Zinc Overload Induces Damage to H9c2 Cardiomyocyte Through Mitochondrial Dysfunction and ROS-Mediated Mitophagy

Zinc homeostasis is essential for maintaining redox balance, cell proliferation, and apoptosis. However, excessive zinc exposure is toxic and leads to mitochondrial dysfunction. In this study, we established a zinc overload model by treating rat cardiomyocyte H9c2 cells with Zn2+ at different concentrations. Our results showed that zinc overload increased LDH and reactive oxygen species (ROS) levels, leading to cell death, mitochondrial membrane potential decrease and impaired mitochondrial function and dynamics. Furthermore, zinc overload activated the PINK1/Parkin signaling pathway and induced mitochondrial autophagy via ROS, while NAC inhibited mitophagy and weakened the activation of PINK1/Parkin pathway, thereby preserving mitochondrial biogenesis. In addition, our data also showed that Mfn2 deletion increased ROS production and exacerbated cytotoxicity induced by zinc overload. Our results therefore suggest that Zn2+-induced ROS generation causes mitochondrial autophagy and mitochondrial dysfunction, damaging H9c2 cardiomyocytes. Additionally, Mfn2 may play a key role in zinc ion-mediated endoplasmic reticulum and mitochondrial interactions. Our results provide a new perspective on zinc-induced toxicology.

[Cervical myelopathy due to copper deficiency secondary to dental zinc overload: A case report]

We present the case of a 68-year-old man with progressive brachial and crural hypoaesthesia with gait ataxia suggesting subacute myelopathy of the posterior cords, demonstrated by MRI. After blood tests, a diagnosis of copper deficiency was made following zinc intoxication, secondary to the use of denture glue containing zinc. Treatment was started with copper and the dental glue was removed. Rehabilitation treatment was started with physiotherapy, hydrotherapy and occupational therapy. Functional improvement was achieved, going from an ASIAD level C4 to an ASIAD level C7 spinal cord injury. Copper levels should be studied in all non-compressive myelopathies of subacute onset if there is clear involvement of the posterior cords. Copper deficiency in analysis would establish the diagnosis. Rehabilitative treatment, supplementary copper supplementation and zinc withdrawal are essential to prevent irreversible neurological damage.