Cadmium Impairs Autophagy Leading to Apoptosis by Ca2+-Dependent Activation of JNK Signaling Pathway in Neuronal Cells

From Fundamentals to Innovation in Alzheimer's Disease: Molecular Findings and Revolutionary Therapies

Alzheimer's disease (AD) is a global health concern and the leading cause of dementia in the elderly. The prevalence of this neurodegenerative condition is projected to increase concomitantly with increased life expectancy, resulting in a significant economic burden. With very few FDA-approved disease-modifying drugs available for AD, there is an urgent need to develop new compounds capable of impeding the progression of the disease. Given the unclear etiopathogenesis of AD, this review emphasizes the underlying mechanisms of this condition. It explores not only well-studied aspects, such as the accumulation of Aβ plaques and neurofibrillary tangles, but also novel areas, including glymphatic and lymphatic pathways, microbiota and the gut-brain axis, serotoninergic and autophagy alterations, vascular dysfunction, the metal hypothesis, the olfactory pathway, and oral health. Furthermore, the potential molecular targets arising from all these mechanisms have been reviewed, along with novel promising approaches such as nanoparticle-based therapy, neural stem cell transplantation, vaccines, and CRISPR-Cas9-mediated genome editing techniques. Taking into account the overlap of these various mechanisms, individual and combination therapies emerge as the future direction in the AD strategy.

Angelica sinensis polysaccharides mitigate cadmium-induced apoptosis in layer chicken chondrocytes by inhibiting the JNK signaling pathway

Cadmium (Cd), a toxic heavy metal pollutant, inflicts widespread damage on various organs and tissues, including cartilage, where it induces chondrocyte apoptosis. Angelica sinensis polysaccharides (ASP), a key active component of the traditional Chinese medicine Angelica sinensis, have been shown to possess anti-apoptotic effects on chondrocytes. This study investigates the in vitro effects of ASP on alleviating Cd-induced apoptosis in layer chicken chondrocytes, focusing on the mitochondrial apoptosis pathway mediated by the c-Jun N-terminal kinase (JNK) signaling pathway. Chondrocytes were isolated from layer chicken embryos and confirmed to express collagen type II alpha 1 (Col2a1). We found that Cd triggered apoptosis in the chondrocytes; however, the use of the JNK inhibitor SP 600125 mitigated mitochondrial structural damage casused by Cd, indicating the involvement of JNK signaling in this process. Furthermore, ASP effectively alleviated Cd-induced apoptosis in layer chicken chondrocytes by inhibiting JNK signaling in vitro. Our findings provide a theoretical foundation for the clinical application of ASP in preventing Cd-induced cartilage diseases in poultry.

Metal Toxicity and Dementia Including Frontotemporal Dementia: Current State of Knowledge

Frontotemporal dementia (FTD) includes a number of neurodegenerative diseases, often with early onset (before 65 years old), characterized by progressive, irreversible deficits in behavioral, linguistic, and executive functions, which are often difficult to diagnose due to their similar phenotypic characteristics to other dementias and psychiatric disorders. The genetic contribution is of utmost importance, although environmental risk factors also play a role in its pathophysiology. In fact, some metals are known to produce free radicals, which, accumulating in the brain over time, can induce oxidative stress, inflammation, and protein misfolding, all of these being key features of FTD and similar conditions. Therefore, the present review aims to summarize the current evidence about the environmental contribution to FTD-mainly dealing with toxic metal exposure-since the identification of such potential environmental risk factors can lead to its early diagnosis and the promotion of policies and interventions. This would allow us, by reducing exposure to these pollutants, to potentially affect society at large in a positive manner, decreasing the burden of FTD and similar conditions on affected individuals and society overall. Future perspectives, including the application of Artificial Intelligence principles to the field, with related evidence found so far, are also introduced.

