Jinling Cao

Effects of fluoride on liver apoptosis and Bcl-2, Bax protein expression in freshwater teleost, Cyprinus carpio

Fish take up fluoride directly from water and are the target organisms for fluoride pollution in the aquatic ecosystems. This study was conducted to evaluate oxidative stress, histopathological changes, apoptosis and Bcl-2, Bax expression in the livers of the common carp (Cyprinus carpio) chronically exposed to fluoride. Our results showed that after 90 d of exposure, the inhibition of SOD, GSH activities and a dose-dependent stimulation of MDA levels in the liver tissues indicated that fluoride caused oxidative stress in the fish. Microscopic examinations showed that damages to the liver tissues and cell organelles in the liver tissues increased with exposure concentration. A positive correlation was observed between the apoptosis index and fluoride levels in the livers (r=0.995). There was a negative correlation between the fluoride concentration of water and the expression of Bcl-2, Bcl-2/Bax (r=-0.98, r=-0.96). A positive correlation was showed between the fluoride concentration of water and the expression of Bax (r=0.96) after 90 d of exposure. Our results suggested that the common carp could tolerate relatively high levels of fluoride but adverse effects of fluoride occurred in the livers of the fish after 90 d of exposure. The apoptosis of liver cells had an important causative role in the process of fluoride-induced pathological changes of liver.

Tissue distributions of fluoride and its toxicity in the gills of a freshwater teleost, Cyprinus carpio

Fish take up fluoride directly from water and are susceptible to fluoride contamination of their environment. In this study, we examined the tissue distributions of fluoride and its toxicity in the gills of the common carp (Cyprinus carpio) chronically exposed to fluoride. Carp were exposed to a range of aqueous fluoride (35-124 mg/L) and sampled at 30, 60 and 90 days. The accumulation of fluoride in the tissues increased with the level and duration of exposure. Steady state was not achieved under the experimental conditions. The gills accumulated the highest levels of fluoride followed by the liver>brain>kidney>muscle>intestine. A dose-dependent inhibition was observed for the enzyme activities of Na(+)-K(+)-ATPase and Ca(2+)-ATPase in the gills after the fish were exposed for 90 days. Also, accumulation of fluoride was associated with the inhibition of superoxide dismutase (SOD) activities and a dose-dependent stimulation of malondialdehyde (MDA) levels in the gill tissues, suggesting that fluoride promoted oxidative stress in the fish. Microscopic examinations revealed injuries to gill tissues and chloride cells, with the severity of injury increasing with exposure concentration. These results suggest that chronic exposure to elevated concentrations of fluoride may induce toxicity in the common carp.

Protective properties of sesamin against fluoride-induced oxidative stress and apoptosis in kidney of carp (Cyprinus carpio) via JNK signaling pathway.

Sesamin, a major lignan derived from sesame seeds, has been reported to have many benefits and medicinal properties. However, its protective effects against fluoride-induced injury in kidney of fish have not been clarified. Previously we found that fluoride exposure caused damage and apoptosis in the kidneys of the common carp, Cyprinus carpio. In this study, the effects of sesamin on renal oxidative stress and apoptosis in fluoride-exposed fish were determined. The results showed that sesamin alleviated significantly fluoride-induced renal damage and apoptosis of carp in a dose-dependent manner, indicated by the histopathological examination and ultrastructural observation. Moreover, treatment with sesamin also inhibited significantly fluoride-induced remarkable enhancement of reactive oxygen species (ROS) production and oxidative stress, such as the increase of lipid peroxidation level and the depletion of intracellular reduced glutathione (GSH) level in kidney. To explore the underlying mechanisms of sesamin action, we found that activities of caspase-3 were notably inhibited by treatment with sesamin in the kidney of fluoride-exposed fish. Sesamin decreased the levels of p-JNK protein in kidney, which in turn inactivated pro-apoptotic signaling events by restoring the balance between mitochondrial pro- and anti-apoptotic Bcl-2 and Bax proteins and by decreasing the release of mitochondrial cytochrome c in kidney of fluoride-exposed fish. JNK was also involved in the mitochondrial extrinsic apoptotic pathways of sesamin effects against fluoride-induced renal injury by regulating the levels of p-c-Jun, necrosis factor-alpha (TNF-α) and Bak proteins. These findings indicated that sesamin could protect kidney against fluoride-induced apoptosis by the oxidative stress downstream-mediated change in the inactivation of JNK signaling pathway. Taken together, sesamin plays an important role in maintaining renal health and preventing kidney from toxic damage induced by fluoride.

The chronic effects of lignin-derived bisphenol and bisphenol A in Japanese medaka Oryzias latipes.

