Attenuation of Lead-Induced Neurotoxicity by Omega-3 Fatty Acid in Rats

An insight on the plausible biological and non-biological detoxification of heavy metals in tannery waste: A comprehensive review

A key challenge for the tannery industries is the volume of tannery waste water (TWW) generated during the processing of leather, releasing various forms of toxic heavy metals resulting in uncontrolled discharge of tannery waste (TW) into the environment leading to pollution. The pollutants in TW includes heavy metals such as chromium (Cr), cadmium (Cd), lead (Pb) etc, when discharged above the permissible limit causes ill effects on humans. Therefore, several researchers have reported the application of biological and non-biological methods for the removal of pollutants in TW. This review provides insights on the global scenario of tannery industries and the harmful effects of heavy metal generated by tannery industry on micro and macroorganisms of the various ecological niches. It also provides information on the process, advantages and disadvantages of non-biological methods such as electrochemical oxidation, advanced oxidation processes, photon assisted catalytic remediation, adsorption and membrane technology. The various biological methods emphasised includes strategies such as constructed wetland, vermitechnology, phytoremediation, bioaugmentation, quorum sensing and biofilm in the remediation of heavy metals from tannery wastewater (TWW) with special emphasize on chromium.

Intervention effect of Lycium barbarum polysaccharide on lead-induced kidney injury mice and its mechanism: A study based on the PI3K/Akt/mTOR signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional medicinal application of Lycium barbarum is centered on the improvement of eyesight, as well as the nourishment of liver and kidney functions. Lycium barbarum polysaccharide (LBP), serving as the principal active constituent of Lycium barbarum, has been identified as the main contributor to these beneficial effects. Previous studies have indicated that Lycium barbarum polysaccharide exhibits a renoprotective effect against lead-induced injury, but its mechanism and efficacy remain unclear.

AIM OF THE STUDY

The objective of this study was to examine the effectiveness of LBP in preventing lead-induced renal injury and investigate both the toxic mechanism of lead-induced renal injury and the efficacy mechanism of LBP against it, with a focus on the PI3K/AKT/mTOR signaling pathway.

MATERIALS AND METHODS

The drug effect and mechanism of LBP on lead-induced kidney injury were investigated by administering positive drugs and LBP to mice with established lead-induced kidney injury.

RESULTS

The renal function of mice with lead-induced renal injury was significantly restored, renal tissue lesions and renal mitochondrial damage were delayed, a disorder of hematological parameters induced by lead was improved, the increase of lead-induced renal index was reduced, and the body weight of mice with lead-induced renal injury was increased by the LBP intervention, as revealed by the results of pharmacodynamic experiments. Based on PI3K /AKT /mTOR signaling pathway, the toxic mechanism of lead-induced kidney injury and the pharmacodynamic mechanism of LBP against lead-induced kidney injury were studied. The results showed that lead could activate the TLR4 receptor, and then activate PI3K /AKT /mTOR signaling pathway, inhibit autophagy of kidney tissue cells, and enhance apoptosis of kidney tissue cells to induce kidney injury; LBP inhibits the activation of TLR4 receptor, which in turn inhibits the PI3K/AKT/mTOR signaling pathway, enhances the autophagy of kidney tissue cells, reduces the apoptosis of kidney tissues, and delays lead-induced kidney injury.

Early-Life Lead Exposure: Risks and Neurotoxic Consequences

BACKGROUND

Lead (Pb) does not have any biological function in a human, and it is likely no safe level of Pb in the human body. The Pb exposure impacts are a global concern for their potential neurotoxic consequences. Despite decreasing both the environmental Pb levels and the average blood Pb levels in the survey populations, the lifetime redistribution from the tissues-stored Pb still poses neurotoxic risks from the low-level exposure in later life. The growing fetus and children hold their innate high-susceptible to these Pb-induced neurodevelopmental and neurobehavioral effects.

OBJECTIVE

This article aims to evaluate cumulative studies and insights on the topic of Pb neurotoxicology while assessing the emerging trends in the field.

RESULTS

The Pb-induced neurochemical and neuro-immunological mechanisms are likely responsible for the high-level Pb exposure with the neurodevelopmental and neurobehavioral impacts at the initial stages. Early-life Pb exposure can still produce neurodegenerative consequences in later life due to the altered epigenetic imprints and the ongoing endogenous Pb exposure. Several mechanisms contribute to the Pb-induced neurotoxic impacts, including the direct neurochemical effects, the induction of oxidative stress and inflammation through immunologic activations, and epigenetic alterations. Furthermore, the individual nutritional status, such as macro-, micro-, or antioxidant nutrients, can significantly influence the neurotoxic impacts even at low-level exposure to Pb.

