Cyanobacterium producing cylindrospermopsin cause histopathological changes at environmentally relevant concentrations in subchronically exposed tilapia (Oreochromis niloticus)

Abstract

The acute toxicity of cylindrospermopsin (CYN) has been established in rodents, based on diverse intraperitoneal an oral exposure studies and more recently in fish. But no data have been reported in fish after subchronic exposure to cyanobacterial cells containing this cyanotoxin, so far. In this work, tilapia (Oreochromis niloticus) were exposed by immersion to lyophilized Aphanizomenon ovalisporum cells added to the aquaria using two concentration levels of CYN (10 or 100 μg CYN L(-1)) and deoxy-cylindrospermopsin (deoxy-CYN) (0.46 or 4.6 μg deoxy-CYN L(-1)), during two different exposure times: 7 or 14 d. This is the first study showing damage in the liver, kidney, hearth, intestines, and gills of tilapia after subchronic exposure to cyanobacterial cells at environmental relevant concentrations. The major histological changes observed were degenerative processes and steatosis in the liver, membranous glomerulopathy in the kidney, myofibrolysis and edema in the heart, necrotic enteritis in the gastrointestinal tract, and hyperemic processes in gill lamellae and microhemorrhages. Moreover, these histopathological findings confirm that the extent of damage is related to the CYN concentration and length of exposure. Results from the morphometric study indicated that the average of nuclear diameter of hepatocytes and cross-sections of proximal and distal convoluted tubules are useful to evaluate the damage induced by CYN in the main targets of toxicity.

Immunohistochemical Approach to Study Cylindrospermopsin Distribution in Tilapia (Oreochromis niloticus) under Different Exposure Conditions

“…The highest liver CYN-immunopositivity correlates with the histopathological lesions described by light and electron microscopy in tilapia ( O. niloticus ) acutely and sub-chronically exposed to the same conditions as described in this work [30,39]. These histopathological alterations were also consistent with the exposure route and the time of euthanization.…”

Toxic cyanobacteria and cyanotoxins in European waters – recent progress achieved through the CYANOCOST Action and challenges for further research

“…The latter observation however is disputable N o n -c o m m e r c i a l u s e o n l y as no studies on isolated cultures of this cyanobacterium were performed. Complementary studies have been recently conducted on the toxicity of CYN (Guzmán-Guillén et al, 2015;Sierosławska et al, 2015;), mechanisms of toxicity , biodegradation (Dziga et al, 2016) and biological role and allelopathy (B-Béres et al, 2015). These works have contributed valuable knowledge on these aspects but at the same time have revealed many gaps in understanding of the role(s) of CYN in aquatic ecosystems and its impact on their functioning (Sukenik et al, 2015).…”

Vitamin E pretreatment prevents histopathological effects in tilapia (Oreochromis niloticus) acutely exposed to cylindrospermopsin

“…However, for the kidney, contradictory results have been described, showing decreased cross‐sections of proximal and distal convoluted tubules (DCT) in fish exposed to pure CYN by oral and i.p. injection, specially after 5 days of exposure (Gutiérrez‐Praena et al, ), whereas Guzmán‐Guillén et al () found increases in this parameter after 7 days of exposure and decreases after 14 days.…”

“…Among the morphological changes, disorganized parenchymal architecture in the liver and light degenerative processes, dilated Bowman's space, glomerular capillary atrophy and hyperemia in the kidney, fibrolysis with marked edema in the heart, necrotic enteritis in the intestines, and tumefaction and hemorrhages in the gills, were reported for fish acutely exposed to pure CYN orally (Puerto et al, ), by intraperitoneal (i.p.) injection (Gutiérrez‐Praena et al, ), or subchronically exposed to cyanobacterial cells containing CYN by immersion (Guzmán‐Guillén et al, ).…”

“…Furthermore, morphometric studies concerning CYN toxicity in different organs of tilapia have demonstrated an increase in the average nuclear diameter of hepatocytes in the liver (Gutiérrez‐Praena et al, ; Guzmán‐Guillén et al, ). However, for the kidney, contradictory results have been described, showing decreased cross‐sections of proximal and distal convoluted tubules (DCT) in fish exposed to pure CYN by oral and i.p.…”