Heavy Metal Mediated Progressive Degeneration and Its Noxious Effects on Brain Microenvironment

Heavy metals, including lead (Pb), cadmium (Cd), arsenic (As), cobalt (Co), copper (Cu), manganese (Mn), zinc (Zn), and others, have a significant impact on the development and progression of neurodegenerative diseases in the human brain. This comprehensive review aims to consolidate the recent research on the harmful effects of different metals on specific brain cells such as neurons, microglia, astrocytes, and oligodendrocytes. Understanding the potential influence of these metals in neurodegeneration is crucial for effectively combating the ongoing advancement of these diseases. Metal-induced neurodegeneration involves molecular mechanisms such as apoptosis induction, dysregulation of metabolic and signaling pathways, metal imbalance, oxidative stress, loss of synaptic transmission, pathogenic peptide aggregation, and neuroinflammation. This review provides valuable insights by compiling the supportive evidence from recent research findings. Additionally, we briefly discuss the modes of action of natural neuroprotective compounds. While this comprehensive review aims to consolidate the recent research on the harmful effects of various metals on specific brain cells, it may not cover all studies and findings related to metal-induced neurodegeneration. Studies that are done using bioinformatics tools, microRNAs, long non-coding RNAs, emerging disease models, and studies based on the modes of exposure to toxic metals are a future prospect to be explored.

From inflammation to pyroptosis: Understanding the consequences of cadmium exposure in chicken liver cells

Hepatotoxicity is frequently observed following acute cadmium (Cd) exposure in chicken. Oxidative stress and subsequent inflammation are regarded as the main reasons for cadmium-induced liver injury. NOD-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome-induced pyroptosis is involved in various inflammatory diseases, including liver injury. Poultry are more susceptible to harmful effects of heavy metals. However, the mechanism of cadmium-induced liver injury in chicken is still elusive. In this study, the effect of cadmium on chicken liver cells and the underlying mechanisms were investigated. The results showed mitochondria was damaged and excessive reactive oxygen species (ROS) were generated in chicken liver cell line LMH after cadmium exposure. Furthermore, cadmium-induced NLRP3 inflammasome activation and the cell membrane rupture indicated LMH cells pyroptosis. The ROS scavengers, acetylcysteine (NAC) and Mito-TEMPO prevented pyroptosis in LMH cells, suggesting that ROS were responsible for the activation of the NLRP3 inflammasome induced by cadmium. Additionally, anti-oxidative transcription factor Nrf2 was inhibited after cadmium exposure, explaining the excessive ROS generation. In summary, our study showed that cadmium leads to ROS generation by inducing mitochondrial damage and inhibiting Nrf2 activity, which promotes NLRP3 inflammasome activation and eventually induces pyroptosis in LMH cells.

Mechanisms of Cadmium Neurotoxicity

Cadmium is a heavy metal that increasingly contaminates food and drink products. Once ingested, cadmium exerts toxic effects that pose a significant threat to human health. The nervous system is particularly vulnerable to prolonged, low-dose cadmium exposure. This review article provides an overview of cadmium's primary mechanisms of neurotoxicity. Cadmium gains entry into the nervous system via zinc and calcium transporters, altering the homeostasis for these metal ions. Once within the nervous system, cadmium disrupts mitochondrial respiration by decreasing ATP synthesis and increasing the production of reactive oxygen species. Cadmium also impairs normal neurotransmission by increasing neurotransmitter release asynchronicity and disrupting neurotransmitter signaling proteins. Cadmium furthermore impairs the blood-brain barrier and alters the regulation of glycogen metabolism. Together, these mechanisms represent multiple sites of biochemical perturbation that result in cumulative nervous system damage which can increase the risk for neurological and neurodegenerative disorders. Understanding the way by which cadmium exerts its effects is critical for developing effective treatment and prevention strategies against cadmium-induced neurotoxic insult.

Targeting Autophagy, Apoptosis, and Oxidative Perturbations with Dapagliflozin Mitigates Cadmium-Induced Cognitive Dysfunction in Rats

