2013; Vidhya et al, 2016).…”

Regulators and signalling in insect antimicrobial innate immunity: Functional molecules and cellular pathways

“…Cellular reactions refer to hemocyte-mediated immune functions, e.g., phagocytosis, nodulation, and encapsulation [12,13]. Humoral reactions include production of antimicrobial peptides (AMPs) [14], complex enzymecascades that regulate activation of precursors of immune-related molecules such as prophenoloxidase (PPO) [15], pro-Spaetzle (proSpz) [16], and proplasmatocyte-spreading peptide (proPSP) [17], production of humoral pattern recognition receptors (PRRs) and lytic enzymes [18,19], and reactive intermediates of oxygen (ROI) and nitrogen (RNI) [20]. This classification of immune responses into cellular and humoral is arbitrary since many humoral factors affect cellular functions and several humoral molecules are produced by hemocytes.…”

Metamorphosis-related changes in the free fatty acid profiles of Sarcophaga (Liopygia) argyrostoma (Robineau-Desvoidy, 1830)

“…Various metabolites of C20:4 (arachidonic acid), known as eicosanoids, stimulate oviposition in crickets, regulate the function of Malpighian tubules in mosquitoes or ants, and control thermoregulation in cicadas 71 . They also play crucial roles in the mediation of insect cellular and humoral immunity 72,73 ; for example, in S. argyrostoma, they were found to mediate and coordinate the biosynthesis of NO and lysozyme in response to bacterial challenge 27 , and to participate in the LPS-dependent activation of the IMD pathway in Sarcophaga peregrina 74 . In a study of the internal extract of S. carnaria, Gołębiowski and co-workers found C20:5 to be present at 90-times higher concentrations in females than males; they propose that the compounds may play an important role in vitellogenesis 26 .…”

“…Several species are synanthropic and may be responsible for the mechanical transmission of pathogens to food and humans, with potential consequences for public health 12 , 17 , 18 . They are suitable animals for studying the physiology and biochemistry of insects, particularly their endocrinology 19 , 20 , diapause 21 – 23 , reproduction 24 and immunity 25 – 27 . In addition, they are regarded as having high forensic value, due to their ovoviviparity (or ovolarviparity): they deposit maggots instead of eggs directly on a corpse, and due to the larger size of the larvae and their higher efficiency of sarcophagid flies, they act as convenient markers of decay 28 – 31 .…”