Punctate Administration of Ficin as a human and animal model of non-histaminergic itch.

BACKGROUND: Ficin, a cysteine protease derived from fig-tree latex, has been reported to elicit itch and nociceptive sensations, though quantitative sensory studies are lacking. Cowhage containing the pruritic cysteine Mucunain, on the contrary, has been widely studied as activating polymodal nociceptors and eliciting a histamine-independent itch. OBJECTIVES: We tested whether ficin in heat-inactivated cowhage spicules would elicit itch and nociceptive sensations in humans, and analogous behaviours in mice, which are similar to those evoked by native cowhage, and whether these behaviours in mice were dose-dependent when ficin was injected intradermally. METHODS: Human volunteers rated the magnitude of itch and nociceptive sensations evoked by either native cowhage spicules or heat-inactivated spicules soaked in 1, 10 or 100 mg/mL ficin (0.03, 0.3 and 3 ng of ficin in spicule tip), applied to forearm. In mice, itch-like scratching and nociceptive-like wiping were recorded in response to either native cowhage, to heat-inactivated spicules that were either inactive or contained 100 mg/mL ficin, or to intradermal injections of 1.25, 2.5 or 5 µg/ 5 µL, each treatment applied to the cheek. RESULTS: The dose of 100 mg/mL ficin in spicules evoked comparable magnitudes of itch, nociceptive sensations and areas of cutaneous dysesthesia as native cowhage in humans and comparable itch-like scratching and pain-like wiping behaviours in mice. But to elicit similar behaviours when injected intradermally in mice a greater amount of ficin (1.25 µg) was required. CONCLUSION: Spicule delivery or intradermal injection of ficin elicits behaviours in mice that model itch and nociceptive sensations in humans, suggesting that ficin may be useful in translating mechanistic research on the neural mechanisms of pruritic and nociceptive effects of cysteine proteases between the two species.

Activating Akt1 mutations alter DNA double strand break repair and radiosensitivity.

The survival kinase Akt has clinical relevance to radioresistance. However, its contributions to the DNA damage response, DNA double strand break (DSB) repair and apoptosis remain poorly defined and often contradictory. We used a genetic approach to explore the consequences of genetic alterations of Akt1 for the cellular radiation response. While two activation-associated mutants with prominent nuclear access, the phospho-mimicking Akt1-TDSD and the clinically relevant PH-domain mutation Akt1-E17K, accelerated DSB repair and improved survival of irradiated Tramp-C1 murine prostate cancer cells and Akt1-knockout murine embryonic fibroblasts in vitro, the classical constitutively active membrane-targeted myrAkt1 mutant had the opposite effects. Interestingly, DNA-PKcs directly phosphorylated Akt1 at S473 in an in vitro kinase assay but not vice-versa. Pharmacological inhibition of DNA-PKcs or Akt restored radiosensitivity in tumour cells expressing Akt1-E17K or Akt1-TDSD. In conclusion, Akt1-mediated radioresistance depends on its activation state and nuclear localization and is accessible to pharmacologic inhibition.