One of the ultimate goals of green chemistry is to produce greener and more environmentally friendly chemicals to replace the existing toxic chemicals. In this study, Japanese medaka were exposed to 1.5mg/L of bisphenol A or lignin-derived bisphenol for 60 days, and the expressions of various biochemical markers, effects on reproduction, and histopathology were evaluated. The results showed that concentrations of liver vitellogenin of LD-BP exposed males were approximately 125% higher compared to the control males. Total number of eggs from the BPA and LD-BP exposed fish was approximately 47% (p<0.001) and 25% (p<0.05) less than the control fish, respectively. Total number of brood was lower from the BPA (46%, p<0.05) and LD-BP (17%, p<0.05) exposed fish than that of the control fish. Relative to the control fish, catalase and glutathione-S-transferase were significantly affected by the two chemicals in all tested tissues. BPA and LD-BP caused lipid peroxidation in all the tested tissues. Furthermore, acetylcholinesterase and α-glucosidase activity were significantly inhibited. Histopathological analysis showed that both the testis and ovary were mildly damaged by both chemicals. LD-BP affected medaka slightly more severe than BPA except on the reproduction, which was most likely due to different uptake, translocation, binding to targets and metabolism. Our results demonstrated that chronic exposure to both chemicals caused several adverse effects to medaka. Further research on the toxicity of LD-BP to other aquatic organisms is needed before substitution of traditional BPA with LD-BP can be recommended.

Effects of fluoride on growth, body composition, and serum biochemical profile in a freshwater teleost, Cyprinus carpio.

Fluoride is ubiquitously distributed in natural waters. Elevated fluoride may cause histopathological changes and induce oxidative stress in the gills of the common carp (Cyprinus carpio). The present study further evaluates the effects of fluoride on growth performance, body composition, and biochemical measurements of C. carpio. The results showed that food intake, growth, serum osmolality, body composition, and biochemical measures in the blood were affected by fluoride. Weight gain rate and specific growth rate in the exposed fish decreased compared with those of the control fish. Levels of crude protein and crude lipids were reduced in the fluoride-exposed fish. The major ion levels in the sera of fluoride-exposed fish were severely disturbed, resulting in a lower osmolality. All the biochemical parameters measured in the blood were affected by the exposure to fluoride. Total protein, albumin, globulin, and glucose in fish exposed to 63.6 mg/L, 77.7 mg/L, and 124.4 mg/L were lower than those in the control fish. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were markedly increased in exposed fish compared with control. Taken together, the data showed that exposure to fluoride caused a suite of detrimental effects in C. carpio, which might lead to a decrease in growth and food utilization efficiency. The results of the present study indicated that high levels of fluoride could pose a threat to carp in the field.

Effects of fluoride and aluminum on expressions of StAR and P450scc of related steroidogenesis in guinea pigs' testis

A lot of studies have shown that fluoride and aluminum have toxic effect on male reproductive system, but the mechanism of which and the interaction between fluoride and aluminum is still unknown. This study investigated the effects of fluoride (NaF) or/and aluminum (AlCl3) on serum testosterone level, gene and protein expression levels of Steroidogenic Acute Regulatory Protein (StAR) and Cytochrome P450 cholesterol side chain cleavage enzyme (P450scc) in the testes of guinea pigs. Fifty-two guinea pigs were divided randomly into four groups (Control, HiF, HiAl and HiF + HiAl). Fluoride (150 mg NaF/L) or/and aluminum (300 mg AlCl3/L) were orally administrated to male guinea pigs for 13 weeks. The results showed that F and Al reduced number and elevated abnormal ratio of sperm. Meanwhile, the concentrations of serum testosterone in all experimental groups were decreased. P450scc protein expression was significantly reduced in all treatment groups, and StAR expression was decreased remarkably in HiF group and HiF + HiAl group. The levels of StAR mRNA in three groups were reduced by 53.9%, 21.4% and 33.4%, respectively, while the expressions of P450scc mRNA were reduced by 67.8%, 17.0% and 47.8%. Therefore, we concluded that F induced the reduction in testosterone and sperm amount, and thus in lower fertility, which might occur as a consequence of depressed StAR and P450scc mRNA expression. There were no synergistic effects between F and Al, instead, Al weakened the toxicity of F to some extents. The results indicated that Al had antagonism effects on F.

Fluoride-induced apoptosis and expressions of caspase proteins in the kidney of carp (Cyprinus carpio).

The study was conducted to investigate oxidative stress, apoptosis, and protein expressions of caspase‐3, 8, and 9 in kidney of the carp juveniles exposed to 0, 40, 80, 120, and 160 mg L−1 of fluoride (in the form of NaF) for 90 days. The results showed that dose‐ and time‐dependent decrease of SOD and GSH and dose‐ and time‐dependent increase of MDA were observed in the carp juveniles, which suggested that fluoride induced oxidative damage accompanied with morphological changes and significant apoptosis in fish exposed to fluoride, especially in the higher doses. Fluoride exposure also significantly elevated the protein expressions of caspase‐3, 8, and 9. In conclusion, these results indicate that chronic exposure to fluoride causes oxidative stress, damages the kidney structure, and results in renal apoptosis by caspase‐dependent pathway.

