CBD could reduce lung damage from COVID-19
Cannabidiol (CBD) appears to reduce the cytokine storm that damages the lungs and kills many patients with the novel coronavirus (COVID-19) by enabling an increase in levels of a natural peptide called apelin, which is known to reduce inflammation, according to a new study by the Medical College of Georgia at Augusta University published in the Journal of Cellular and Molecular Medicine.
The researchers previously reported in the journal Cannabis and Cannabinoid Research that treatment with CBD reduced excessive lung inflammation, enabling improvements in lung function, heathier oxygen levels, and repair of some of the structural damage to the lungs that are classic with acute respiratory distress syndrome (ARDS).
In the current study, the researchers correlated those improvements with regulation of apelin. While they don't attribute all of CBD's benefits to apelin, they said the peptide has an important role. They also don't yet know whether COVID-19, or CBD for that matter, have a direct effect on apelin, or if these are downstream consequences.
For the studies, a control group received intranasal saline for three consecutive days while the COVID-19 model received POLY (I:C) intranasally for three days. A third group, the treatment group, received POLY ((I:C) and CBD over the same timeframe.
With the current study, the researchers found significantly reduced apelin levels in the mice that developed COVID-like symptoms compared to controls. Treatment with CBD normalized the immune response and apelin levels, along with oxygen levels and swelling and scarring in the lungs, according to the study.
Blood levels of the peptide apelin dropped close to zero in the study model and increased 20 times with CBD, the researchers said. Apelin is a pervasive peptide made by cells in the heart, lung, brain, fat tissue and blood, and is an important regulator in bringing both blood pressure and inflammation down. When blood pressure gets high, apelin levels help bring it down. Apelin should do the same to help normalize the significant increases in inflammation in the lungs and related breathing difficulties associated with ARDS, the researchers said.
The COVID-19 virus enters human cells via the also pervasive angiotensin-converting enzyme 2 (ACE2) receptor. Apelin and ACE2 also normally work together to control blood pressure, and upregulation of both may be helpful in cardiovascular disease, including heart failure, by decreasing blood pressure while increasing the heart's ability to pump. Apelin and ACE2 work together to regulate a healthy cardiovascular system and they are factors in many conditions, like obesity or hypertension, that hurt the cardiovascular system, the researchers said.
As seen with other diseases, COVID-19 appears to upset this positive partnership. The virus' binding to the receptor for ACE2 has been shown to decrease ACE2 levels and increase levels of the powerful blood vessel constrictor angiotensin II, because less angiotensin II gets degraded and fewer vasodilators get produced, which worsens the patient's prognosis, the researchers said.
While the researchers said they are still putting the pieces together, reduced levels of ACE2 appear to enable less apelin and less protection. The researchers said the finding of dramatic reductions in apelin in the face of ARDS, makes levels of the protective peptide a potential early biomarker for ARDS and response to treatment efforts.