Determinación de la actuación de los bloqueadores beta adrenérgicos sobre la vasodilatación producida por las catecolaminas en la microcirculación de tejidos cutáneos in vitro

The pathophysiology of rosacea is currently not well understood, so its treatment is nonspecific. However, recent studies have shown that there is a neurovascular dysregulation in this entity, therefore, there is a need to understand much better the molecular pathways that control permanent vasodilation of small cutaneous vessels (around 200 μm) and inflammation. In summary, the sympathetic system is the primary modulator of the cutaneous vasculature, with a multitude of identified adrenoceptors that include α1, α2, β1 and β2. Dysregulation of the sympathetic nervous system in rosacea has received considerable attention, as has modulation of alpha adrenergic receptors or beta adrenergic blockers that are helpful in some patients. Currently, recently approved therapies for the treatment of rosacea have focused on reducing erythema through vasoconstriction of the cutaneous blood vessels, targeting alpha adrenergic receptors with oxymetazoline (alpha adrenergic receptor 1 agonist, ADRA1) and with brimonidine (alpha 2 adrenergic receptor agonist, ADRA2), although its chronic use may induce typical alpha adrenergic cardiovascular disorders. For this reason, an alternative to ADRA agonists could be covered by ADRB antagonists, since they present a better safety profile and are recommended, although outside the indication card, for the treatment of erythematotelangiectatic rosacea. Although there are some reported cases of the role of ADRB antagonists in reducing rosacea associated flushing, there is currently no formal pharmacological characterization of the role of ADRB antagonists in vasoconstriction. The main objective of this thesis is to determine whether the blockade of β-adrenergic receptors would oppose vasodilation in the skin vessels. Likewise, it is intended to assess the potency of β-adrenergic antagonists (propranolol and timolol) in the vasoconstrictor response to norepinephrine and epinephrine. It is also proposed to analyze the proportion that exists between α and β adrenergic receptors in the skin vessels, which would facilitate understanding the pharmacological responses that could be obtained. For this, perfusion studies have been carried out with microcuts of human skin tissue and in arterial rings in myograph, as well as the analysis of the proportion of the expression of alpha and beta adrenergic receptors in human skin vessels by means of confocal immunofluorescence studies, quantitative PCR real-time and Western blot. The final results obtained reveal that: - Microarteries <200 μm have a lower expression of α1 adrenergic receptors and β1 adrenergic receptors, followed by α2 adrenergic receptors and with a higher expression of β2 adrenergic receptors. - The activation of α2 adrenergic receptors induced by brimonidine in microarteries smaller than 200 μm is greater than in vessels between 500-800 μm. - Contraction of vascular microcirculation induced by norepinephrine is less in vessels smaller than 200 μm than in those with a diameter between 500-800 μm. - With the blockade of α1 adrenergic receptor agonists, vasodilation induced by norepinephrine (as a β2 adrenergic receptor agonist) is greater in vessels smaller than 200 μm. - β2 adrenergic receptor antagonists such as propranolol or timolol inhibit the vasodilator effect of norepinephrine in cutaneous vessels when α1 adrenergic receptors are blocked. Therefore, our final conclusion is that the expression of β2 adrenergic receptors is predominant in microarteries <200 μm compared to other adrenoceptors, having a fundamental role in cutaneous vasodilation. These results may have a potential translational value to provide a rational blockade of β2 adrenergic receptors in the treatment of rosacea.