As of today, there isn’t anyone who would not be familiar with COVID-19, which is short for Coronavirus 2019. Having wreaked havoc over the past 8 months worldwide, the virus is notorious for lung infection and inflammation. Caused by SARS-CoV-2 (Severe Acute Respiratory Syndrome Corona Virus 2), the search for a vaccine continues.
The most common symptoms of COVID-19 are fever, dry cough, and tiredness, whereas less common symptoms are aches, sore throat, diarrhoea, etc. Serious symptoms of this disease are dyspnoea (shortness of breath/difficulty in breathing), increased chest pressure, and/or loss of speech/movement.
On a molecular basis, inflammation and infection accompany each other in COVID-19. While the infection is the invasion and replication/multiplication of a disease-causing pathogen in the body, inflammation is the response shown by the body to 1) fight off the symptoms caused by the pathogens, 2) restore the body to normal.
Inflammation itself consists of elimination of the initial cause of cell injury, removal of necrotic/dead cells, and initiation of tissue repair. An inflammatory reaction can be harmful to a person if it is excessive, prolonged, or inappropriate.
Let us have a look at the cardinal signs of inflammation:
Redness and warmth: which are because of increased blood flow in the vessels, due to chemical mediators of inflammation: histamine, prostaglandins, bradykinin, Nitric Oxide (NO).
Swelling: due to endothelial contraction/disruption which raises the pressure in the affected area. This is regulated by leukotrienes (C4, D4, E4), histamine, and serotonin.
Pain in inflammation is due to the sensitization of sensory nerve endings, caused by bradykinin, prostaglandin E2, and histamine.
The loss of function of the inflamed area due to the above-mentioned factors is a hallmark of inflammation.
What are cytokines?
Cytokines are a huge category of proteins, which are important in cell signalling pathways (a lot of small proteins and messengers are involved in carrying out the work inside the cell, and from one entity to another, the signalling is important). Under the broad category of cytokines fall, chemokines, interferons (IFN), interleukins (IL-), lymphokines (from lymphocytes, a type of white blood cell, a guardian of the body), and tumour necrosis factors (TNF), and growth factors (GF).
All these cytokines have different roles in the human body, and they work according to their capacity. Abnormal or no function of these can lead to messing up the bodily function.
Stringing this back to COVID-19, excessive inflammation and cytokine storm have been seen in patients with this rampant disease.
The cytokine storm is responsible for causing extreme inflammation, which then adds up to cough, fever, and muscular pain. Extreme cases of the cytokine storm and inflammation result in pneumonia and obstructed lungs, leading to breathing difficulties. One effective way, therefore, is to reduce the inflammation caused by cytokine storm, and in turn, tone down inflammation. This can be done specifically by giving drugs that lessen interleukin-6 (IL-6) amounts in the body. The aforementioned savior drug Actemra or tocilizumab targets IL-6 and clears the clogged-up lungs of patients, giving a brilliant recovery rate of almost 90%. However, it also causes hypertriglyceridemia (a condition where triglyceride fat deposition increases in the blood, the accumulation of which can lead to heart disease), and pancreatitis, the inflammation of the pancreas. The need to have a less harsh viral therapy for COVID-19 is still pressing.
Other proinflammatory, or inflammation-promoting cytokines include IL-1α, IL-1β, TNF-α, and IL-17A. Apart from these, there are also macrophage inflammatory protein-1α (MIP-1α), interferon-gamma inducible protein-10 (IFNγ-IP-10), also known as CXCL10, monocyte chemoattractant protein-1 (MCP-1), interleukin-II (IL-2), and tumour necrosis factor-α (TNF-α). All these pro-inflammatory entities have shown to have a contribution to the pathology of severe cases of COVID-19. A successful remedy is sought to reduce these inflammation-promoting cytokines, and promotes and increases the production of interferons (IFNs), signalling proteins which activate different types of white blood cells in the body and stop viruses from multiplying.
During the whole COVID-19 ordeal, the uncertainties in terms of financial insecurities, destruction of the economy, and isolation cause anxiety and depression in the general public. Learning more about COVID-19 and its treatment and prevention might help the patients too because an increased number of cytokines in the body leads to an increase in anxiety.