Does deteriorating antioxidant defense and impaired γ-glutamyl cycle induce oxidative stress and hemolysis in individuals with sickle cell disease?

Sickle cell disease (SCD) affects two-thirds of African and Indian children. Understanding the molecular mechanisms contributing to oxidative stress may be useful for therapeutic development in SCD. We evaluated plasma elemental levels of Indian SCD patients, trait and healthy controls (n=10/per group) via ICP-MS. Additionally, erythrocyte metabolomics of Indian SCD and healthy (n=5/per group) was carried out using LC-MS mass-spectrometry. Followed by assessment of antioxidant defence enzymes namely glutathione reductase (GR), superoxide dismutase (SOD), and catalase (CAT) in erythrocytes and plasma of Indian SCD patients (n=31) compared to trait (n=8) and healthy (n=9). In SCD plasma an elevated plasma 24Mg, 44Ca, 66Zn, 208Pb, 39K and reduced 57Fe, 77Se, 85Rb levels indicating higher hemolysis and anemia. Erythrocyte metabolome of SCD patients clustered separately from heathy revealing 135 significantly deregulated metabolic features including trimethyllysine, pyroglutamate, glutathione, aminolevulinate, and D-glutamine indicating oxidative stress and membrane fragility. Repressed GR, SOD, and CAT activities were observed in SCD patients of which GR and CAT activities did not change under hypoxia. These findings lead to the hypothesis that SCD-associated metabolic deregulations and a shift to ATP-consuming aberrant γ-glutamyl cycle leads to anemia, dehydration, oxidative stress and hemolysis driving the biomechanical pathophysiology of erythrocyte of SCD patients.

Zinc2+ ion inhibits SARS-CoV-2 main protease and viral replication in vitro.

Zinc deficiency is linked to poor prognosis in COVID-19 patients while clinical trials with zinc demonstrate better clinical outcomes. The molecular targets and mechanistic details of the anti-coronaviral activity of zinc remain obscure. We show that zinc not only inhibits the SARS-CoV-2 main protease (Mpro) with nanomolar affinity, but also viral replication. We present the first crystal structure of the Mpro-Zn2+ complex at 1.9 Å and provide the structural basis of viral replication inhibition. We show that Zn2+ coordinates with the catalytic dyad at the enzyme active site along with two previously unknown water molecules in a tetrahedral geometry to form a stable inhibited Mpro-Zn2+ complex. Further, the natural ionophore quercetin increases the anti-viral potency of Zn2+. As the catalytic dyad is highly conserved across SARS-CoV, MERS-CoV and all variants of SARS-CoV-2, Zn2+ mediated inhibition of Mpro may have wider implications.