E-NTPDases in human airways: Regulation and relevance for chronic lung diseases

Abstract

Chronic obstructive lung diseases are characterized by the inability to prevent bacterial infection and a gradual loss of lung function caused by recurrent inflammatory responses. In the past decade, numerous studies have demonstrated the importance of nucleotide-mediated bacterial clearance. Their interaction with P2 receptors on airway epithelia provides a rapid Fon-and-off_ signal stimulating mucus secretion, cilia beating activity and surface hydration. On the other hand, abnormally high ATP levels resulting from damaged epithelia and bacterial lysis may cause lung edema and exacerbate inflammatory responses. Airway ATP concentrations are regulated by ecto nucleoside triphosphate diphosphohydrolases (E-NTPDases) which are expressed on the mucosal surface and catalyze the sequential dephosphorylation of nucleoside triphosphates to nucleoside monophosphates (ATP Y ADP Y AMP). The common bacterial product, Pseudomonas aeruginosa lipopolysaccharide (LPS), induces an acute reduction in azide-sensitive ENTPDase activities, followed by a sustained increase in activity as well as NTPDase 1 and NTPDase 3 expression. Accordingly, chronic lung diseases, including cystic fibrosis (CF) and primary ciliary dyskinesia, are characterized by higher rates of nucleotide elimination, azide-sensitive E-NTPDase activities and expression. This review integrates the biphasic regulation of airway E-NTPDases with the function of purine signaling in lung diseases. During acute insults, a transient reduction in E-NTPDase activities may be beneficial to stimulate ATP-mediated bacterial clearance. In chronic lung diseases, elevating E-NTPDase activities may represent an attempt to prevent P2 receptor desensitization and nucleotide-mediated lung damage.

Cystic fibrosis remodels the regulation of purinergic signaling by NTPDase1 (CD39) and NTPDase3

“…Total RNA was extracted from cultured and freshly excised human airway epithelial cells (9). Reverse transcriptase (RT) reactions were conducted with the Superscript III First Strand kit (Invitrogen, Carlsbad, CA), and specific antisense primers for NTPDase1 (5=-TGTGGACAATGGTTGCTCAGC-3=), NTPDase3 (5=-CAAGAGACCAGGCTATGCTGCTAT-3=), and internal standard ␤-actin (Ambion, Austin, TX), as we previously described (8). The cDNA was amplified using the Platinum PCR Supermix (Invitrogen) and specific primers for NTPDase1 (sense, 5=-AAGAGATTTGAGAT-GACTCTTCCATTC-3=; antisense, 5=-AGCCTTGCAGAAGGAGG-GAGA-3=), NTPDase3 (sense, 5=-TGGCAGGAG AGAAGATGGATC-3=; antisense, 5=-AAGTGGTAGAGTTAGTTGGCTGAGAAG-3=), and ␤-actin (Ambion).…”

“…For instance, NTPDase1 is considered a low-capacity, high-affinity ectonucleotidase [K m ϭ 10 -20 M (11)], whereas NTPDase3 falls in the high-capacity, low-affinity category regulating higher nucleotide concentrations [K m ϭ 90 -130 M (72)]. We recently reported a strong sensitivity of nucleotide metabolism to azide on HBE cultures (Ͼ40%) (8), supporting a major role for NTPDase1 (42) and/or NTPDase3 (72), but not the other surface NTPDases (26,71), NSAP (30), or NPPs (69). Human NTPDase1 has been extensively investigated and assigned critical roles in the prevention of ischemia-reperfusion injury (31) and transplant rejection (2,67), in thrombus formation, and inflammatory responses (6,20).…”

Overexpression of CD39 in Mouse Airways Promotes Bacteria-Induced Inflammation

“…At present, eight human P2Y receptors-P2Y 1 , P2Y 2 , P2Y 4 , P2Y 6 , P2Y [11][12][13][14] -and seven P2X subtypes-P2X 1-7 -have been identified. P2 receptor-mediated signals are quickly terminated due to receptor desensitization and/ or scavenging of ATP by cell-surface ecto-nucleotidases.…”

“…P2 receptor-mediated signals are quickly terminated due to receptor desensitization and/ or scavenging of ATP by cell-surface ecto-nucleotidases. In airways, ATP is converted into adenosine through a two-step enzymatic process mediated by the ecto-nucleoside triphosphate diphosphohydrolase CD39 (conversion of ATP and ADP to AMP) and the ecto-59-nucleotidase CD73 (conversion of AMP to adenosine) that play major roles in the regulation of physiological mucosal nucleotide concentrations (6). Adenosine activates P1 receptors identified as A 1 , A 2A , A 2B , and A 3 receptors (5).…”

“…Particularly, chronic lung disease is characterized by higher rates of nucleotide elimination, ecto-nucleoside triphosphate diphosphohydrolase expression, and activity (6). Transgenic mice that lack CD39 develop increased pulmonary edema and inflammation compared with control littermates in a model of acute lung injury (17).…”