Japanese researchers have found that abnormal delivery of zinc to lung cells contributes to obstructive pulmonary diseases, a collective term for refractory respiratory diseases with chronic airway inflammation and excessive mucus retention that are accompanied by airway obstruction.

The findings, published in the journal EbioMedicine, also suggest that treatment for these diseases cannot be performed merely with zinc supplements. 

The study by researchers at Kumamoto University in Japan showed that there could be abnormality in the zinc transport mechanism itself in obstructive pulmonary diseases. 

A therapeutic approach that takes the zinc transport mechanisms into consideration is, therefore, necessary, according to the research.

Obstructive pulmonary diseases include chronic obstructive pulmonary disease (COPD) that presents with chronic bronchitis or pulmonary emphysema, and cystic fibrosis (CF), an intractable hereditary disease characterised by mucus retention and chronic bacterial infection.

A main cause of COPD is cigarette smoke. The onset and progression of the disease is caused by transporter proteins that allow ions to permeate ion channels into cells. 

COPD is thought to involve the overactivation of the epithelial sodium ion (Na+) channel (ENaC). 

Cystic fibrosis, on the other hand, is a genetic disease that is caused by genetic mutation of a chloride ion (Cl-) channel called the cystic fibrosis transmembrane conductance regulator (CFTR).

Excessive production of mucus-producing genes in the lungs has been known for some time to be important in the development of diseases such as COPD and CF. 

However, it was not clear why excessive production of these mucus genes occurs in these pulmonary diseases, particularly since they have such different causes, such as tobacco and heredity.

Examining cell lines from patients, this new study made it clear that abnormalities of the ion channels EnaC and CFTR reduce the body's ability to deliver zinc ions to lung epithelial cells, which is linked to overproduction of mucous genes.

The study showed that diseases developed due to an overproduction of mucus was, in turn, caused by an insufficient zinc supply to lung epithelial cells.