CONCLUSION

The prevention of early-life Pb exposure is, therefore, the critical determinant for alleviating various Pb-induced neurotoxic impacts across the different age groups.

Role of Nitric Oxide, TNF-α and Caspase-3 in Lead Acetate-Exposed Rats Pretreated with Aqueous Rosmarinus officinalis Leaf Extract

Lead (Pb) toxicity is a worldwide significant public health challenge causing several neurological disorders. Reports indicate that plants rich in antioxidants, such as Rosmarinus officinalis (RO), can counteract Pb accumulation and its toxicity in the brain. Due to a dearth of literature evidence demonstrating the protective activity of RO against Pb toxicity, this study investigated such activity in Wistar rats. Thirty-six Wistar rats were allocated into six groups (n=6), namely I (control), II (lead acetate [Pb]; 100 mg/kg b.w.), III (100 mg/kg of RO and 100 mg/kg of Pb), IV (200 mg/kg of RO and 100 mg/kg of Pb), V (100 mg/kg b.w. of RO) and VI (200 mg/kg b.w. of RO). After 28 days, neurobehavioural, antioxidant, lipid peroxidation, apoptotic and inflammatory activities as well as the histology of the cerebellum were evaluated. Body weight, locomotion and exploration as well as antioxidant enzymes were significantly (p < 0.05) decreased in Pb-exposed rats when compared to control. Conversely, lipid peroxidation, nitric oxide, tumour necrosis factor-alpha and caspase-3 activities were significantly (p < 0.05) upregulated in the Pb-exposed rats when compared to control. These parameters were, however, significantly (p<0.05) attenuated in the RO-pretreated rats when compared to Pb-exposed rats. Cerebellar histology of the Pb-exposed rats showed severe degeneration of the Purkinje cells whereas the RO-pretreated rats showed better cerebellar architecture. These findings demonstrate that the neuroprotective activity of RO is facilitated via its effective antioxidant, anti-inflammatory and anti-apoptotic effects.

Curcumin-loaded cockle shell-derived calcium carbonate nanoparticles ameliorates lead-induced neurotoxicity in rats via attenuation of oxidative stress

A substantial global health burden is associated with neurotoxicity caused by lead (Pb) exposure and the common mechanism of this toxicity is mainly via oxidative damage. Curcumin has remarkable pharmacological activities but remains clinically constrained due to its poor bioavailability when orally administered. Currently, cockle shell-derived calcium carbonate nanoparticle (CSCaCO3NP) is gaining more acceptance in nanomedicine as a nanocarrier to various therapeutics. This study aimed at investigating the ameliorative effect of curcumin-loaded CSCaCO3NP (Cur-CSCaCO3NP) on lead-induced neurotoxicity in rats. A total of 36 male Sprague-Dawley rats were randomly assigned into five groups. Each group consists of 6 rats apart from the control group which consists of 12 rats. During the 4 weeks induction phase, all rats received a flat dose of 50 mg/kg of lead while the control group received normal saline. The treatment phase lasted for 4 weeks, and all rats received various doses of treatments as follows: group C (Cur 100) received 100 mg/kg of curcumin, group D (Cur-CSCaCO3NP 50) received 50 mg/kg of Cur-CSCaCO3NP, and group E (Cur-CSCaCO3NP 100) received 100 mg/kg of Cur-CSCaCO3NP. The motor function test was carried out using the horizontal bar method. The cerebral and cerebellar oxidative biomarker levels were estimated using ELISA and enzyme assay kits. Lead-administered rats revealed a significant decrease in motor scores and SOD activities with a resultant increase in MDA levels. Furthermore, marked cellular death of the cerebral and cerebellar cortex was observed. Conversely, treatment with Cur-CSCaCO3NP demonstrated enhanced ameliorative effects when compared with free curcumin treatment by significantly reversing the aforementioned alterations caused by lead. Thus, CSCaCO3NP enhanced the efficacy of curcumin by ameliorating the lead-induced neurotoxicity via enhanced attenuation of oxidative stress.

