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Blood-sucking arthropods possess a variety of antihemostatic factors in their salivary glands to maintain blood fluidity during feeding. In this work we demonstrate the anti-hemostatic properties of lysophosphatidylcholine (lysoPC) isolated from the salivary glands of Rhodnius prolixus. First, we examined salivary glands of fourth and fifth instar nymphs for their phospholipid composition. The lumen displayed an accumulation of its phospholipid content, mainly phosphatidylcholine and lysoPC, with a 6-fold increase for the latter. To determine the presence of phospholipids in the saliva, fourth instar nymphs were fed with a 32 P-enriched blood meal. After 28 days their saliva was collected and subjected to lipid extraction, thin-layer chromatography, and autoradiography. The results showed the presence in the saliva of the same phospholipids present in the lumen. We then examined possible biological roles of these phospholipids when compared with other known effects of lysoPC. The luminal lipid extract and purified lysoPC from the lumen and saliva were tested for inhibition of washed rabbit platelets' aggregation induced by ␣-thrombin and platelet-activating factor. Both the luminal lipid extract and salivary lysoPC showed an increasing inhibition of aggregation, which correlated with the response of the platelets to standard lysoPC (up to 13 g/ml). Next, salivary lysoPC was incubated with porcine arterial endothelial cells for 24 h. After incubation, culture medium was assayed for nitric oxide and showed increased nitric oxide production, similar to control cells exposed to standard lysoPC (up to 20 g/ ml). Together these data demonstrate the presence of lysoPC in the saliva of Rhodnius prolixus and its potential anti-hemostatic activities.Hematophagous arthropods rely on a wide array of antihemostatic substances to counteract vertebrate responses to blood loss and to obtain their blood meal successfully (1). These salivary compounds show distinct properties and are generally involved with inhibition of coagulation, platelet aggregation, and vasoconstriction (2). These molecules include peptides such as tachykinins (3), maxadilan (4), nitric oxide (NO) 1 -binding proteins such as nitrophorins (5), and prostaglandins (6). The small lesions elicited by the mouthparts of the arthropod most likely evoke platelet aggregation and vasoconstriction by the vertebrate host. Therefore, the formation of the platelet plug is specifically inhibited by collagen inhibitors, apyrases, catechol oxidases, thrombin inhibitors, NO-releasing proteins, fibrinogen receptor agonists, and a specific platelet aggregation inhibitor (7,8). The complexity of anti-hemostatic mechanisms has recently been addressed with the use of proteomic techniques (9, 10). Hundreds of gene sequences were obtained, and most of them await future tests concerning the anti-hemostatic properties of the proteins they code for.Lysophosphatidylcholine (lysoPC) is a component of oxidized low-density lipoprotein, which is involved in the pathogenesis of atheroscleros...

Lipid transport in arthropods is achieved by highly specialized lipoproteins, which resemble those described in vertebrate blood. Here we describe purification and characterization of the lipid-apolipoprotein complex, lipophorin (Lp), from adults and larvae of the cowpea weevil Callosobruchus maculatus. We also describe the Lp-mediated lipid transfer to developing oocytes. Lps were isolated from homogenates of C. maculatus larvae and adults by potassio bromide gradient and characterized with respect to physicochemical properties and lipid content. The weevil Lp (465 kDa) and larval Lp (585 kDa), with hydrated densities of 1.22 and 1.14 g/mL, contained 34 and 56% lipids and 9 and 7% carbohydrates, respectively. In both Lps, mannose was the predominant monosaccharide detected by paper chromatography. SDS-PAGE revealed two apolipoproteins in each Lp with molecular masses of 225 kDa (apolipoprotein-I) and 79 kDa (apolipoprotein-II). The lipids were extracted and analyzed by thinlayer chromatography. The major phospholipids found were phosphatidylserine, phosphatidylcholine and phosphatidylethanolamine in adult Lp, and phosphatidylcholine, phosphatidylethanolamine and sphingomyelin in larval Lp. Hydrocarbons, fatty acids and triacylglycerol were the major neutral lipids found in both Lps. Lps labeled in the protein moiety with radioactive iodine ( 125 I-iodine) or in the lipid moiety with fluorescent lipids revealed direct evidence of endocytic uptake of Lps in live oocytes of C. maculatus.

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