Does the phycotoxin Okadaic acid cause oxidative stress damages and histological alterations to seabream (Sparus aurata)?

Okadaic Acid (OA) is a marine toxin responsible for DSP (Diarrheic Shellfish Poisoning) in humans produced by dinoflagellate. The genotoxic and cytotoxic effects of OA have been well reported in mammalian experimental animals and in vitro cultured cells. However, there are no available investigations regarding the involvement of the oxidative stress pathways in OA toxicity, especially on aquatic animals such as fish. In this context, we aimed in the present work to demonstrate whether OA (7.5 µg/ml) induces oxidative stress and histopathological damages in the fish species Sparus aurata under short term exposure (2 h, 4 h and 24 h). To this end, we have assessed lipid peroxidation and anti-oxidative stress response in liver tissue, and finally ultrastructural changes were investigated in hepatic and gills tissues. Our results clearly showed that OA induced significant enhancement in all tested parameters in a time dependent manner and seems to be a strong inducer of oxidative stress in aquatic animals. The data of the present study indicate also that histology is a successful tool to reveal OA impact on liver and gill tissues of Sparus aurata since the animal showed vascular dilation and hepatocellular membrane disintegration in liver and hypertrophy in secondary lamellae and necrotic aspect in the primary lamellae in gill tissue.

Circadian variation of isoniazid pharmacokinetics in mice.

INTRODUCTION: This study is designed to investigate whether the pharmacokinetics of the antituberculous agent isoniazid (INH) varied according to the circadian dosing-time. METHODS: A total of 168 male mice aged 10 weeks and synchronized for 3 weeks to 12h light and 12h dark were used. A single INH (100mg/kg) dose was administered by intraperitonal (i.p.) route at either of the four different circadian stages (1, 7, 13 and 19h after light onset, HALO). At each circadian stage, blood samples were withdrawn at 0, 0.1, 0.2, 0.4, 1, 1.3, 2, 2.5, 4, 5, 6.3, 8, 24 and 48h following drug injection. The pharmacokinetics parameters (AUC0-∞, Ke, Cmax, T 1/2, ClT and Vd) were calculated for each circadian-time. RESULTS: There were relevant differences in Cmax between the four circadian groups (p<0.005), maximum and minimum Cmax were obtained when INH was injected at 1 HALO (490mgL-1) and at 7 HALO (270mgL-1) respectively. AUC0-∞ also varied significantly according to the circadian-time of injection (2093mgL-1h-1 at 1 HALO vs 759mgL-1h-1 at 7 HALO) (p<0.05). The highest and lowest mean values of plasma clearance (Cl) were observed at 7 HALO (0.22Lh-1kg-1) and 1 HALO (0.13Lh-1kg-1) respectively (p<0.05). The Cosinor analysis showed a circadian rhythm in different pharmacokinetic parameters. Cmax and AUC0-∞ have a significant circadian rhythm with an acrophase located at 2.64 HALO±0.21h (the beginning of the rest span) (p<0.001), whereas ClT and Vd showed a significant circadian rhythm with an acrophase located respectively at 7.4 HALO and at 8.66 HALO (the second half of the rest span) (p<0.001). CONCLUSION: Plasma INH chronopharmacokinetics might be involved in the mechanism of circadian variation of toxicity since the time of optimal tolerance to INH corresponds to that of the lowest Cmax and AUC0-∞ and the highest ClT occured when this drug injected in the second half of light-rest phase (7 HALO).

Circadian variation in murine hepatotoxicity to the antituberculosis agent «Isoniazide¼.

The circadian time is an important process affecting both pharmacokinetics and pharmacodynamics of drugs. Consequently, the desired and/or undesired effects vary according to the time of drug administration in the 24 h scale. This study investigates whether the toxicity in liver as well as oxidative stress varies according to the circadian dosing-time of isoniazid (INH) in mice. A potentially toxic INH dose (120 mg/kg) was injected by i.p. route to different groups of animals at three different circadian times: 1, 9, and 17 Zeitgeber time (ZT). INH administration at 1 ZT resulted in a maximum hepatotoxicity assessed by the significant increase in both serum transaminase (ALAT: alanine aminotransferase) and (ASAT: aspartate aminotransferase) and antioxidant enzyme activities (catalase: CAT and superoxide dismutase: SOD). The highest malondialdehyde (MDA) level indicating an induction of lipid peroxidation resulting in oxidative damage was also observed at 1 ZT. Liver histopathology from INH groups at 9 ZT and at 1 ZT showed moderate to severe cytoplasma vacuolation, hepatocyte hypertrophy, ballooning, and necrosis. The circadian variation in INH toxicity may help realize a chronotherapy protocol in humans based on the selection of the best time associated to optimal tolerance or least side effects.

