Anti malarial drugs and g6pd deficiency

Question

Why does antimalarial drugs causes hemolysis in g6pd deficiency patients? I know that g6pd protects the cell from oxidative stress by maintaining glutathione in reduced state but how does the antimalarial drugs cause the deficiency of gsh? I came across this(https://malariaworld.org/blog/hemolytic-anemia-and-antimalarials) site and it says:

The antimalarial activity of quinine and compounds vicine and convicine present in broad beans eventually follow the same path. In the gastrointestinal tract they are hydrolyzed to form unstable pyrimidine aglycones. They reduce red blood cell GSH and generate hydrogen peroxides and free radical species.

I highly doubt the last line, how does gsh produced not prevent the cell from hemolysis?

Answer 1

Antimalarials, fever, age (of the RBC), other drugs, and a host of other things increase oxidative stress in RBCs (which results in the production of H₂O₂.)

The line you point out as a problem is a bit confusing, but it is entirely correct. It helps to keep in mind that 'glutathione' exists in two forms in the cell: glutathione disulfide (GSSG) and glutathione (GSH). GSH is the reduced form. So a reduction in GSH (the reduced form) does lead to an increase of H₂O₂.

Another way to say it is that in the absence of G6PD, the amount of reduced glutathione is decreased.

Glucose is used by RBC's as food, and G6PD is needed to metabolize it. G6PD reduces a molecule of NADP to NADPH + H⁺, which then reduces glutathione disulfide into GSH (reduced glutathione). That molecule is used in the reduction of H₂O₂ to H₂O.

If there is a deficiency of G6PH, there will not be enough NADPH to reduce GSSG, leading to decreased levels of GSH; H₂O₂ levels rise, and oxidative damage to proteins in the RBC occurs.

Glutathione metabolism consists, in large part, of its oxidation to the disulfide and recycling to the reduced form by the co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH) by mediation of glutathione reductase (Figure 1⇓). Reduced glutathione is important in the detoxification of free radicals. In normal cells, NADPH is regenerated by G6PD during oxidative stress. Impairment of this step prevents reduced glutathione recycling, exposing the cell to oxidative damage. Alternative pathways to G6PD-dependent NADPH production exist in most human cells but not in erythrocytes, and the lack of protein synthetic machinery deprives the erythrocyte of the opportunity to replace enzyme that has been lost. For these reasons, these cells are uniquely vulnerable to oxidative stress in G6PD deficiency.

These damaged proteins bind to the red cell membrane, which is then processed in the spleen; the spleen removes the damaged part of the RBC membrane. A few passes of this, and the RBC can no longer maintain the integrity of its cell membrane, and it breaks up (hemolysis).

_{Glucose-6-Phosphate Dehydrogenase Deficiency and Antimalarial Drug Development}