Protecting Effects of N-acetyl Cysteine Supplementation Against Lead and Cadmium-Induced Brain Toxicity in Rat Models

We aimed to investigate mitigating effects of N-acetylcysteine (NAC) on the oxidative stress, apoptosis and Parkinson's disease (PD)-related genes in the brain tissue of male rats exposed to continuous doses of cadmium and lead. Rats were randomly divided into five groups, including G1 (control), G2 (continuous dose of Cd), G3 (continuous dose of Pb), G4 (continuous dose of Cd + NAC), and G5 (continuous dose of Pb + NAC). Biomarkers of oxidative stress, malondialdehyde (MDA), and total antioxidant capacity (TAC) were measured. Expression of PD- and apoptosis-related genes was considered using RT-PCR. Chronic exposure to these heavy metals was associated with accumulation of Pb and Cd in the brain and blood and caused severe morphological changes in the brain, as well as decreased body and brain weights. Continuous exposure to Cd and Pb significantly decreased TAC content and SOD expression but increased MDA level in the brain tissues (P < 0.001). A significant increase was observed in expression of PD-related genes, Parkin, Pink1, LRRK2, SNCA, and Caspase-3 in the brain tissues following exposure to Cd and Pb. Pb exhibited stronger toxicity on the brain tissue compared to Cd. NAC supplementation not only improved morphological changes, but also compensated antioxidant capacity and expression of apoptosis- and PD-related genes in the brain tissues when compared to rats exposed to Pb and Cd alone. Chronic exposure to Pb and Cd is strongly associated with accumulation of these heavy metals in the brain, morphological changes, antioxidants depletion, oxidative stress, and brain cells apoptosis. Changes in expression of PD-related genes indicate the higher risk of PD among individuals who are chronically exposed to these heavy metals. NAC can protect brain tissue against Pb and Cd toxicity by elevating antioxidants capacity, mitigating oxidative stress, apoptosis, and down-regulating of PD-related genes.

Phytochemical: a treatment option for heavy metal induced neurotoxicity

Heavy metals are known to be carcinogenic, mutagenic, and teratogenic. Some heavy metals are necessary while present in the growing medium in moderate concentrations known to be essential heavy metals as they required for the body functioning as a nutrient. But there are some unwanted metals and are also toxic to the environment and create a harmful impact on the body, which termed to be non-essential heavy metals. Upon exposure, the heavy metals decrease the major antioxidants of cells and enzymes with the thiol group and affect cell division, proliferation, and apoptosis. It interacts with the DNA repair mechanism and initiates the production of reactive oxygen species (ROS). It subsequently binds to the mitochondria and may inhibit respiratory and oxidative phosphorylation in even low concentrations. This mechanism leads to damage antioxidant repair mechanism of neuronal cells and turns into neurotoxicity. Now, phytochemicals have led to good practices in the health system. Phytochemicals that are present in the fruits and herbs can preserve upon free radical damage. Thus, this review paper summarized various phytochemicals which can be utilized as a treatment option to reverse the effect of the toxicity caused by the ingestion of heavy metals in our body through various environmental or lifestyles ways.

Exposure of metal toxicity in Alzheimer’s disease: An extensive review

Metals serve important roles in the human body, including the maintenance of cell structure and the regulation of gene expression, the antioxidant response, and neurotransmission. High metal uptake in the nervous system is harmful because it can cause oxidative stress, disrupt mitochondrial function, and impair the activity of various enzymes. Metal accumulation can cause lifelong deterioration, including severe neurological problems. There is a strong association between accidental metal exposure and various neurodegenerative disorders, including Alzheimer’s disease (AD), the most common form of dementia that causes degeneration in the aged. Chronic exposure to various metals is a well-known environmental risk factor that has become more widespread due to the rapid pace at which human activities are releasing large amounts of metals into the environment. Consequently, humans are exposed to both biometals and heavy metals, affecting metal homeostasis at molecular and biological levels. This review highlights how these metals affect brain physiology and immunity and their roles in creating harmful proteins such as β-amyloid and tau in AD. In addition, we address findings that confirm the disruption of immune-related pathways as a significant toxicity mechanism through which metals may contribute to AD.