Cognitive decline and Alzheimer-like neuropathology are common manifestations of cadmium toxicity. Thanks to its antioxidant/anti-apoptotic features, dapagliflozin has demonstrated promising neuroprotective actions. However, its effect on cadmium-induced neurotoxicity is lacking. The present work aimed to examine whether dapagliflozin could protect rats from cadmium-evoked cognitive decline. In this study, the behavioral disturbances and hippocampal biomolecular alterations were studied after receiving dapagliflozin. Herein, cadmium-induced memory/learning decline was rescued in the Morris water maze, novel object recognition task, and Y-shaped maze by dapagliflozin. Meanwhile, the hippocampal histopathological abnormalities were mitigated. The molecular mechanisms revealed that dapagliflozin lowered hippocampal expression of p-tau and Aβ42 neurotoxic proteins while augmenting acetylcholine. The cognitive enhancement was triggered by hippocampal autophagy stimulation, as indicated by decreased SQSTM-1/p62 and Beclin 1 upregulation. Meanwhile, a decrease in p-mTOR/total mTOR and an increase in p-AMPK/total AMPK ratio were observed in response to dapagliflozin, reflecting AMPK/mTOR cascade stimulation. Dapagliflozin, on the other hand, dampened the pro-apoptotic processes in the hippocampus by downregulating Bax, upregulating Bcl-2, and inactivating GSK-3β. The hippocampal oxidative insult was mitigated by dapagliflozin as seen by lipid peroxide lowering, antioxidants augmentation, and SIRT1/Nrf2/HO-1 pathway activation. In conclusion, dapagliflozin's promising neuroprotection was triggered by its pro-autophagic, anti-apoptotic, and antioxidant properties.

Cadmium induces apoptosis of mouse spermatocytes through JNK activation and disruption of autophagic flux

Cadmium has been reported to accumulate primarily in spermatogonia and spermatocytes. Exposure to cadmium results in male reproductive toxicity via germ-cell apoptosis and impaired autophagy. Apoptosis and autophagy are two physiologically conserved events that maintain cellular homeostasis. However, the precise role of autophagy in cadmium-induced apoptosis of male germ cells has yet to be addressed. The present study aimed to investigate the impact of cadmium exposure on the cytotoxicity of GC-2 spd cells, a mouse spermatocyte cell line. The results showed that cadmium exposure caused apoptotic cell death and the accumulation of autophagosomes, along with the up-regulation of ATG proteins in GC-2 spd cells. It was demonstrated that the cadmium-induced accumulation of autophagosomes contributes to the apoptosis of GC-2 spd cells. This notion is supported by the findings that the autophagy inhibitor 3-MA reduced accumulation of autophagosomes and apoptotic cell death. Conversely, the apoptosis inhibitor Z-VAD-FMK inhibited apoptosis but had little effect on the accumulation of autophagosomes. Cadmium may impede the fusion of autophagosomes with lysosomes, leading to the autophagosome buildup. Additionally, we found that the JNK pathway mediates transcriptional induction of several autophagy-related (ATG) genes involved in autophagosome formation. The cadmium-activated JNK pathway regulates apoptosis by mediating the autophagosome formation. Treatment of cells with the JNK inhibitor SP600125 attenuated the accumulation of autophagosomes, the upregulated expression of autophagosome-associated proteins and apoptotic cell death induced by cadmium. Overall, these findings suggest that cadmium enhances apoptosis of GC-2 spd cells by activating the JNK pathway and inhibiting autophagic flux.

Targeting Autophagy, Apoptosis, and SIRT1/Nrf2 Axis with Topiramate Underlies Its Neuroprotective Effect against Cadmium-Evoked Cognitive Deficits in Rats

Cadmium is an environmental toxicant that instigates cognitive deficits with excessive glutamate excitatory neuroactivity in the brain. Topiramate, a glutamate receptor antagonist, has displayed favorable neuroprotection against epilepsy, cerebral ischemia, and Huntington's disease; however, its effect on cadmium neurotoxicity remains to be investigated. In this study, topiramate was tested for its potential to combat the cognitive deficits induced by cadmium in rats with an emphasis on hippocampal oxidative insult, apoptosis, and autophagy. After topiramate intake (50 mg/kg/day; p.o.) for 8 weeks, behavioral disturbances and molecular changes in the hippocampal area were explored. Herein, Morris water maze, Y-maze, and novel object recognition test revealed that topiramate rescued cadmium-induced memory/learning deficits. Moreover, topiramate significantly lowered hippocampal histopathological damage scores. Mechanistically, topiramate significantly replenished hippocampal GLP-1 and dampened Aβ42 and p-tau neurotoxic cues. Notably, it significantly diminished hippocampal glutamate content and enhanced acetylcholine and GABA neurotransmitters. The behavioral recovery was prompted by hippocampal suppression of the pro-oxidant events with notable activation of SIRT1/Nrf2/HO-1 axis. Moreover, topiramate inactivated GSK-3β and dampened the hippocampal apoptotic changes. In tandem, stimulation of hippocampal pro-autophagy events, including Beclin 1 upregulation, was triggered by topiramate that also activated AMPK/mTOR pathway. Together, the pro-autophagic, antioxidant, and anti-apoptotic features of topiramate contributed to its neuroprotective properties in rats intoxicated with cadmium. Therefore, it may be useful to mitigate cadmium-induced cognitive deficits.