Maternal transfer and reproductive effects of Cr(VI) in Japanese medaka (Oryzias latipes) under acute and chronic exposures.

Maternal transfer of metals can be an important exposure route for animals. The maternal transfer of Cr and its effects on reproduction in fish are still largely unknown. In this study, Japanese medaka were exposed to a sublethal Cr(VI) concentration for 6 days (acute) and for 3 months (chronic). Chromium accumulation in the gonads, maternal transfer of Cr, and effects of Cr on the reproduction, histopathology and expressions of antioxidants in the gonads were evaluated. Both acute and chronic exposures resulted in significant Cr accumulation in gonads, eggs and larvae. In chronic Cr-exposed fish, approximately 61% of the Cr accumulated in the ovary was depurated by spawning during the first 3 days after exposure, suggesting that maternal transfer is a very important pathway for accumulation in offspring. The chronic exposure caused decreases in body weight, standard length, gonad weight, gonad-somatic index (GSI) and fecundity. The last of these was most severely affected: the total number of broods and eggs per female decreased by 57.1% and 75.9%, respectively. Moreover, egg weight and fertilization rate were also reduced (by approximately 20%) following chronic Cr(VI) exposure. Histopathological analyses showed that the Cr exposure resulted in the onset of follicular atresia and a reduction in the number of mature oocytes, along with a reduction in abundance of mature spermatozoa in testes. The GSH/GSSG ratio was greatly elevated after chronic Cr(VI) exposure, implying that GSH played a role in scavenging the reactive oxygen species generated by the reduction of Cr(VI) inside cells. This study provides evidence for the maternal transfer of Cr, highlights the importance of spawning in Cr depuration from the ovary, and demonstrates that chronic Cr(VI) exposure has serious impacts on reproduction in the Japanese medaka. Our results suggest that the issue of chronic Cr pollution deserves more attention than it has received to date.

Accumulation and effects of Cr(VI) in Japanese medaka (Oryzias latipes) during chronic dissolved and dietary exposures

Chromium (Cr) is an essential metal and a nutritional supplement for both human and agricultural uses. It is also a pollutant from a variety of industrial uses. These uses can lead to elevated Cr levels in aquatic environments, where it can enter and affect aquatic organisms. Its accumulation and subsequent effects in fish have received relatively little attention, especially for chronic exposure. In the present study, Japanese medaka were chronically exposed to dissolved or dietary Cr(VI) for 3 months. Cr accumulation in liver, gills, intestine, and brain was evaluated. Effects on the antioxidant system, nervous system (acetylcholinesterase, AChE), digestive system (α-glucosidase, α-Glu), and tissue histology (liver and gills) were also assessed. Cr accumulation was observed in the intestine and liver of fish exposed to Cr-contaminated brine shrimp. However, chronic dissolved Cr exposure led to significant Cr accumulation in all organs tested. Analysis of the subcellular distribution of Cr in medaka livers revealed that 37% of the Cr was present in the heat stable protein fraction. The dissolved Cr exposure had pronounced effects on the antioxidant system in the liver, with an elevated ratio of reduced glutathione/oxidized glutathione (GSH/GSSG) and decreases in GSH and glutathione S-transferase (GST). The α-Glu activity in the intestine was significantly inhibited. In addition, Cr exposure caused histopathological alterations in the gills and liver. In general, the effects of dietary Cr were relatively minor, possible due to the much lower accumulation in the fish. Our results imply that Japanese medaka accumulate Cr mainly via uptake of dissolved Cr(VI).

Effects of sodium fluoride on MAPKs signaling pathway in the gills of a freshwater teleost, Cyprinus carpio.

Exposure to elevated levels of fluoride can cause a variety of adverse effects in fish. Previously we showed that fluoride causes injuries and apoptosis in the gills of Cyprinus carpio. In this study, the effects of fluoride on caspase-3 activity and on accumulation of proteins in the MAPKs pathways were evaluated using Western blotting and immunohistochemistry methods in vivo and in vitro. In vivo experiments showed that the caspase-3 activity increased with fluoride exposure level in a dose-dependent pattern Western blotting and immunohistochemistry results indicated that ERK relative activation tended to decrease as a function of fluoride exposure concentration. In contrast, relative activation of JNK increased with fluoride exposure level. Fluoride exposure did not appear to affect p38 activation. Furthermore, pretreatment of branchial cells with MAPK-specific inhibitors effectively prevented JNK induction and ERK inhibition, respectively, as well as reversed caspase-3 activity in fluoride-treated branchial cells. Our results indicate that activation of JNK and inactivation of ERK were caused by increased ROS and decreased antioxidant capacity in the gills of chronically exposed C. carpio described previously, which eventually caused the observed apoptosis in the fluoride-exposed gills and cells in C. carpio. JNK activation and ERK inactivation mechanism play a crucial role in gill impairment induced by chronic fluorosis. These findings contribute to a better understanding of the initial molecular and cellular events in the gill of fish chronically exposed to fluoride.