title: Localized inhibition of P2X7R at the spinal cord injury site improves neurogenic bladder dysfunction by decreasing urothelial P2X3R expression in rats.
abstract: OBJECTIVE
  Reestablishment of bladder function in patients with spinal cord injury (SCI) is a clinical priority. Our objectives were to determine whether SCI-localized inhibition of purinergic P2X7 receptors (P2X7R) improve bladder function by decreasing afferent signals mediated by urothelial P2X3R.
  
  
  METHODS
  Systemic inhibition of P2X7R may improve locomotion in rodent SCI models; however, beneficial effects on bladder function and its physiological mechanisms have not been evaluated. We designed a thermosensitive nanohydrogel (NHG) consisting of the P2X7R antagonist brilliant blue-G (BBG) loaded into silica nanoparticles, embedded with poly(d,l-lactic-co-glycolic) acid, and resuspended in 20% pluronic acid. Female Sprague-Dawley rats with a bilateral dorsal lesion at the thoracic T8/T9 region received either 100μl of an empty NHG, or a NHG containing BBG (BBG-NHG) on top of the spinal tissue. Cystometric properties, spinal immunohistochemistry for P2X7R, and bladder immunohistochemistry for P2X3R were evaluated at four weeks post-SCI.
  
  
  RESULTS
  After SCI animals recovered hind-legs use but neurogenic bladder dysfunction remained. SCI rats treated with BBG-NHG for a period of at least two weeks post-SCI experienced fewer non-voiding contractions. The localized inhibition of P2X7R decreased microglia activation. At the lower urinary tract level we observed, unexpectedly, a concomitant reduction of urothelial P2X3 receptors, which are involved in initiation of bladder afferent transmission to start micturition.
  
  
  CONCLUSIONS
  Localized inhibition of P2X7R for two weeks can be associated with reduced number of microglia and attenuated bladder hyperexcitability mediated by downregulation of urothelial P2X3R in rats with neurogenic bladder dysfunction and independently of locomotor improvements.
authors.affiliation: Regenerative Medicine Program - Urology, Houston Methodist Research Institute, Houston, TX 77030, United States; Department of Urology, Houston Methodist Hospital, Houston, TX 77030, United States. Electronic address: AMunoz@HoustonMethodist.org.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Munoz
authors.affiliation: Regenerative Medicine Program - Nanomaterials, Houston Methodist Research Institute, Houston, TX 77030, United States.
authors.forename: Iman K
authors.initials: IK
authors.lastname: Yazdi
authors.affiliation: Department of Neurosurgery, Houston Methodist Hospital, Houston, TX 77030, United States.
authors.forename: Xiufeng
authors.initials: X
authors.lastname: Tang
authors.affiliation: Regenerative Medicine Program - Urology, Houston Methodist Research Institute, Houston, TX 77030, United States.
authors.forename: Carolina
authors.initials: C
authors.lastname: Rivera
authors.affiliation: Regenerative Medicine Program - Nanomaterials, Houston Methodist Research Institute, Houston, TX 77030, United States.
authors.forename: Nima
authors.initials: N
authors.lastname: Taghipour
authors.affiliation: Department of Neurosurgery, Houston Methodist Hospital, Houston, TX 77030, United States.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Grossman
authors.affiliation: Regenerative Medicine Program - Urology, Houston Methodist Research Institute, Houston, TX 77030, United States; Department of Urology, Houston Methodist Hospital, Houston, TX 77030, United States.
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Boone
authors.affiliation: Regenerative Medicine Program - Nanomaterials, Houston Methodist Research Institute, Houston, TX 77030, United States.
authors.forename: Ennio
authors.initials: E
authors.lastname: Tasciotti
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D005260:Female; D020100:Hydrogels; D058914:Purinergic Antagonists / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D058477:Receptors, Purinergic P2X3 / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7 / Q000187:drug effects*; D013119:Spinal Cord Injuries / Q000378:metabolism*; D001743:Urinary Bladder / Q000187:drug effects / Q000378:metabolism; D001750:Urinary Bladder, Neurogenic / Q000188:drug therapy*
chemical_list: D000199:Actins; D020100:Hydrogels; D058914:Purinergic Antagonists; D058477:Receptors, Purinergic P2X3; D058486:Receptors, Purinergic P2X7
keywords: Inflammation; Microglia; Neurogenic bladder; P2X3 purinergic receptors; P2X7 purinergic receptors; Purinergic signaling; Spinal cord injury; Urothelium