Circadian-time dependent tolerance and haematological toxicity to isoniazid in murine.

INTRODUCTION: Isoniazid (INH) is a widely used drug in the prophylaxis and treatment of tuberculosis. In the present study, isoniazid (INH)-induced toxicity was investigated according to the dosing-time in the 24-h scale in mice. METHODS: Two studies were carried out on a total of 180 male Swiss mice synchronized for 3 weeks to 12-hour light (rest) and 12-hour dark (activity) cycle (L/D: 12/12). In the first study a potentially lethal dose of INH (180 mg/kg) was administered by intraperitoneal (i.p.) route at six different circadian-times: 1, 5, 9, 13, 17 and 21 hours after light onset (HALO). In the second one, a sublethal dose (120 mg/kg) was administered at three circadian-times (1, 9 and 17 HALO) in order to evaluate the variation of haematological toxicity. Rectal temperature, body weight loss, survival (study 1) and complete cell count (study 2) were determined as toxicity endpoints. The Cosinor and ANOVA methods were used for the data statistical analysis. RESULTS: The Cosinor analysis of rectal temperature time series prior to treatment validated a circadian rhythm, which demonstrates that mice were well synchronized. Following INH injection, rectal temperature increased in all the six circadian stages at days 2 and 3. Body weight loss varied from -12% at 1 HALO to -7% at 13 HALO (P<0.001). The 24-h mean of mortality induced by INH was 38%. Such lethal toxicity varied according to the circadian dosing-time. Maximum (60%) and minimum (20%) survival rates were observed when INH was administered at 9 and 1 HALO respectively. The highest survival time (25 days) occurred when INH was injected at 9 HALO while the lowest survival time (7 days) occurred when INH was given at 1 HALO. The decrease of haematological variables (cytopenia) was dependent on the circadian dosing-time (P<0.001). The least haematological toxicity illustrated by leukopenia index, anaemia and thrombocytopenia was observed in the middle of the second half of the light-rest phase (9 HALO).

Lead accumulation pattern and molecular biomarkers of oxidative stress in seabream (Sparus aurata) under short-term metal treatment.

The present work aimed to look at the distribution and accumulation pattern of Lead (Pb) within the fish body after 2 h, 4 h and 24 h of waterborne exposure to the metal at 0.75 mg/L. Tests of lead acute toxicity and bioaccumulation were performed in the common fish species Sparus aurata. In our study, we assessed the oxidative stress damages extent after 2 h, 4 h and 24 h of exposure to lead using the enzymatic stress biomarkers: Superoxide Dismutase (SOD), Catalase (CAT) and Gluthathione (GSH). The lipid peroxidation (LPO) was also investigated by dosing Malondyhaldéhyde (MDA) quantities in the liver tissue. The acute neurotoxicity of Pb was evaluated in the dorsal white muscle using the Acethylcholenesterase (AchE) activity. The liver tissue accumulates preferentially the metal, followed by the intestines, the gills and finally the dorsal muscle. The antioxidant response failed to prevent the lipid peroxidation and the neurotoxic effect of lead after 24 h of exposure.

Effect of acute cadmium exposure on metal accumulation and oxidative stress biomarkers of Sparus aurata.

Cadmium (Cd) is a non-essential metal which could be toxic in traces for aquatic species. Increasing Cd concentrations in sea water is mainly related to waste waters provided from growing industrial and agricultural activities. The present study investigated the accumulation of Cd (0.5mg/L) in different tissues of Sparus aurata under a short term exposure (2, 4 and 24h) using the atomic absorption. This work investigated also the impact of the metal on oxidative stress biomarkers and acetyl cholinesterase activity (AchE). Our results showed that Cd accumulation in different tissues depends largely on the length of the exposure period to the metal. Indeed, the highest concentrations were obtained after 24h. Cd accumulation in tissues was in the following order: intestines > liver > gills > dorsal muscle. Cadmium administration increased significantly catalase activity (CAT), glutathione level (GSH) and malondialdehyde production (MDA) after 24h of exposure. In contrast, AchE activity was decreased after the same period of exposure to the metal. There were no significant changes in oxidative stress biomarkers after 2 and 4h of exposure, except for superoxide dismutase (SOD) activity which attained the highest level after 4h. These results suggest that short-term exposure of Sparus aurata to Cd (0.5mg/L) induced an important metal accumulation in intestine and a notable oxidative stress response.