Mortality effects of eicosanoid biosynthesis inhibitors on Spodoptera littoralis larvae co-injected with the bacteria, Serratia marcescens

Abstract

The first step of the cellular defense reactions to bacterial, fungal and some viral infections in insects is nodulation. We posed the hypothesis that Spodoptera littoralis, expresses melanoic nodulation reactions to bacterial challenge and that injecting S. littoralis larvae with eicosanoid biosnthesis inhibitors (EBIs) plus bacteria would increase larval mortality. Injecting larvae with EBIs, immediately before intrahemocoelic injections of the bacterium, Serratia marcescens, sharply reduced the nodulation response to bacterial challenges. Separate treatments with specific inhibitors including dexamethasone (a phospholipase A₂ inhibitor), indomethacin, naproxen, ibuprofen, (cyclooxygenase inhibitors), esculetin (a lipoxygenase inhibitor) and Phenidone (dual cyclooxgenase/lipoxygenase inhibitor) impaired the ability of S. littoralis to form nodules in reaction to bacterial challenge. All concentrations of S. marcescens alone, applied to S. littoralis, caused low mortality of the larvae. However, an increased mortality of the larvae was seen when S. marcescens was co-injected with the EBIs with different modes of action. These findings support our hypothesis that virulent effects of entomopathogenic bacteria can be increased when S. littoralis immune systems were suppressed.  

Keywords

• Insect cellular immunity, nodulation, eicosanoid, bacteria, Spodoptera littoralis

Eikosanoid biyosentezi inhibitörleri Serratia marcescens bakterisi ile birlikte Spodoptera littoralis larvalarına uygulandığında larvalar üzerindeki ölüm etksi

Öz

Böceklerde bakeri, fungus ve bazı virüs hastalıklarına karşı oluşan hücresel bağışıklıklardan ilki nodülasyon reaksiyonudur. Bu çalışmada Spodoptera littoralis larvalarında Serratia marcescens bakterisine karşı oluşan nodülasyon reaksiyonu, bakterinin larvalar üzerindeki ölüm etkisi ve bakteri ile birlikte eiokosanoid biyosentezi inhibitörleri larvalara uygulandığında larvaların ölüm oranını etkileyip etkilemeyeceği test edilmiştir. S. littoralis larvalarına bakteri uygulamasında hemen önce eiokosanoid biyosentezi inhibitörleri enjekte edildiğinde böceklerede bakteriye karşı oluşan nodül sayısında önemli derecede azalma olmuştur. Tüm S. Marcescens bakteri konsantrasyonları larvalara tek başına uygulandığında düşük oranda larva ölümü ortaya çıkmıştır. Diğer taraftan S. marcescens bakterisi ile birlikte eikosanoid biyosentezi inhibitörleri S. littoralis larvalarına uygulandığında larvalar üzerindeki ölüm oranı yalnız bakteri uygulanan larvalara oranla önemli derecede yükselmiştir. Bu bulgular böceklerin bağışıklık sistemi baskı altına alındığında,  S. marcescens bakterisinin entomopatojen etkisinin arttığını göstermiştir. 

Anahtar Kelimeler

• Böcek hücresel bağışıklığı, nodülasyon, eikosanoid, bakteri, Spodoptera littoralis

