A study showed that Minocycline, a common antibiotic, may slow or prevent diabetic retinopathy.

Researchers, from Pennsylvania State University College of Medicine, at Hershey, found that Minocycline, often used to treat acne, limits by about 50 percent the retinal damage caused by microglia.

Microglia are cells released by the central nervous system that destroy damaged cells by surrounding them and releasing toxins.

Previous studies have shown that the changes that occur in diabetes increase the production of cytokines, proteins that cause inflammation of the nerves.
This study showed that in early diabetes elevated levels of cytokines activate microglia, which produce neurotoxins and kill nerve cells.
The neuron death causes the progressive vision loss, characteristic of diabetic retinopathy.

After establishing that microglia are activated early in the course of diabetes, investigators compared the mRNA levels of cytokines in the retinas of rats with diabetes to healthy rats.
Increasing mRNA levels are an indicator of increasing cytokine production.
The team found that there was a four- to six-fold increase in cytokines present in the retinas of diabetic rats.

Because cytokines activate microglia, the investigators asked whether the microglia in the retinas of diabetic rats were activated, and established that, indeed, they were. Then, the team treated diabetic rats with Minocycline and the mRNA levels of cytokines were subsequently measured.

" Minocycline reduces the neuroinflammation in the retina caused by cytokines, which reduces microglia activation, and hence, reduces the production of neurotoxins with less retinal nerve death, " said Steve Levison, Penn State College of Medicine. " These results confirm studies that showed that diabetes causes an early increase in the expression of inflammatory mediators within the retina, and it shows that Minocycline reduces this inflammatory component. "

To determine whether the toxins from activated microglia kill the retinal cells, the team grew active microglia with retinal cells.
Some cultures were treated with Minocycline while others were not.
Activated microglia caused a 2.5-fold increase in retinal cell death.
By contrast, in co-cultures treated with Minocycline, nearly all retinal cells survived.
An additional study in rats confirmed the results.

Source: Diabetes, 2005


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