Adenosine Promotes Wound Healing and Mediates Angiogenesis in Response to Tissue Injury Via Occupancy of A2A Receptors

Collagen and matrix deposition by fibroblasts is an essential part of wound healing but also contributes to pathologic remodeling of organs leading to substantial morbidity and mortality. Adenosine, a small molecule generated extracellularly from adenine nucleotides as a result of direct stimulation, hypoxia, or injury, acts via a family of classical sevenpass G protein-coupled protein receptors, A 2A and A 2B , leading to generation of cAMP and activation of downstream targets such as PKA and Epac. These effectors, in turn, lead to fibroblast activation and collagen synthesis. The regulatory actions of these receptors likely involve multiple interconnected pathways, and one of the more interesting aspects of this regulation is opposing effects at different levels of cAMP generated. Additionally, adenosine signaling contributes to fibrosis in organ-specific ways and may have opposite effects in different organs. The development of drugs that selectively target these receptors and their signaling pathways will disrupt the pathogenesis of fibrosis and slow or arrest the progression of the important diseases they underlie.

Section: The Role Of Adenosine and Its Receptors In Granulation Tissumentioning

confidence: 99%

Section: The Role Of Adenosine and Its Receptors In Granulation Tissumentioning

confidence: 99%

Section: The Role Of Adenosine and Its Receptors In Granulation Tissumentioning

confidence: 99%

See 1 more Smart Citation

Signaling pathways involving adenosine A2A and A2B receptors in wound healing and fibrosis

Shaikh

Cronstein

2016

“…In fact, adenosine is a potent anti-inflammatory agent with A 2A Rs triggering BOFF^signals in activated immune cells, which constitutes one of the most fundamental and immediate tissue-protecting mechanisms (reviewed in [295,296]). A 2A R agonists were even named Bthe most potent anti-inflammatory drug known to mankind.^Ac-cordingly, activation of A 2A Rs has been shown to confer a robust protection against tissue damage from ischemiaYreperfusion injury in different organ such as heart [297Y299], blood vessels [300], kidney [301,302], liver [303,304], lung [305,306], joints [307], skin [308,309], and even in the spinal cord [310,311] and in the brain following hemorrhage [312] or acute infection [313]. Thus, it is the activation (rather the blockade) of A 2A Rs that confers protection against damage triggered by inflammation in peripheral tissues, precisely the opposite of what is observed in the damaged adult brain.…”

Section: A 2a Receptor Blockade Confers Robust Neuroprotectionmentioning

confidence: 99%

Neuroprotection by adenosine in the brain: From A1 receptor activation to A2A receptor blockade

Cunha

2005

470

428

Adenosine is a neuromodulator that operates via the most abundant inhibitory adenosine A 1 receptors (A 1 Rs) and the less abundant, but widespread, facilitatory A 2A Rs. It is commonly assumed that A 1 Rs play a key role in neuroprotection since they decrease glutamate release and hyperpolarize neurons. In fact, A 1 R activation at the onset of neuronal injury attenuates brain damage, whereas its blockade exacerbates damage in adult animals. However, there is a down-regulation of central A 1 Rs in chronic noxious situations. In contrast, A 2A Rs are up-regulated in noxious brain conditions and their blockade confers robust brain neuroprotection in adult animals. The brain neuroprotective effect of A 2A R antagonists is maintained in chronic noxious brain conditions without observable peripheral effects, thus justifying the interest of A 2A R antagonists as novel protective agents in neurodegenerative diseases such as Parkinson's and Alzheimer's disease, ischemic brain damage and epilepsy. The greater interest of A 2A R blockade compared to A 1 R activation does not mean that A 1 R activation is irrelevant for a neuroprotective strategy. In fact, it is proposed that coupling A 2A R antagonists with strategies aimed at bursting the levels of extracellular adenosine (by inhibiting adenosine kinase) to activate A 1 Rs might constitute the more robust brain neuroprotective strategy based on the adenosine neuromodulatory system. This strategy should be useful in adult animals and especially in the elderly (where brain pathologies are prevalent) but is not valid for fetus or newborns where the impact of adenosine receptors on brain damage is different.Abbreviations: Ab -b-amyloid peptide; A 1 Rs -A 1 receptors; A 2A Rs -A 2A

“…In addition, adenosine also stimulates cell migration, proliferation, and angiogenesis [129,130]. Experimental evidence suggests that adenosine evokes wound closure via A 2A receptor activation, since A 2A agonists promote early wound closure while A 2A antagonists impede the healing process [131]. The continuous denudation and repair of airway epithelium occurs especially in inflammatory airways diseases such as asthma [132].…”

Section: Pulmonary Epithelium Injurymentioning

confidence: 99%

Perspectives of purinergic signaling in stem cell differentiation and tissue regeneration

Glaser

Cappellari

Pillat

et al. 2011

Replacement of lost or dysfunctional tissues by stem cells has recently raised many investigations on therapeutic applications. Purinergic signaling has been shown to regulate proliferation, differentiation, cell death, and successful engraftment of stem cells originated from diverse origins. Adenosine triphosphate release occurs in a controlled way by exocytosis, transporters, and lysosomes or in large amounts from damaged cells, which is then subsequently degraded into adenosine. Paracrine and autocrine mechanisms induced by immune responses present critical factors for the success of stem cell therapy. While P1 receptors generally exert beneficial effects including anti-inflammatory activity, P2 receptor-mediated actions depend on the subtype of stimulated receptors and localization of tissue repair. Pro-inflammatory actions and excitatory tissue damages mainly result from P2X7 receptor activation, while other purinergic receptor subtypes participate in proliferation and differentiation, thereby providing adequate niches for stem cell engraftment and novel mechanisms for cell therapy and endogenous tissue repair. Therapeutic applications based on regulation of purinergic signaling are foreseen for kidney and heart muscle regeneration, Clara-like cell replacement for pulmonary and bronchial epithelial cells as well as for induction of neurogenesis in case of neurodegenerative diseases.