COVID-19 and demographic factors
Mitochondrial quality is relevant to COVID-19 pathology, which could
also be influenced by age and gender. Aging is proven to lead to poor
mitochondrial function, which may contribute to the suppression of
immunity and altered inflammation (Miller & Allman, 2003; Miller &
Allman, 2005; Min, Montecino-Rodriguez & Dorshkind, 2004).
Mitochondrial dysfunction induces senescence, which accumulates during
aging and contributes to inflammation that also impairs macrophages
(Franceschi et al., 2000; Wiley et al., 2016). This could contribute to
susceptibility to COVID-19 in older patients. Another relevant principle
is that mitochondrial inheritance is maternal. The mitochondria in the
egg’s cytoplasm may contain mutations harmful for females, which could
be eliminated by quality control mechanisms [114] but may not be
eliminated for males. This phenomenon may also impact mitochondrial
function and contribute to additional factors where more severe
infections could affect males. Additionally, it is claimed that the
secondary sex characteristics that men develop come at the cost of
immunity, as androgens are anti-inflammatory (Newsome, Flores, Ayala,
Gregory & Reichner, 2011; Rettew, Huet-Hudson & Marriott, 2008). Also,
in females, the X chromosome mosaicism where X chromosomes are randomly
inactivated can also influence the gender difference in viral
progression. The ACE-2 receptor encoded by the ACE-2 gene from the X
chromosome is responsible for the entry of the SARS-CoV-2 virus. Since
the gene is on the X chromosome, it may have a random distribution in
cells leading to a heterogeneous expression in females. However, males
are capable of expressing only one ACE-2 allele as every cell has the
same X chromosome. This may limit infectibility and give females a
relative resistance to the infection in comparison to males (Kloc,
Ghobrial & Kubiak, 2020). The ties between gender and immune defenses
to the mitochondria reveal a potential area of research that could lead
to the identification of effective treatment options.