Neuroprotective Impact of Linagliptin against Cadmium-Induced Cognitive Impairment and Neuropathological Aberrations: Targeting SIRT1/Nrf2 Axis, Apoptosis, and Autophagy

Cadmium is an environmental contaminant associated with marked neurotoxicity and cognitive impairment. Linagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, has demonstrated promising neuroprotection against cerebral ischemia and diabetic dementia. However, there has been no study of its effect on cadmium-induced cognitive deficits. In the present work, linagliptin's prospective neuroprotective effects against cadmium-evoked cognitive decline were examined in vivo in rats. The molecular pathways related to oxidative stress, apoptosis, and autophagy were investigated. Histology, immunohistochemistry, ELISA, and biochemical assays were performed on brain hippocampi after receiving linagliptin (5 mg/kg/day). The current findings revealed that cadmium-induced learning and memory impairment were improved by linagliptin as seen in the Morris water maze, Y-maze, and novel object recognition test. Moreover, linagliptin lowered hippocampal neurodegeneration as seen in histopathology. At the molecular level, linagliptin curtailed hippocampal DPP-4 and augmented GLP-1 levels, triggering dampening of the hippocampal neurotoxic signals Aβ42 and p-tau in rats. Meanwhile, it enhanced hippocampal acetylcholine and GABA and diminished the glutamate spike. The behavioral recovery was associated with dampening of the hippocampal pro-oxidant response alongside SIRT1/Nrf2/HO-1 axis stimulation. Meanwhile, linagliptin counteracted hippocampal apoptosis markers and inhibited the pro-apoptotic kinase GSK-3β. In tandem, linagliptin activated hippocampal autophagy by lowering SQSTM-1/p62 accumulation, upregulating Beclin 1, and stimulating AMPK/mTOR pathway. In conclusion, linagliptin's antioxidant, antiapoptotic, and pro-autophagic properties advocated its promising neuroprotective impact. Thus, linagliptin may serve as a management approach against cadmium-induced cognitive deficits.

Activation of Endothelial Large Conductance Potassium Channels Protects against TNF-α-Induced Inflammation

Elevated TNF-α levels in serum and broncho-alveolar lavage fluid of acute lung injury patients correlate with mortality rates. We hypothesized that pharmacological plasma membrane potential (Em) hyperpolarization protects against TNF-α-induced CCL-2 and IL-6 secretion from human pulmonary endothelial cells through inhibition of inflammatory Ca2+-dependent MAPK pathways. Since the role of Ca2+ influx in TNF-α-mediated inflammation remains poorly understood, we explored the role of L-type voltage-gated Ca2+ (CaV) channels in TNF-α-induced CCL-2 and IL-6 secretion from human pulmonary endothelial cells. The CaV channel blocker, Nifedipine, decreased both CCL-2 and IL-6 secretion, suggesting that a fraction of CaV channels is open at the significantly depolarized resting Em of human microvascular pulmonary endothelial cells (-6 ± 1.9 mV), as shown by whole-cell patch-clamp measurements. To further explore the role of CaV channels in cytokine secretion, we demonstrated that the beneficial effects of Nifedipine could also be achieved by Em hyperpolarization via the pharmacological activation of large conductance K+ (BK) channels with NS1619, which elicited a similar decrease in CCL-2 but not IL-6 secretion. Using functional gene enrichment analysis tools, we predicted and validated that known Ca2+-dependent kinases, JNK-1/2 and p38, are the most likely pathways to mediate the decrease in CCL-2 secretion.

