MEDICAL FRONTIER

Has cancer found its bane in Vitamin C?

Washington: US researchers have found that giving Vitamin C intravenously can produce super-high concentration in the blood, which has ability to attack cancer cells. The findings, published recently in the journal Redox Biology, revealed that vitamin C breaks down easily, generating hydrogen peroxide, a so-called reactive oxygen species that can damage tissue and DNA, says ANI.

Researchers from University of Iowa Health Care in the US also showed that tumour cells are much less capable of removing the damaging hydrogen peroxide than normal cells. They also found that giving vitamin C intravenously -and bypassing normal gut metabolism and excretion pathways- creates blood levels that are 100-500 times higher than levels seen with oral ingestion.

“In this paper we demonstrate that cancer cells are much less efficient in removing hydrogen peroxide than normal cells. Thus, cancer cells are much more prone to damage and death from a high amount of hydrogen peroxide,” said Garry Buettner.

“This explains how the very, very high levels of vitamin C used in our clinical trials do not affect normal tissue, but can be damaging to tumour tissue,” Buettner added. They examined how high-dose vitamin C (also known as ascorbate) kills cancer cells.

The team tested the approach in clinical trials for pancreatic cancer and lung cancer that combine high-dose, intravenous vitamin C with standard chemotherapy or radiation. The new study shows that an enzyme called catalase is the central route for removing hydrogen peroxide generated by decomposing vitamin C.

The researchers discovered that cells with lower amounts of catalase activity were more susceptible to damage and death when they were exposed to high amounts of vitamin C. “Our results suggest that cancers with low levels of catalase are likely to be the most responsive to high-dose vitamin C therapy, whereas cancers with relatively high levels of catalase may be the least responsive,” he explained.

Blindness cure: Fish eyes hold the key!

Washington: Scientists, including one of Indian origin, have identified a chemical signal in the zebra fish brain that helps it regenerate retina, a finding that may help cure blindness in humans.

The discovery raises the possibility that human retinas can be induced to regenerate, naturally repairing damage caused by degenerative retinal diseases and injury, including age-related macular degeneration and retinitis pigmentosa, researchers said. “The prevailing belief has been that the regeneration process in fish retinas is triggered by secreted growth factors, but our results indicate that the neurotransmitter GABA might initiate the process instead,” said James Patton, Professor at Vanderbilt University in the US.

“All the regeneration models assume that a retina must be seriously damaged before regeneration takes place, but our studies indicate that GABA can induce this process even in undamaged retinas,” said Patton.

It turns out the structure of retinas of fish and mammals are basically the same. Although the retina is very thin, less than 0.5 mm thick, it contains three layers of nerve cells: photoreceptors that detect the light, horizontal cells that integrate the signals from the photoreceptors and ganglion cells that receive the visual information and route it to the brain. In addition, the retina contains a special type of adult stem cell called Muller glia that span all three layers and provide mechanical support and electrical insulation. In fish retinas, they also play a key role in regeneration.

When regeneration is triggered, the Muller glia dedifferentiate, begin proliferating, and then differentiate into replacements for the damaged nerve cells. Muller glia are also present in mammalian retinas, but do not regenerate.

Graduate student Mahesh Rao got the idea that GABA (normally a fast-acting neurotransmitter best known for its role of calming nervous activity by inhibiting nerve transmission in the brain) might be the trigger for retinal regeneration.

He was inspired by the results of a study in the mouse hippocampus which found that GABA was controlling stem cell activity.