title: Systemic TAK-242 prevents intrathecal LPS evoked hyperalgesia in male, but not female mice and prevents delayed allodynia following intraplantar formalin in both male and female mice: The role of TLR4 in the evolution of a persistent pain state.
abstract: Pain resulting from local tissue injury or inflammation typically resolves with time. Frequently, however, this pain may unexpectedly persist, becoming a pathological chronic state. Increasingly, the innate and adaptive immune systems are being implicated in the initiation and maintenance of these persistent conditions. In particular, Toll-like receptor 4 (TLR4) signaling has been shown to mediate the transition to a persistent pain state in a sex-dependent manner. In the present work, we explored this contribution using the TLR4 antagonist, TAK-242.
  
  
  
  Male and female C57Bl/6 mice were given intravenous (IV), intrathecal (IT), or intraperitoneal (IP) TAK-242 prior to IT delivery of lipopolysaccharide (LPS), and tactile reactivity was assessed at regular intervals over 72-h. Additional groups of mice were treated with IP TAK-242 prior to intraplantar formalin, and flinching was monitored for 1-h. Tactile reactivity was assessed at 7-days after formalin delivery.
  
  
  
  LPS evoked TNF release from male and female macrophages and RAW267.4 cells, which was blocked in a concentration dependent fashion by TAK-242. In vivo, IT LPS evoked tactile allodynia to a greater degree in male than female mice. TAK-242, given by all routes, prevented development of IT LPS-induced tactile allodynia in male animals, but did not reverse their established allodynia. TLR4 deficiency and TAK-242 treatment attenuated IT LPS-induced allodynia in male, but not female mice. In the formalin model, pre-treatment with TAK-242 did not affect Phase 1 or Phase 2 flinching, but prevented the delayed tactile allodynia in both male and unexpectedly in female mice (Phase 3).
  
  
  
  Together, these results suggest that TAK-242 is a TLR4 antagonist that has efficacy after systemic and intrathecal delivery and confirms the role of endogenous TLR4 signaling in triggering the development of a delayed allodynia in both male and female mice.
authors.affiliation: Department of Anesthesiology, University of California San Diego, La Jolla, CA, USA; Department of Medicine, Division of Rheumatology, Allergy, and Immunology, University of California San Diego, La Jolla, CA, USA. Electronic address: swoller@ucsd.edu.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Woller
authors.affiliation: Epigen Biosciences Inc., 10225 Barnes Canyon Road, Suite A104, San Diego, CA 92121, USA. Electronic address: sravula@epigenbiosciences.com.
authors.forename: Satheesh B
authors.initials: SB
authors.lastname: Ravula
authors.affiliation: Epigen Biosciences Inc., 10225 Barnes Canyon Road, Suite A104, San Diego, CA 92121, USA. Electronic address: ftucci@epigenbiosciences.com.
authors.forename: Fabio C
authors.initials: FC
authors.lastname: Tucci
authors.affiliation: Epigen Biosciences Inc., 10225 Barnes Canyon Road, Suite A104, San Diego, CA 92121, USA. Electronic address: gbeaton@epigenbiosciences.com.
authors.forename: Graham
authors.initials: G
authors.lastname: Beaton
authors.affiliation: Department of Medicine, Division of Rheumatology, Allergy, and Immunology, University of California San Diego, La Jolla, CA, USA. Electronic address: mpcorr@ucsd.edu.
authors.forename: Maripat
authors.initials: M
authors.lastname: Corr
authors.affiliation: Department of Dermatology, School of Medicine, University of California, Davis, CA, USA. Electronic address: rrisseroff@ucdavis.edu.
authors.forename: R Rivkah
authors.initials: RR
authors.lastname: Isseroff
authors.affiliation: Department of Dermatology, School of Medicine, University of California, Davis, CA, USA; Shriners Hospital for Children, Northern California, Sacramento, CA, USA. Electronic address: asoulika@ucdavis.edu.
authors.forename: Athena M
authors.initials: AM
authors.lastname: Soulika
authors.affiliation: Department of Dermatology, School of Medicine, University of California, Davis, CA, USA. Electronic address: mchigbrow@ucdavis.edu.
authors.forename: Marianne
authors.initials: M
authors.lastname: Chigbrow
authors.affiliation: Department of Anesthesiology, University of California San Diego, La Jolla, CA, USA. Electronic address: keddinger@ucsd.edu.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Eddinger
authors.affiliation: Department of Anesthesiology, University of California San Diego, La Jolla, CA, USA. Electronic address: tyaksh@ucsd.edu.
authors.forename: Tony L
authors.initials: TL
authors.lastname: Yaksh
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D059350:Chronic Pain / Q000139:chemically induced / Q000517:prevention & control*; D004195:Disease Models, Animal; D004202:Disinfectants / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D005557:Formaldehyde / Q000008:administration & dosage / Q000494:pharmacology; D006930:Hyperalgesia / Q000139:chemically induced / Q000517:prevention & control*; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D000067996:RAW 264.7 Cells; D012737:Sex Factors; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013449:Sulfonamides / Q000008:administration & dosage / Q000494:pharmacology*; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors* / Q000172:deficiency; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects*
chemical_list: D004202:Disinfectants; D008070:Lipopolysaccharides; D013449:Sulfonamides; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C507035:ethyl 6-(N-(2-chloro-4-fluorophenyl)sulfamoyl)cyclohex-1-ene-1-carboxylate; D005557:Formaldehyde
keywords: Formalin; LPS; Mouse; TAK-242; TLR4; TNF; Tactile allodynia