Prostaglandins and related compounds, collectively know as eicosanoids, are crucial mediators of hemocytic immune responses to bacterial infections in larvae of the tobacco hornworm Manduca sexta, and likely in all insects. Virtually nothing is known about the biochemistry of eicosanoids in insect hemocytes. The overall goal of the proposed research is to investigate eicosanoid metabolism in hemocytes of M sexta as a first step toward gaining an understanding of the physiological roles of eicosanoids in insect immunology. The research in this proposal is designed to answer basic questions: 1-How do eicosanoid precursor fatty acids become free for eicosanoid biosynthesis? 2-Which eicosanoid species are biosynthesized by hemocytes? 3-Do pharmaceutical eicosanoid biosynthesis inhibitors have the same actions in mammals and in insect hemocytes? 1-In mammals, phospholipase A2 is thought to regulate eicosanoid biosynthesis by modulating the availability of free eicosanoid-precursor fatty acids. Radioactive substrates will be used to characterize the activity of this enzyme. 2-Hemocyte microsomes will be incubated with radioactive eicosanoid-precursor fatty acids, and eicosanoid biosynthesis will be monitored by radio-chromatography. 3-Eicosanoid biosynthesis inhibitors known from mammals will be characterized by adding selected inhibitors to preparations described in step 3. Actions in larvae will be monitored by injecting the inhibitors into larvae, then determining hemolymph eicosanoid titres by radioimmunoassay. The information gained in these studies in a model insect will provide compelling insights into the mechanisms of mediating cellular immune responses in hematophagous insects of medical importance. This work has implications for developing novel pest control strategies based on compromising cellular immunity.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI031509-03
Application #
2066476
Study Section
Tropical Medicine and Parasitology Study Section (TMP)
Project Start
1992-05-01
Project End
1995-04-30
Budget Start
1994-05-01
Budget End
1995-04-30
Support Year
3
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of Nebraska Lincoln
Department
Zoology
Type
Schools of Earth Sciences/Natur
DUNS #
555456995
City
Lincoln
State
NE
Country
United States
Zip Code
68588
Gadelhak, G G; Pedibhotla, V K; Stanley-Samuelson, D W (1995) Eicosanoid biosynthesis by hemocytes from the tobacco hornworm, Manduca sexta. Insect Biochem Mol Biol 25:743-9
Stanley-Samuelson, D W; Ogg, C L (1994) Prostaglandin biosynthesis by fat body from the tobacco hornworm, Manduca sexta. Insect Biochem Mol Biol 24:481-91
Gadelhak, G G; Stanley-Samuelson, D W (1994) Incorporation of polyunsaturated fatty acids into phospholipids of hemocytes from the tobacco hornworm, Manduca sexta. Insect Biochem Mol Biol 24:775-85
Miller, J S; Nguyen, T; Stanley-Samuelson, D W (1994) Eicosanoids mediate insect nodulation responses to bacterial infections. Proc Natl Acad Sci U S A 91:12418-22
Uscian, J M; Stanley-Samuelson, D W (1993) Phospholipase A2 activity in the fat body of the tobacco hornworm Manduca sexta. Arch Insect Biochem Physiol 24:187-201