Hypoxia-induced differential apoptosis in the central nervous system of the sturgeon (Acipenser shrenckii)

Abstract

Hypoxia is a frequent challenge to aquatic vertebrates as compared with that for their terrestrial counterparts. All vertebrates respond to hypoxia in a similar, but not identical manner, indicating that these responses appeared early in the evolution of vertebrates. The aim of this study is to find out the effects of hypoxia on apoptosis in the central nervous system (CNS) of sturgeon, an archaic fish. With the regional specialization of the CNS, we hypothesize that if cell death does occur, the response will vary between regions, i.e., some CNS areas will be more susceptible to hypoxia than the others would. Sturgeons (Acipenser shrenckii) were subjected to hypoxia by exposure to either air or hypoxic water. After 6- or 30-h recovery they were sacrificed and the following regions of the CNS: retina, olfactory lobe, optic tectum, pituitary, cerebellum, pons/medulla, and spinal cord were examined by the terminal transferase mediated dUTP nick end labeling technique and for the cleaved fragment of activated caspase-3 by Western blotting. In hypoxia-treated sturgeons, the retina, optic tectum, pituitary, and spinal cord were found to have significantly more apoptotic cells than did untreated sturgeons at both 6 and 30 h after the hypoxic insults, indicating prolonged damage. Apoptosis was confirmed by Western blotting of the cleaved fragment of activated caspase-3. Olfactory lobe, cerebellum, and pons/medulla had relatively few apoptotic cells. The CNS of sturgeon showed a differential pattern of apoptosis in response to hypoxia.

Effects of complete replacement of fish oil with plant oil on gastrointestinal cell death, proliferation and transcription of eight genes’ encoding proteins responding to cellular stress in Atlantic salmon Salmo salar L.

“…During apoptosis, caspase-activated endonucleases cause doublestranded DNA breaks. Staining of double or single DNA strand breaks by terminal transferase mediated dUTP nick end labelling technique (TUNEL) has been used as an indicator for apoptotic conditions under several environmental conditions in fishes (Piechotta et al, 1999;Imajoh et al, 2005;Lu et al, 2005). Changes in normal intestinal cell renewal has been suggested as early indicators for abnormal or toxic conditions to the GI tract (Uni et al, 1998;Berntssen et al, 2003Berntssen et al, , 2004Sheen-Chen et al, 2003;Hemre et al, 2004).…”

Fish as model systems for the study of vertebrate apoptosis

“…In addition, caspase-3 was differentially expressed during zebrafish development [47]. Subsequent studies confirmed a role for caspase-3 in mediating stress-induced cell death in Atlantic salmon exposed to hyperthermia [44], in sea bass (Dicentrarchus labrax L.) in response to bacterial infection [48], in zebrafish exposed to DNA damaging conditions [18,49,50], and in sturgeon (Acipenser schrenckii) during prolonged hypoxia [51]. The importance of caspase-3 in embryonic development was corroborated by showing tissue-and stage-specific expression in Atlantic salmon [44].…”

Perinatal hypoxia induces subsequent retinal degeneration in the offspring of ovoviviparous fish, Xiphophorous maculates

“…VEGF (vascular endothelial growth factor) immunocytochemistry was performed for tagging neovascularization, and lactic acid dehydrogenase (LDH) immunocytochemistry was used for detecting necrosis. All experiments were performed on paraffin sections of various specimens as described previously 6,13,14 . The TUNEL kit was purchased from Chemicon (Temecula, CA, USA), the VEGF and LDH antibody from Santa Cruz Biotech (California, CA, USA), and the ABC (avidin‐biotin complex testing) immunocytochemistry kit from Zymed (San Francisco, CA, USA).…”

“…In humans, it has been reported that intrapartal asphyxia could result in a high percentage (over 30%) of patients developing subsequent malformations of the CNS 1 . Aquatic hypoxia in fish poses an even greater challenge than hypoxia in land vertebrates, and the presence of apoptotic cells has been pronounced in the nervous systems of sturgeons rendered hypoxic 5,6 . In other species of fish, such as the crucian carp, and some freshwater turtles and frogs, the effects of hypoxia have been less obvious 7,8 .…”