The Crustacean Central Nervous System in Focus: Subacute Neurodegeneration Induces a Specific Innate Immune Response

Abstract

To date nothing is known about the subacute phase of neurodegeneration following injury in invertebrates. Among few clues available are the results published by our group reporting hemocytes and activated glial cells at chronic and acute phases of the lesion. In vertebrates, glial activation and recruitment of immunological cells are crucial events during neurodegeneration. Here, we aimed to study the subacute stage of neurodegeneration in the crab Ucides cordatus, investigating the cellular/molecular strategy employed 48 hours following ablation of the protocerebral tract (PCT). We also explored the expression of nitric oxide (NO) and histamine in the PCT during this phase of neurodegeneration. Three immune cellular features which seem to characterize the subacute phase of neurodegeneration were revealed by: 1) the recruitment of granulocytes and secondarily of hyalinocytes to the lesion site (inducible NO synthase- and histamine-positive cells); 2) the attraction of a larger number of cells than observed in the acute phase; 3) the presence of activated glial cells as shown by the round shaped nuclei and increased expression of glial fibrillary acidic protein. We suggest that molecules released from granulocytes in the acute phase attract the hyalinocytes thus moving the degeneration process to the subacute phase. The importance of our study resides in the characterization of cellular and biochemical strategies peculiar to the subacute stage of the neurodegeneration in invertebrates. Such events are worth studying in crustaceans because in invertebrates this issue may be addressed with less interference from complex strategies resulting from the acquired immune system.

Injury-Induced Innate Immune Response During Segment Regeneration of the Earthworm, Eisenia andrei

“…Our findings are further supported by the active involvement of immune cells in the regeneration of the central nervous system (CNS), demonstrated in a crustacean ( Ucides cordatus ) [ 29 ]. Furthermore, several antimicrobial peptides (AMPs) (e.g., theromacin, neuromacin, Hm -lumbricin) have been shown to enhance the repair of damaged axons in the CNS of the leech Hirudo medicinalis [ 30 ].…”

3‐acetylpyridine‐induced degeneration in the adult ascidian neural complex: Reactive and regenerative changes in glia and blood cells

“…Therefore, although it has always been claimed that gliosis occurring after injury in the vertebrate CNS may influence the degree of success of the spontaneous regeneration process in this tissue, here, using another animal model, ascidians, we can suggest that the glia was reduced and another cell type was added (CD34 expressing cells). This may be similar to what occurred with the crustacean U. cordatus : hemocytes were recruited to a lesion produced in the protocerebral tract, suggesting that molecules released in the acute phase attracted hyalinocytes (young blood cells), initiating the subacute phase of regeneration (Chaves da Silva et al, , ). However, we must keep in mind that irrespective of any lesion, crustaceans show adult neurogenesis, and the neurogenic niche and vascular system are closely related (Sullivan et al, ; Chaves da Silva et al, ).…”

Functional Adaptations of Hemocytes of Aplysia depilans (Gmelin, 1791) and Their Putative Role in Neuronal Regeneration

“…Moreover, circulating blood cells appeared to be able to infiltrate the injured CNS where, together with microglia, they stimulated reparation [17]. Da Silva suggests that molecules released in the acute phase of injury attract hemocytes, differentiating these cells into other defense cells or lineages [18,19].…”