Kaynakça

1. Connick, W.J., W.L.A. Osbring, M.S. Wright, K.S. Williams, D.J. Daigle, D.L. Boykin & A.R. Lax, 2001. Increased mortality of Coptotermes formosanus (Isoptera: Rhinotermitidae) exposed to eicosanoid biosynthesis inhibitors and Serratia marcescens (Eubacteriales: Enterobactericeae). Environmental Entomology. 30:449-455.
2. Dean, P., J.C. Gadsden, E.H. Richards, J.P. Edwards, A.K. Charnley & S.E. Reynolds, 2002. Modulation by eicosanoid biosynthesis inhibitors of immune responses by the insect Manduca sexta to the pathogenic fungus Metarhizium anisopliae. Journal of Invertebrate Pathology. 79: 93-101.
3. Gillespie, J.A., M.R. Kanaost & T. Trenzcek, 1997. Biological mediators of insect imunity. Annual Review of Entomology, 47: 611-643.
4. Howard, R.W., J.S. Miller & D.W. Stanley, 1998. The influence of bacterial species and intensity of infections on nodule formations in insect. Journal of Insect Physiology. 44: 157-164.
5. Leulier, F., C. Parquet, S. Pili-Floury, J.H. Ryu, M. Caroff, W.J. Lee, D. Mengin-Lecreulx & B. Lemaitre, 2003. The Drosophila immune system detects bacteria through specific peptidoglycan recognition. Nature Immunology 4: 478–484.
6. Lord, J.J., S. Anderson & D.W. Stanley, 2002. Eicosanoids mediate Manduca sexta cellular response to the fungal pathogen Reproductive Physiology and Biochemistry. 51: 46–54. bassiana: A role for the lipoxygenase pathway. A.R.C. Unit of
7. Mandato, C.A,. W.L. Diehl-Jones, S.J. Moore & R.G.H. Downer, 1997. The effects of eicosanoid biosynthesis inhibitors on prophenoloxidase activation, phagocytosis and cell spreading in Galleria mellonella. Journal of Insect Physiology. 43: 1-8.
8. Miller, J.S., T. Nguyen & D.W. Stanley-Samuelson, 1994. Eicosanoids mediate insect nodulation responses to bacterial infections. Proceedings of the National Academy of Sciences of the United States of America. 91: 12418-12422.

9. Miller, J.S. & D.W. Stanley, 1998. “The Nodule Formation Reaction to Bacterial Infection: Assessing the Role of Eicosanoids, 265-270”. In: Techniques in Insect Immunity (Eds: A. Wiesner, A. G. Dumphy & V. J. Marmaras). SOS publications, Fair Haven, Cornell University NJ. 304 pp.
10. Morishima, I., Y. Yamano, K. Inoue & N. Matsuo, 1997. Eicosanoids mediate induction of immune genes in the fat body of the silkworm, Bombyx mori. FEBS Letters, 419: 83-86.
11. SAS Institute Inc. 1989. SAS/STATR User's Guide, Version 6, 4th Ed., vol 2. SAS Institute Inc., Cary, NC.
12. Satyavathi, V.V., A Minz & J. Nagaraju, 2014. Nodulation: An unexplored cellular defense mechanism in insects. Cell. Sign. 26: 1753-1763.
13. Stanley-Samuelson, D.W., E. Jensen, K.W. Nickerson, K. Tiebel, C.L. Ogg & R.W. Howard, 1991. Insect immune response to bacterial infection is mediated by eicosanoids. Proceedings of the National Academy of Sciences of the United States of America. 88: 1064-1068.
14. Stanley, D.W. 2000. Eicosanoids in Invertebrate Signal Transduction Systems. Princeton University Press, Princeton, NJ.
15. Stanley, D.W. 2006. Prostaglandins and other eicosanoids in insects: Biological significance. Annual Review of Entomology. 51:25-44.
16. Stanley, D.W. & J.S. Miller, 2006. Eicosanoid actions in insect cellular immune functions. Entomologia Experimentalis et Applicata. 119: 1-13.
17. Stanley, D.W. & Y. Kim, 2014. Eicosanoid signaling in insects: from discovery to plant protection. Critical Reviews in Plant Sciences, 33: 20-63.
18. Strand, M.R. 2008. “Insect Hemocytes and Their Role in Immunity, 25-47”. In: Insect Immunology (Ed: N.E. Beckage),Academic Press, Elsevier, Amsterdam. 360 pp.
19. Tunaz, H. 2006. Eicosanoid biosynthesis inhibitors influence mortality of Pieris brassicae larvae co-injected with fungal conidia. A.R.C. Unit of Reproductive Physiology and Biochemistry. 63: 93-100.
20. Tunaz, H. & M. Küsek, 2012. “The role of eicosanoid biosynthesis inhibitors on mortality of Blattella germanica adults co-injected with the bacteria; Serratia marcescens, 29-32”. Second International Symposium of Biopesticides and Ecotoxicological Network (September 24-26, 2012 Bangkok), Thailand.