Early redox activities modulate Xenopus tail regeneration

Abstract

Redox state sustained by reactive oxygen species (ROS) is crucial for regeneration; however, the interplay between oxygen (O2), ROS and hypoxia-inducible factors (HIF) remains elusive. Here we observe, using an optic-based probe (optrode), an elevated and steady O2 influx immediately upon amputation. The spatiotemporal O2 influx profile correlates with the regeneration of Xenopus laevis tadpole tails. Inhibition of ROS production but not ROS scavenging decreases O2 influx. Inhibition of HIF-1α impairs regeneration and stabilization of HIF-1α induces regeneration in the refractory period. In the regeneration bud, hypoxia correlates with O2 influx, ROS production, and HIF-1α stabilization that modulate regeneration. Further analyses reveal that heat shock protein 90 is a putative downstream target of HIF-1α while electric current reversal is a de facto downstream target of HIF-1α. Collectively, the results show a mechanism for regeneration via the orchestration of O2 influx, ROS production, and HIF-1α stabilization.

Model systems for regeneration: Xenopus

“…It should be noted, however, that stabilization of a key mediator of hypoxia, hypoxia-inducible factor α (Hif1α), is not sufficient to rescue regeneration in DPI-treated tadpoles, even though Hif1α is itself necessary and sufficient for tail regeneration, via modulation of J I current reversal. This suggests that both ROS and Hif1α are independently required for regeneration (Ferreira et al, 2018).…”

“…This includes the repolarisation of cellular membrane potential (Vm) (Adams et al, 2007;Tseng et al, 2010), the transient activation of a voltage-gated sodium channel, Na V 1.2 (Tseng et al, 2010), and the reversal of electric current densities (J I ) driven by changes in trans-epithelial potential (TEP) (Ferreira et al, 2016). In addition, depletion of ROS in regeneration-competent animals using the NADPH oxidase (Nox) inhibitor DPI impairs TEP and J I dynamics, suggesting that bioelectrical signals are downstream of ROS (Ferreira et al, 2018). An indirect link between extracellular oxygen (O 2 ) influx and ROS production has also been proposed (Ferreira et al, 2018).…”

“…In addition, depletion of ROS in regeneration-competent animals using the NADPH oxidase (Nox) inhibitor DPI impairs TEP and J I dynamics, suggesting that bioelectrical signals are downstream of ROS (Ferreira et al, 2018). An indirect link between extracellular oxygen (O 2 ) influx and ROS production has also been proposed (Ferreira et al, 2018). Elevated O 2 influx correlates with closure of the wound epithelium and formation of the blastema; a similar increase is also observed following skin wounding in mice, suggesting this process is evolutionarily conserved (Ferreira et al, 2018).…”

“…An indirect link between extracellular oxygen (O 2 ) influx and ROS production has also been proposed (Ferreira et al, 2018). Elevated O 2 influx correlates with closure of the wound epithelium and formation of the blastema; a similar increase is also observed following skin wounding in mice, suggesting this process is evolutionarily conserved (Ferreira et al, 2018). This process also appears to be downstream of ROS, as DPItreated tadpoles show significant decreases in O 2 influx.…”

The vertebrate tail: a gene playground for evolution

“…Upon injury, these cells move to cover the amputation plane, where they function as an organizing center that signals to promote the proliferation of progenitors for the different tissues involved in tadpole tail regeneration [77,78]. This mobilization requires activity of reactive oxygen species (ROS), which have been shown to be produced by the wound and to play essential roles in tadpole tail regeneration [78][79][80]. Interestingly, signaling through the TGFβ pathway is an essential component of ROC signaling activity, thus connecting this regeneration process to normal tadpole tail development [45,81].…”