ABSTRACT
Heme oxygenase-1 (HO-1) is a cytoprotective enzyme that catalyzes the conversion of heme to CO, biliverdin, and iron, which together protect cells from oxidative and inflammatory damage and play an important role in maintaining cell homeostasis. In recent years, HO-1 has also been found to have antiviral biological effects, and the induced expression of HO-1 inhibits the replication of various viruses such as hepatitis C virus, hepatitis B virus, human immunodeficiency virus, dengue virus, ebolavirus, influenza A virus, Zika virus, severe acute respiratory syndrome coronavirus 2, human respiratory syncytial virus, hepatitis A virus and enterovirus 71. The inhibitory effect of HO-1 on these viruses involves three mechanisms, including direct inhibition of virus replication by HO-1 and its downstream products, enhancement of type I interferon responses in host cell, and attenuation of inflammatory damage caused by viral infection. This review focuses on the recent advances in the antiviral effect of HO-1 and its mechanism, which is expected to provide evidence for HO-1 as a potential target for antiviral therapy.
ABSTRACT
The SARS-CoV-2 spike has been regarded as the main target of antibody design against COVID-19. Two single-site mutations, R190K and N121Q, were deemed to weaken the binding affinity of biliverdin although the underlying molecular mechanism is still unknown. Meanwhile, the effect of the two mutations on the conformational changes of "lip" and "gate" loops was also elusive. Thus, molecular dynamics simulation and molecular mechanics/generalized Born surface area (MM/GBSA) free energy calculation were conducted on the wild-type and two other SARS-CoV-2 spike mutants. Our simulations indicated that the R190K mutation causes Lys190 to form six hydrogen bonds, guided by Asn99 and Ile101, which brings Lys190 closer to Arg102 and Asn121, thereby weakening the interaction energy between biliverdin and Ile101 as well as Lys190. For the N121Q mutation, Gln121 still maintained a hydrogen bond with biliverdin; nevertheless, the overall binding mode deviated significantly under the reversal of the side chain of Phe175. Moreover, the two mutants would stabilize the lip loop, which would restrain the meaningful upward movement of the lip. In addition, N121Q significantly promoted the gate loop deviating to the biliverdin binding site and compressed the site. This work would be useful in understanding the dynamics binding biliverdin to the SARS-CoV-2 spike.
ABSTRACT
Bilirubin has been proven to possess significant anti-inflammatory, antioxidant and antiviral activities. Recently, it has been postulated as a metabolic hormone. Further, moderately higher levels of bilirubin are positively associated with reduced risk of cardiovascular diseases, diabetes, metabolic syndrome and obesity. However, due to poor solubility the therapeutic delivery of bilirubin remains a challenge. Nanotechnology offers unique advantages which may be exploited for improved delivery of bilirubin to the target organ with reduced risk of systemic toxicity. Herein, we postulate the use of intravenous administration or inhalational delivery of bilirubin nanomedicine (BNM) to combat systemic dysfunctions associated with COVID-19, owing to the remarkable preclinical efficacy and optimistic results of various clinical studies of bilirubin in non-communicable disorders. BNM may be used to harness the proven preclinical pharmacological efficacy of bilirubin against COVID-19 related systemic complications.