Rhythmic autocrine activity in cultured insect epidermal cells

Abstract

It is now well established that ecdysteroids can be produced in insects in the absence of prothoracic glands. In this respect, it has been shown that cells in culture can produce ecdysteroids. Our aims were: (1) to determine whether ecdysteroid target cells of epidermal origin could also be the source of ecdysteroids; (2) to monitor more accurately the kinetics of ecdysteroid production; and (3) to check for possible relationships between this synthetic activity and dynamics of cell division. An insect cell line (IAL‐PID2) established from imaginal discs of the Indian meal moth, Plodia interpunctella, with wild‐type sensitivity to ecdysteroids was used in our study. Our results showed that the Plodia cell line exhibited autocrine activity. When division of IAL‐PID2 cells was synchronized, a rhythmic production of ecdysteroids was observed. However, further experiments indicated that this rhythmicity could be cell autonomous. This led us to anticipate the existence of two cell subpopulations that would be able to produce ecdysteroids rhythmically, a minor one that would be cell cycle serum‐independent population, and a major population that would need serum growth factors to proliferate and produce ecdysteroids. Qualitative study of the ecdysteroid content of the media clearly showed that ecdysone was the major immunoreactive product. Taken together, our findings clearly show that an insect cell line of epidermal origin is capable of rhythmic autocrine production of ecdysteroids. These results support the hypothesis that alternate sites for ecdysteroid production in vivo may exist and could play a role in local regulation of development. We now plan to determine the cellular basis of this rhythmic autocrine activity and to confirm the existence of growth factor‐autonomous cells in the culture as well as the potent role played by ecdysteroids in the cross‐talk between various cell subpopulations. Arch. Insect Biochem. Physiol. 44:7–16, 2000. © 2000 Wiley‐Liss, Inc.

Peripheral regulation by ecdysteroids of olfactory responsiveness in male Egyptian cotton leaf worms, Spodoptera littoralis

“…Samples were resuspended in buffer for an enzyme immunoassay (EIA) for ecdysteroid, adapted from Porcheron et al (1989), using polyclonal anti-20E antiserum AS4919 and a 2-Succinyl-20-hydroxyecdysone coupled to peroxidase (Gift from Jean-Paul Delbecque, Bordeaux, and Catherine Blais, Paris). The chromogenic reaction used o-Phenylenediamine (OPD, Sigma, France) and hydrogen peroxide solution (Mesnier et al, 2000), and Optical Density (OD) was measured at 450 nm. In our assay, ecdysone and 20E cross-reacted equally well with the AS4919 antiserum.…”

Endocrine Insights into the Evolution of Metamorphosis in Insects

“…In immature insects, the ecdysones are typically produced by the prothoracic glands or their anatomical equivalents (e.g., the ventral glands of Orthoptera) (104). In beetle larvae, however, oenocytes (118) and even general and disc epidermis (37,83) are also thought to synthesize and release ecdysones. Although the traditional product of the prothoracic gland is α-ecdysone, that of Manduca secretes a mixture of α-ecdysone (αE) and 3-dehydroecdysone (3DE), with the latter rapidly converted to α-ecdysone by blood enzymes (43).…”