Expression of PACAP-Like Compounds During the Caudal Regeneration of the Earthworm Eisenia fetida

Abstract

The regeneration of the ventral nerve cord ganglion and peripheral tissues was investigated by radioimmunoassay and immunohistochemistry in the model animal, Eisenia fetida (Annelida, Oligochaeta). It is now well-established that pituitary adenylate cyclase-activating polypeptide (PACAP) is a neurotrophic factor, playing important roles in the development of the nervous system in vertebrate animals. Based on the apparent evolutionary conservation of PACAP and on the several common mechanisms of vertebrate and invertebrate nervous regeneration, the question was raised whether PACAP has any role in the regeneration of the earthworm nervous system. As a first step, we studied the distribution, concentration, and time-course of PACAP-like immunoreactivity during caudal regeneration of both lost segments and the ventral nerve cord ganglia in E. fetida. A strong upregulation of PACAP-like immunoreactivity was observed in most tissues following injury as determined by radioimmunoassay and immunohistochemistry. Significant increases in the concentration of PACAP-like compounds were found in the body wall, alimentary canal, and in coelomocytes. The most characteristic morphological feature was the accumulation of immunolabeled neoblasts in the injured tissues, especially in the ventral nerve cord ganglion that initiates and mediates regeneration processes. Our present results show that PACAP/PACAP-like peptides accumulate in the regenerating tissues of the earthworm, suggesting trophic functions of these compounds in earthworm tissues similarly to vertebrate species.

Immune system participates in brain regeneration and restoration of reproduction in the earthworm Dendrobaena veneta

“…The involvement of fluid-suspended coelomocytes in the regeneration of earthworm tissues was recorded by Liebmann as early as 1943 and 1945, who found that by experimentally depleting the coelomocytes, excised segment restoration was partially inhibited or totally blocked Liebmann (1943Liebmann ( , 1945. Participation of coelomocytes in wound plug formation and re-modeling by phagocytic activities, as well as in the delivery of essential nutrients and growth-stimulating molecules to the locus of regeneration, was described by Jamieson (1981) and Varhalmi et al (2008). In an earlier publication, Moment (1974) implicated a stimulatory regeneration role for the so-called 'yellow pigment' derived from a certain coelomocyte cohort.…”

Pituitary Adenylate Cyclase‐activating Polypeptide‐like Compounds Could Modulate the Activity of Coelomocytes in the Earthworm

“…After anesthesia 20 caudal segments of 10 earthworms were cut with a scalpel. Coelomocytes were collected from intact and 5‐day‐old regenerating specimens and used either for light and electron microscopy after immunostaining 4,5 or for radioimmunoassay (RIA) as described previously 4 . For Western blot analysis, coelomocytes and controls (mouse and adult earthworm neural tissues) were lysed in Radio Immuno Precipitation Assay (RIPA) buffer supplemented with a protease inhibitor cocktail (Sigma‐Aldrich, St. Louis, MO) on ice for 15 min.…”

“…We have recently shown the accumulation of coelomocytes expressing pituitary adenylate cyclase‐activating polypeptide (PACAP)‐like compounds in severed and renewed body segments of the regenerating earthworm Eisenia fetida. 4 Because there are no data available on the biological effects of PACAP(‐like) compounds on the coelomocyte system of earthworms, we studied both the presence of PACAP‐like compounds and the expression and ultrastructural distribution of the PACAP‐specific PAC1 receptor (PAC1R) in earthworm coelomocytes.…”

Occurrence, Distribution, and Physiological Function of Pituitary Adenylyl Cyclase-Activating Polypeptide in Invertebrate Species

“…Using PACAP-27 (n° 88121-5 antibody; (39,40)) or PACAP-38 antibodies (anti-PACAP-38, Peninsula, CA, USA, (14,39)) immunopositive cells and fibers were observed in cerebral, medial and lateral parts of the subesophageal and ventral cord ganglia. In the peripheral nervous system, PACAP-IR was found in the enteric nervous system, epidermal sensory cells and clitellum (reproductive organ).…”