Up‐regulation of ectonucleotidase activity after cortical stab injury in rats

Abstract

The objective of this study was to examine the changes in the activity and expression of ectonucleotidase enzymes in the model of unilateral cortical stab injury (CSI) in rat. The activities of ecto-nucleoside triphosphate diphosphohydrolase 1 (NTPDase 1) and ecto 5'-nucleotidase were assessed by measuring the levels of ATP, ADP and AMP hydrolysis in the crude membrane preparations obtained from injured left cortex, right cortex, left and right caudate nucleus, whole hippocampus and cerebellum. Significant increase in NTPDase and ecto 5'-nucleotidase activities was observed in the injured cortex following CSI, whereas in other brain areas only an increase in ecto 5'-nucleotidase activity was seen. Immunohistochemical analysis performed using antibodies specific to NTPDase 1 and ecto 5'-nucleotidase demonstrated that CSI induced significant changes in enzyme expression around the injury site. Immunoreactivity patterns obtained for NTPDase 1 and ecto 5'-nucleotidase were compared with those obtained for glial fibrillary acidic protein, as a marker of astrocytes and complement receptor type 3 (OX42), as a marker of microglia. Results suggest that up-regulation of ectonucleotidase after CSI is catalyzed by cells that activate in response to injury, i.e. cells immunopositive for NTPDase 1 were predominantly microglial cells, whereas cells immunopositive for ecto 5'-nucleotidase were predominantly astrocytes.

New insights regarding the regulation of chemotaxis by nucleotides, adenosine, and their receptors

“…Other studies implicate an inhibitory role of A 2B [64] and A 3 [65] receptors in microglial migration. Microglia (akin to neutrophils) express CD39 on their cell surface, thereby enabling the clearance of extracellular ATP and facilitating the generation of adenosine [66,67]. CD39-mediated hydrolysis of extracellular ATP is critical for this chemotaxis of microglia: Microglia isolated from CD39-knockout mice do not migrate in response to ATP or adenosine [68], but this response is restored in microglia treated with ATP and apyrase.…”

Perspectives of purinergic signaling in stem cell differentiation and tissue regeneration

“…Experimental evidence indicates liberation of adenosine into the extracellular medium after tissue damage together with down-regulation of AK expression, leading to adenosine accumulation and neuroprotection following injury [105]. ATP in the extracellular medium may attract astrocytes and microglia to the site of injury in order to assist tissue repair [106]. In the normal adult brain, ATP secreted by astrocytes stimulates NPC proliferation and migration, while P2Y receptor antagonists reversed this effect by inhibiting proliferation.…”

Activity of the astrocytes' adenosine signaling system components in model of traumatic brain injury in vivo and in vitro

“…Naši prethodni rezultati su pokazali da e-5NT ispoljava bifazne promene u aktivnosti i ekspresiji nakon ubodne povrede kore mozga u vidu ranog smanjenja [170], praćeno ushodnom regulacijom ekspresije i aktivnosti enzima do 2 nedelje nakon povrede [171,172]. Takođe smo pokazali da nakon povrede kore mozga dolazi do gubitka e-5NT na membrani neurona i povećanja ekspresije u e-5NT-pozitivnim reaktivnim astrocitima [171].…”

“…Ove promene su se ogledale u akutnom smanjenju ekspresije i aktivnosti, praćene ushodnom regulacijom e-5NT koja se održala 2 nedelje nakon TPM [171,172]. Rezultati naših i studija drugih grupa, ukazuju na to da u patološkim stanjima e-5NT može služiti kao generator Ado [81,245,279].…”

“…Ranije smo pokazali da hidroliza ATP i ADP ima dvofazan profil, sa padom u prva 24 časa koji prati značajan rast aktivnosti do petnaestog dana nakon povrede [172]. Ovde prikazani rezultati ukazuju da e-NTPD-aza2 možda takođe doprinosi primećenim promenama u hidrolizi nukleotida, bar kada je u pitanju ATP hidroliza.…”