An Itchy Situation

November 2, 2013 by

Nov. 1, 2013

By Medical Discovery News

Anyone ever bitten by a mosquito can attest to its itchy consequences. New research has discovered just how our bodies detect and process itching, leading to a better understanding of our reaction to itching and hopefully better treatments for it.

The clinical term for an itch is pruritus, and at least 16 percent of people experience an itch that just doesn’t go away. The most common dermatological complaint, long-term itching can be caused by chronic renal disease, cirrhosis, some cancers, multiple sclerosis, diabetes, shingles, allergic reactions, drug reactions, and pregnancy.

Prolonged itching and scratching can increase the intensity of the itch, possibly leading to neurodermatitis, a condition in which a frequently scratched area of skin becomes thick and leathery. The patches can be raw, red, or darker than the rest of the skin. Persistent scratching can also lead to a bacterial skin infection, permanent scars, or changes in skin color. The super strong pain reliever morphine can cause such a severe whole-body itch that some patients choose to forgo it and live with the pain.

Sensory neurons called TRPV1 cells detect itchy substances on skin. TRPV1 cells have long nerve fibers that extend into skin, muscle, and other tissues to help monitor conditions. It has not been clear how these neurons sort through different sensations like pain and temperature and route the signal along the proper pathway to the appropriate area of the brain for perception.

New research has revealed a small group of those neurons produce a substance called natriuretic polypeptide b (Nppb), a hormone known to be involved in regulating the heart. Surprisingly, when Nppb is produced by TRPV1 cells it acts as a neurotransmitter, a chemical messenger secreted by neurons to carry, boost, and control signals between neurons and other cells.

When scientists genetically modified mice to eliminate Nppb, they did not itch. Nppb binds to a specific receptor called Npra on particular nerves in the spinal column. When those cells were eliminated in mice, again, they did not itch. Interestingly, removing these cells did not impact other sensory sensations such as temperature, pain, and touch.

A similar transmission presumably exists in humans, but that has not yet been determined. Knowing which molecules and cells are involved will help scientists study how humans perceive itch signals. Before these findings, scientists thought a molecule called gastrin releasing peptide was responsible for transmitting the itch signal from nerves, and that itching was a low level form of pain.

Understanding the itch signaling pathway offers the opportunity to create drugs that specifically block that signal and alleviate unpleasant and chronic itching with fewer side effects.

For a link to this story, click here.

Filed Under: Health Tagged With: , , , , , , , , , , , , , , , ,

New Hope for MS

February 22, 2013 by

Feb. 22, 2013

By Medical Discovery News

Pictures from the 2012 presidential campaign depict Ann Romney, wife of Republican candidate Mitt Romney, as a woman with bright eyes, a luminous smile, and a dancer’s posture. But beneath the polished business suit of a potential first lady another battle raged.

Ann Romney was diagnosed with multiple sclerosis (MS) many years ago and experienced a flare up of her symptoms that forced her to curtail her campaign efforts. There is no known cause or cure for MS, although medications are available to slow the progression of the disease. However, researchers at the National Institutes of Health discovered the drug daclizumab appears to tone down the autoimmune response in MS patients, providing hope for those like Ann Romney who are trying to overcome the obstacles of living with MS.

MS is a type of autoimmune disorder, meaning cells in the body’s own immune system that are supposed to provide protection from invading infections instead attack the body’s own healthy tissues. In the case of MS, the immune system attacks the myelin sheath that covers nerve cells. Myelin is crucial in the conduction of electrical impulses to and from the brain. The loss of myelin, called demyelination, causes hardened scars in areas of the nerves and brain affected. The name multiple sclerosis actually means “many scars.” MS is the most common disease of the central nervous system in young adults, affecting 400,000 Americans. 

In the NIH study, researchers identified a unique type of immune cell called lymphoid tissue inducer (LTi) cells, which promote the development of lymph nodes and similar tissues in a fetus. While it is unclear what LTi cells do in adults, they appear to play a role in the immunity in the gastrointestinal tract. This study implicates these cells may contribute to MS, although they have not previously been linked to any autoimmune disorder.

MS patients in the study receiving daclizumab had reduced levels of LTi cells and reduced signs of inflammation in the cerebrospinal fluid, which surrounds the brain and spinal column, when compared to a control group that didn’t receive the drug. This drug is an engineered antibody that interferes with the signals produced by a molecule called interleukin 2 (IL-2) that promotes inflammation. Antibodies are specialized proteins made by the immune system that target and bind to antigens, in this case the IL-2 protein, to eliminate or block their actions.

By blocking IL-2 action, it seems like daclizumab reduces inflammation and the damage that happens in MS. More studies will have to confirm the role of LTi cells in MS before the development of drugs to selectively target LTi cells can begin in earnest. But one day, such drugs may become part of the treatment for MS and hopefully slow the progression of this disease more effectively. 

For a link to this story, click here.

Filed Under: Uncategorized Tagged With: , , , , , , ,