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For malaria transmission, Plasmodium parasites must develop in the mosquito vector. Oxidative stress in the insect midgut, triggered by environmental changes (e.g., pH and temperature), influences the cellular signaling involved in differentiation from gametocytes to mobile ookinetes for the purpose of parasite survival. Oxidative stress activates the homeostatic response to stress characterized by the phosphorylation eIF2α, the attenuation of protein synthesis, and the transcription of genes participating in the unfolded protein response and antioxidant processes, forming a part of an integrated stress response (ISR). We hypothesized that ISR operates during the differentiation of gametocytes to ookinetes to assure Plasmodium survival. Using in-vitro conditions resembling the mosquito midgut conditions, we cultured Plasmodium berghei gametocytes to ookinetes and evaluated the redox balance by detecting reactive oxygen species and superoxide dismutase activity. Additionally, we evaluated the phosphorylation of eIF2α, the attenuation of the global protein synthesis, and the gene expression of cellular stress markers (e.g., endoplasmic reticulum chaperones and antioxidant molecules, measured by reverse-transcription quantitative polymerase chain reaction), finding that these processes were all taking place, probably to improve survival during the differentiation of Plasmodium berghei ookinetes.

BackgroundThe behaviour of Anopheles spp. mosquitoes, vectors for Plasmodium parasites, plays a crucial role in the propagation of malaria to humans. Consequently, it is important to understand how the behaviour of these mosquitoes is influenced by the interaction between the brain and immunological status. The nervous system is intimately linked to the immune and endocrine systems. There is evidence that the malaria parasite alters the function of these systems upon infecting the mosquito. Although there is a complex molecular interplay between the Plasmodium parasite and Anopheles mosquito, little is known about the neuronal alteration triggered by the parasite invasion. The aim of this study was to analyse the modification of the proteomic profile in the An. albimanus brain during the early phase of the Plasmodium berghei invasion.ResultsAt 24 hours of the P. berghei invasion, the mosquito brain showed an increase in the concentration of proteins involved in the cellular metabolic pathway, such as ATP synthase complex alpha and beta, malate dehydrogenase, alanine transaminase, enolase and vacuolar ATP synthase. There was also a rise in the levels of proteins with neuronal function, such as calreticulin, mitofilin and creatine kinase. Concomitantly, the parasite invasion repressed the expression of synapse-associated proteins, including enolyl CoA hydratase, HSP70 and ribosomal S60 proteins.ConclusionsIdentification of upregulated and downregulated protein expression in the mosquito brain 24 hours after Plasmodium invaded the insect midgut paves the way to better understanding the regulation of the neuro-endocrine-immune system in an insect model during parasite infection.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1830-9) contains supplementary material, which is available to authorized users.

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Background Insect neuropeptides, mainly synthesized in the brain, play a central role in the control of many physiological processes. A neuropeptidome of the mosquito Nyssorhynchus albimanus was described based in a comparative analysis of the mosquito genome complemented with high-throughput sequencing of brain transcriptomes. In addition, neuropeptides differentially expressed during Plasmodium infection were identified.Results We identified 3,811 transcripts associated to translation, oxidation-reduction process, protein binding, ATP binding, integral components of membrane and ribosome, among others. We identified 29 neuropeptide transcripts that predicted at least 60 biopeptides, including pyrokinin, glycoprotein hormone alpha (GPA2), prothoracicotropic hormone, neuropeptide-like precursor 1 (NPLP1), allatostatin C, orcokinin, corazonin, adipokinetic hormone I, SIFamide, pyrokinin capa-like, pigment-dispersing factor, adipokinetic hormone/corazonin-related peptide (ACP), tachykinin-related peptide, trissin, neuropeptide F, short neuropeptide F (sNPF), diuretic hormone 31, bursicon, crustacean cardioactive peptide (CCAP), allatotropin, allatostatin 1, partner of bursicon (PBURS), ecdysis triggering hormone (ETH), diuretic hormone 44 (Dh44), insulin-like peptides 5, 1, 3, 7, 2 (ILPs) and eclosion hormone (EH) and seven neuropeptide receptors. Transcript mapping to the Ny. albimanus genome provided evidence for the re-annotation of the myosuppressin gene. A quantitative analysis documented increased expression of adipokinetic hormone/corazonin-related peptide, pyrokinin and corazonin in the mosquito brain after Plasmodium berghei infection.Conclusion This work represents an initial effort to characterize the neuropeptide repertoire of Ny. albimanus and provides new information for understanding neuroregulation of the mosquito response during Plasmodium infection .