Two Possible Treatments for Bipolar Disorder Found

Researchers at the University of Leeds investigating the genetic causes of bipolar disorder have identified two new drugs – one of which has already been found safe in clinical trials – that may be effective in treating the disorder.

Bipolar disorder is characterised by mood swings between mania and depression. Like autism, it is thought to be a spectrum of disorders and, although its causes are not well understood, it seems to run in families and is thought to be caused by both genetic and environmental factors.

Dr Steve Clapcote, of the Institute of Membrane and Systems Biology at the University of Leeds, who led the study, says: "We suspected from published studies of bipolar patients that levels of enzymes known as NKA or sodium pumps may be abnormal in bipolar disorder, but so far the evidence has not been convincing enough to warrant detailed clinical investigations."

The research, published today in the US journal Proceedings of the National Academy of Sciences (PNAS), used a strain of genetically modified mice that exhibit symptoms very similar to humans in the manic phase of the disorder.

The mice were bred with a particular mutation that prevents the NKA enzyme from functioning normally. When tested, the mice showed characteristics closely associated with bipolar disorder, such as increased tendency to take risks, hyperactivity, and disturbed sleep patterns. They also exhibited reduced mania when treated with anti-manic drugs.

Current drugs available to treat bipolar disorders, although usually successful, are limited to either Lithium or Valproate. They can't be matched to specific types of bipolar disorder, and can sometimes cause unpleasant side effects. There is therefore a need for treatments which can be better targeted, and which are more effective and better tolerated by patients.

The Leeds researchers found that the mice showed decreased activity of the NKA enzyme, as well as increased activity of a protein called ERK. Drugs known to have an effect on these two elements were administered to the mice, including Rostafuroxin and SL327 (see structure right), and both reduced their mania-like behaviour.

"Rostafuroxin (see structure left) has been found to be safe in clinical trials for treating high blood pressure," explained Dr Clapcote. "No one has previously looked at this drug's effects on the brain, but our mouse studies show there's a possibility that it might also be suitable for people with mania. Similarly, SL327, which is known to inhibit ERK activity, was also found to reduce manic behaviour in the mice."

"We think there is enough evidence now to start screening people with bipolar disorder to look for genetic mutations in the same NKA enzyme as that affected in our mice," says Dr Clapcote. "This will help us identify whether there is a group of bipolar patients that may be responsive to the novel treatments we have tested in the mice."....