Explained: How Covid-19 damages lungs, other organs

London, May 16:  Some cells infected with Covid-19 can "explode", leading to serious damage of the lungs and other internal organs, found a team of UK researchers including one of Indian-origin.

SARS-CoV-2 is known to cause acute respiratory distress and death in some patients. Although severe Covid is linked to substantial inflammation, how the virus triggers inflammation is not clear.

A phenomenon called a cytokine storm - when the immune system releases too many infection-fighting proteins called cytokines which then attack healthy tissue - has also long been known to cause severe damage in response to Covid infection, often leading to multiple organ failure.

However, the study, led by a team from Royal Free London (RFL), showed that immune cells infected by Covid can undergo a "cell explosion" known as pyroptosis - and causes the harmful inflammation in patients who become seriously unwell with the virus.

Although pyroptosis kills the virus, it also leads to inflammatory contents being released into the bloodstream. These inflammatory contents travel around the body, damaging the lungs and other internal organs, they said in the paper published in the journal Nature.

The new findings, however, will help researchers develop more effective treatments for stopping the process, said co-author RFL consultant hepatologist Gautam Mehta.

"The pyroptosis pathway acts as an 'alarm system'; if it senses bacterial or viral particles within the cell it leads to an 'explosion' of the cell and the release of pro-inflammatory contents. This has the benefit of eliminating the infection but can lead to severe inflammation as a result. Pyroptosis literally implies a 'fiery' mode of cell death," Mehta said.

The same process can happen in liver patients where bacteria from the gut has infected the liver. In order to expel the bacteria, the liver cells undergo the same pyroptosis process - the cells explode and release inflammatory materials that harm surrounding cells.

Mehta said in liver disease patients, this occurs because of "leaky gut", so bacterial components can reach the liver from the gut, and cause pyroptosis of liver cells leading to liver failure.

"In Covid-19, it seems this process also occurs because the virus triggers pyroptosis in immune cells, which has the benefit of eliminating the virus but can lead to hyper-inflammation in some people. It is this inflammation which can lead to acute respiratory distress and multi-organ damage," he noted.