Effect of ace inhibitors and TMOF on growth, development, and trypsin activity of larval Spodoptera littoralis

Abstract

Angiotensin converting enzyme (ACE) is a zinc metallopeptidase capable of cleaving dipeptide or dipeptideamide moieties at the C-terminal end of peptides. ACE is present in the hemolymph and reproductive tissues of insects. The presence of ACE in the hemolymph and its broad substrate specificity suggests an important role in processing of bioactive peptides. This study reports the effects of ACE inhibitors on larval growth in the cotton leafworm Spodoptera littoralis. Feeding ACE inhibitors ad lib decreased the growth rate, inhibited ACE activity in the larval hemolymph, and down-regulated trypsin activity in the larval gut. These results indicate that S. littoralis ACE may influence trypsin biosynthesis in the larval gut by interacting with a trypsin-modulating oostatic factor (TMOF). Injecting third instar larvae with a combination of Aea-TMOF and the ACE inhibitor captopril, down-regulated trypsin biosynthesis in the larval gut indicating that an Aea-TMOF gut receptor analogue could be present. Injecting captopril and enalapril into newly molted fifth instar larvae stopped larval feeding and decreased weight gain. Together, these results indicate that ACE inhibitors are efficacious in stunting larval growth and ACE plays an important role in larval growth and development.

A viral chitinase enhances oral activity of TMOF

“…In a recent study on Spodoptera littoralis larvae, the presence of Aea-TMOF receptors on the basolateral membrane of midgut cells has been hypothesized (Lemeire et al, 2008). The effect of ingested and injected Aea-TMOF on trypsin biosynthesis (Nauen et al, 2001) and on the growth of H. virescens larvae (Tortiglione et al, 2002;2003) also suggests the presence of a TMOF-like hormone in Lepidoptera, and, therefore, of receptors similar to those identified in mosquitoes.…”

Proteases as Insecticidal Agents

“…A separate review in this volume by Rodou and colleagues provides an in-depth overview of the insecticidal proteases of the bacterium Photorhabdus luminescens . Related to the use of proteolytic enzymes as insecticidal agents is exploitation of the insecticidal impact of the lack of proteases, such as plant expression of inhibitors of herbivore gut proteases [21], and the use of insect-derived, trypsin-modulating oostatic factor that inhibits trypsin biosynthesis in the insect gut [22,23]. The insecticidal effects of protease inhibition will not be considered in the current review.…”

The toxicity of angiotensin converting enzyme inhibitors to larvae of the disease vectors Aedes aegypti and Anopheles gambiae

“…Nevertheless, ACE inhibitors can be acutely toxic to insects, which contrasts with their life-span extending properties in rodents37 and the nematode, Caenorhabditis elegans 38. They have been useful in confirming important roles for ACE in reproduction, growth and development in several insect species30343539. In the mosquito Anopheles stephensi , females fed with ACE inhibitors in the blood meal or females mated with males supplied with ACE inhibitors in their sugar diet, lay significantly fewer eggs than normal323540.…”