The acute toxicity effects of hexavalent chromium in antioxidant system and gonad development to male clam Geloina coaxans

Histopathological alterations in the gonads of wild white clams Dosinia ponderosa inhabiting a former copper mine locality in the Gulf of California

OBJECTIVE

Prolonged exposure to heavy metals, such as Pb, Hg, or Cu, has multiple adverse effects on marine organisms at the cellular, physiological, and population levels. Bivalves' histopathology provides a sensitive biomarker of pollutant-induced stress and environmental health. Gonad tissue deterioration is of particular concern, as it affects the reproductive success of a species. This study aimed to examine the histopathological alterations caused by metal exposure in the gonad of the white clam Dosinia ponderosa.

METHODS

Organisms were sampled from three locations in the Gulf of California: Santa Rosalia (SR), a former Cu mining town; San Lucas beach (SL), a nearby site influenced by pollution; and Escondida beach (EB), which served as a control site. Histological and histochemical stains were used, and the prevalence and intensity level of each alteration were calculated.

RESULT

The prevalence of alterations was higher in the ovaries of SR clams (92% compared to 60% in SL clams and 32.7% in EB clams), during spawning (91.4% compared to 20% in SL clams and 4.7% in EB clams), and in winter (93.5% compared to 30% in SL clams and 17.4% in EB clams).

CONCLUSION

These findings suggest a significant deterioration in the gonads of white clams from SR, probably linked to the chronic exposure to high concentrations of Cu and possibly other heavy metals; hence, the reproductive health of the clams is likely compromised.

Potential arsenic-chromium-lead Co-contamination in the hilly terrain of Arunachal Pradesh, north-eastern India: Genesis and health perspective

In the recent times, multi-metal co-contamination in the groundwater of various parts of the globe has emerged as a challenging environmental health problems. While arsenic (As) has been reported with high fluoride and at times with uranium; and Cr & Pb are also found in aquifers under high anthropogenic impacts. The present work probably for the first time traces the As-Cr-Pb co-contamination in the pristine aquifers of a hilly terrain that are under relatively less stress from the anthropogenic activities. Based on the analyses of twenty-two (n = 22) groundwater (GW) samples and six (n = 6) sediment samples, it was found that Cr being leached from the natural sources as evident from 100% of samples with dissolve Cr exceeding the prescribed drinking water limit. Generic plots suggests rock-water interaction as the major hydrogeological processes with mixed Ca²⁺-Na⁺-HCO₃^- type water. Wide range of pH suggests localized human interferences, as well as indicative of both calcite and silicate weathering processes. In general water samples were found high only with Cr and Fe, however all sediment samples were found to contain As-Cr-Pb. This implies that the groundwater is under-risk of co-contamination of highly toxic trio of As-Cr-Pb. Multivariate analyses indicate that the changing pH as the causative factor for Cr leaching into the groundwater. This is a new finding for a pristine hilly aquifers, and we suspect such condition may also be present in other parts of globe, and thus precautionary investigations are needed to prevent this catastrophic situation to arise, and to alert the community in advance.

Transcriptional Responses as Biomarkers of General Toxicity: A Systematic Review and Meta-analysis on Metal-Exposed Bivalves

Through a systematic review and a series of meta-analyses, we evaluated the general responsiveness of putative transcriptional biomarkers of general toxicity and chemical stress. We targeted metal exposures performed on bivalves under controlled laboratory conditions and selected six transcripts associated with general toxicity for evaluation: catalase, glutathione-S-transferase, heat shock proteins 70 and 90, metallothionein, and superoxide dismutase. Transcriptional responses (n = 396) were extracted from published scientific articles (k = 22) and converted to log response ratios (lnRRs). By estimating toxic units, we normalized different metal exposures to a common scale, as a proxy of concentration. Using Bayesian hierarchical random effect models, we then tested the effects of metal exposure on lnRR, both for metal exposure in general and in meta-regressions using toxic unit and exposure time as independent variables. Corresponding analyses were also repeated with transcript and tissue as additional moderators. Observed patterns were similar for general and for transcript- and tissue-specific responses. The expected overall response to arbitrary metal exposure was an lnRR of 0.50, corresponding to a 65% increase relative to a nonexposed control. However, when accounting for publication bias, the estimated "true" response showed no such effect. Furthermore, expected response magnitude increased slightly with exposure time, but there was little support for general monotonic concentration dependence with regard to toxic unit. Altogether, the present study reveals potential limitations that need consideration prior to applying the selected transcripts as biomarkers in environmental risk assessment. Environ Toxicol Chem 2023;42:628-641. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Altered Expression of Protamine-like and Their DNA Binding Induced by Cr(VI): A Possible Risk to Spermatogenesis?

Chromium (VI) is the most dangerous oxidation state among the stable forms of chromium. In this work, we evaluated the effect of exposing Mytilus galloprovincialis for 24 h to 1, 10, and 100 nM chromium (VI) on the properties of Protamine-like (PLs) and their gene levels in the gonads. Specifically, we analyzed, by AU-PAGE and SDS-PAGE, PLs extracted from unexposed and exposed mussels. In addition, via EMSA, we evaluated the ability of PLs to bind DNA and also verified their potential to protect DNA from oxidative damage. Finally, we assessed possible alterations in gonadal expression of mt10, hsp70, and genes encoding for PLs-II/PL-IV and PL-III. We found that for all experimental approaches the most relevant alterations occurred after exposure to 1 nM Cr(VI). In particular, a comigration of PL-II with PL-III was observed by SDS-PAGE; and a reduced ability of PLs to bind and protect DNA from oxidative damage was recorded. This dose of chromium (VI) exposure was also the one that produced the greatest alterations in the expression of both mt10 and PL-II/PL-IV encoding genes. All of these changes suggest that this dose of chromium (VI) exposure could affect the reproductive health of Mytilus galloprovincialis.

Ipomoea staphylina Attenuates Potassium Dichromate-Induced Nephrotoxicity in Wistar Rats via Antioxidant and Antiapoptotic Effects

Occupational and environmental exposure to chromium compounds leads to nephrotoxicity to humans and animals due to the overproduction of ROS. Our study was aimed to demonstrate the shielding effect of hydroethanolic extract of Ipomoea staphylina (HEIS) bark on male Wistar rats challenged with potassium dichromate (K₂Cr₂O₇). Division of animals was done in 4 groups' viz., normal control, K₂Cr₂O₇ control, K₂Cr₂O₇+HEIS (100 mg/kg), and K₂Cr₂O₇+HEIS (200 mg/kg). Except for the normal control group, other groups were challenged with a single dose (subcutaneous) of K₂Cr₂O₇ (15 mg/kg) and then treated with HEIS (100 and 200 mg/kg) for 1 week. It was observed that animals treated with K₂Cr₂O₇ showed a notable increase in serum creatinine, blood urea, and BUN and dwindles in protein level. These changes were significantly reversed after a 1-week treatment with HEIS (100 and 200 mg/kg). Moreover, HEIS (100 and 200 mg/kg) showed a remarkable improvement in the activity of antioxidant enzymes (GPx, CAT, and SOD) and decreased the levels of TNF-α and IL-1β in the kidney. Furthermore, treatment with HEIS (100 and 200 mg/kg) notably decreased the activity of caspase-3 and improved the level of HO-1 especially in the K₂Cr₂O₇+ HEIS (200 mg/kg) group. Also, the histopathological study of the kidney supported the protective effects of HEIS. Hence, HEIS bark holds a notable protective effect against K₂Cr₂O₇-induced nephrotoxicity in rats.