The Effect of Oxidative Stress-Induced Autophagy by Cadmium Exposure in Kidney, Liver, and Bone Damage, and Neurotoxicity

Environmental and occupational exposure to cadmium has been shown to induce kidney damage, liver injury, neurodegenerative disease, and osteoporosis. However, the mechanism by which cadmium induces autophagy in these diseases remains unclear. Studies have shown that cadmium is an effective inducer of oxidative stress, DNA damage, ER stress, and autophagy, which are thought to be adaptive stress responses that allow cells exposed to cadmium to survive in an adverse environment. However, excessive stress will cause tissue damage by inducing apoptosis, pyroptosis, and ferroptosis. Evidently, oxidative stress-induced autophagy plays different roles in low- or high-dose cadmium exposure-induced cell damage, either causing apoptosis, pyroptosis, and ferroptosis or inducing cell survival. Meanwhile, different cell types have different sensitivities to cadmium, which ultimately determines the fate of the cell. In this review, we provided a detailed survey of the current literature on autophagy in cadmium-induced tissue damage. A better understanding of the complex regulation of cell death by autophagy might contribute to the development of novel preventive and therapeutic strategies to treat acute and chronic cadmium toxicity.

The crosstalk among autophagy, apoptosis, and pyroptosis in cardiovascular disease

In recent years, the mechanism of cell death has become a hotspot in research on the pathogenesis and treatment of cardiovascular disease (CVD). Different cell death modes, including autophagy, apoptosis, and pyroptosis, are mosaic with each other and collaboratively regulate the process of CVD. This review summarizes the interaction and crosstalk of key pathways or proteins which play a critical role in the entire process of CVD and explores the specific mechanisms. Furthermore, this paper assesses the interrelationships among these three cell deaths and reviews how they regulate the pathogenesis of CVD. By understanding how these three cell death modes go together we can learn about the pathogenesis of CVD, which will enable us to identify new targets for preventing, controlling, and treating CVD. It will not only reduce mortality but also improve the quality of life.

Baicalin induces apoptosis and autophagy in human osteosarcoma cells by increasing ROS to inhibit PI3K/Akt/mTOR, ERK1/2 and β-catenin signaling pathways

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Baicalin causes apoptosis and autophagy through accumulating ROS to suppress PI3K/Akt/mTOR, ERK1/2 and β-catenin pathways in OS cells.

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Baicalin-induced autophagosome further triggers apoptosis.

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Baicalin-induced ROS and Ca²⁺ interactions induce apoptosis.

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Baicalin molecule targets PI3Kγ, inhibiting downstream effectors AKT and mTOR.

Baicalin, a flavonoid derivative, exerts antitumor activity in a variety of neoplasms. However, whether baicalin exerts antitumor effects on osteosarcoma cells remains to be elucidated. In this study, treatment with baicalin reduced the proliferation and invasive potential of osteosarcoma cells and reduced the mitochondrial membrane potential, which eventually caused mitochondrial apoptosis. In addition, baicalin increased intercellular Ca²⁺ and ROS concentrations. Baicalin-induced apoptosis was confirmed by enhanced Bax, cleaved caspase-3, and cleaved PARP levels and decreased Bcl-2 levels. The increase in LC3-II and p62 suggested that baicalin induced autophagosome formation but ultimately inhibited downstream autophagy. Moreover, apoptosis induced by baicalin was attenuated by the addition of 3-MA. Furthermore, we found that baicalin inhibited the PI3K/Akt/mTOR, ERK1/2 and β-catenin signaling pathways. Chelation of free Ca²⁺ by BAPTA-AM also inhibited both apoptosis induction and ROS concentration changes. Finally, NAC pretreatment reversed baicalin treatment outcomes, including the increase in Ca²⁺ concentration, induction of apoptosis and autophagy, and inhibition of the pathways. Molecular docking results indicated that baicalin might interact with the structural domain of PI3Kγ. Thus, baicalin may be considered a potential candidate for osteosarcoma treatment.