COVID-19 outbreak, stress, atherosclerosis and immune function
Stress is a major factor that can alter the immune system. During the
lockdown due to the pandemic, a huge number of persons have developed
relevant signs of psychological suffering, that can significantly affect
the capacity of the organism to react to external stimuli like those
represented by microorganisms. It has been known for a long time that
the immune response is regulated by soluble factors which include not
only numerous cytokines and chemokines, but also a large number of
hormones and neurotransmitters, whose receptors are found both on cells
of innate and acquired immunity. Among these molecules, glucocorticoids
play a fundamental role, and are responsible for a variety of
immunological effects. Psychological stress, as well as several
proinflammatory cytokines, acts at the hypothalamus level, provoking the
production and release of corticotropin-releasing hormone (CRH) and
arginine vasopressin (AVP) that, in turn, induce the anterior pituitary
gland to synthesize adrenocorticotropin hormone (ACTH), which is able to
stimulate steroidogenesis in adrenocortical cells. 5,6This is crucial to give origin to cortisol, the main corticosteroid. In
turn, glucocorticoids trigger a negative feedback, according to which
the hypothalamic–pituitary–adrenal axis is inhibited. In general, it
can be well stated that the main physiological effects of
glucocorticoids go in the direction to suppress immune responses.
However, these are not the only important effects described for these
molecules. Atherosclerosis is a process in which ACTH and cortisol may
play an important role. Acting on proinflammatory or anti-inflammatory
cytokines, they can regulate vascular endothelial functionality and
recruit monocytes, that can enter the wall and differentiate first into
macrophages, second into foam cells. Their capability to modulate the
capacity of macrophages to remove the excess free cholesterol from the
atherosclerotic plaque is also crucial for maintaining an efficient
endothelial functionality. 6 The pathogenesis of
COVID-19 is associated with elevation of several immune plays as well as
inflammatory factors which contributes to cytokine storms.