Multibiomarker approach to assess the magnitude of occupational exposure and effects induced by a mixture of metals

Metals and metalloids including lead (Pb), arsenic (As) and manganese (Mn) can occur as mixtures in occupational contexts, such as mines. These chemicals are all known to be neurotoxic and provoke changes in heme metabolism also known to induce neurotoxicity. The objective of this work was to propose a multi-biomarker (BM) methodology to screen subjects exposed to the mixture of Pb, As and Mn and assess the severity of their exposure/effects, in an individual basis. The urinary levels of the metals, dela-aminolevulinic acid (ALA) and porphyrins were determined in Portuguese miners and in a control group. The combination of Pb and As urinary levels had the highest capability to identify subjects occupationally exposed to this mixture in mines, as evaluated through Receiver Operating Characteristic (ROC) (A = 98.2%; p < 0.05), allowing that 94.2% of 86 studied subjects were properly identified and the generation of an equation indicating the odd of a subject be considered as exposed to the metal mixture. The combination of urinary ALA and porphyrins revealed to be best one to be applied in the assessment of subjects with high, intermediate, and low magnitudes of exposure/effects, with 95.7% of 46 miners classified correctly according to their severity sub-group and allowing to generate equations, which can be applied in new subjects. The proposed methodology showed a satisfactory performance, evaluating in an integrated manner the magnitude of exposure/effects of the exposed workers, may contributing to improve the control of their health.

Neuroprotective role of luteolin against lead acetate-induced cortical damage in rats

Luteolin (LUT) is a glycosylated flavonoid compound that has multiple beneficial pharmacological and biological impacts. The current investigation was undertaken to evaluate the putative neuroprotective potency of LUT against neuronal damage induced by lead acetate (PbAc). Twenty-eight rats were placed into four equal groups. Group 1: served as the control group, group 2: rats were supplemented orally with LUT (50 mg kg^-1), group 3: rats were intraperitoneally injected with PbAc (20 mg kg^-1), and group 4: rats were pretreated with LUT before PbAc injection with the same doses. All animals were treated for 7 days. The exposure to PbAc increased the concentration of lead in the cortical tissue, neuronal lipid peroxidation, and nitric oxide (NO) production and decreased the antioxidant enzymes. Additionally, PbAc enhanced a neuroinflammatory response in the cortical tissue through increasing the pro-inflammatory cytokines secretion and inducible NO synthase expression. Moreover, cortical cell death was recorded following PbAc intoxication as evidenced by the enhancement of the proapoptotic and inhibiting the antiapoptotic markers. Interestingly, LUT supplementation reversed the cortical adverse reactions induced by PbAc. Taken together, these findings may suggest that LUT may be useful for attenuating neuronal damage induced by PbAc through inhibiting the oxidative damage, neuroinflammation, and the cortical cell death.

Apoptosis and astrogliosis perturbations and expression of regulatory inflammatory factors and neurotransmitters in acrylamide-induced neurotoxicity under ω3 fatty acids protection in rats

This study was aimed to investigate the potential ameliorative effects of omega-3 (ω3) fatty acids against acrylamide (ACR)-induced neurotoxicity. Thirty-two adult male Sprague Dawley rats were randomly assigned into four groups (n = 8) as follows: control, ω3 fatty acids (1000 mg/kg bwt/day orally), ACR-treated (50 mg/kg bwt/day IP) and ACR plus ω3 fatty acids group. Treatments were performed every other day for 21 consecutive days. ACR induced abnormal gait and elevated serum levels of proinflammatory cytokines (IL-6 and TNF-α), brain and spinal cord MDA levels and decreased brain and spinal cord GSH levels. Moreover, it reduced neurotransmitters (acetylcholine, GABA, serotonin and noradrenaline levels) and increased AChE activity in brain tissues. Histopathologically, ACR caused various degenerative changes, necrosis and glial cell activation in the cerebrum, cerebellum, hippocampus, spinal cord and sciatic nerve. Likewise, the histomorphometric analysis was constant with ACR-induced neurotoxicity. The ACR induced axonal atrophy and myelin disruption and decreased g-ratio of the sciatic nerve. Immunohistochemically, strong positive expressions of apoptotic marker caspase-3 and astroglial GFAP in the examined tissues were detected. Contrariwise, concurrent administration of ω3 fatty acids partially attenuated ACR impacts, as it improved the gait performance, reduced oxidative stress and pro-inflammatory cytokines, and modulate the levels of the neurotransmitters. It also ameliorated the intensity of ACR-induced histopathological and histomorphometric alterations within the examined nervous tissues. It could be concluded that ω3 fatty acids have antioxidant, anti-inflammatory and anti-apoptotic potentials against ACR neurotoxicity via suppression of oxidative stress, lipid peroxidation and pro-inflammatory cytokines, and inhibition of AChE activity and downregulation of caspase-3 and GFAP expressions in the nervous tissues.