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 O₂influx immediately upon amputation. The spatiotemporal O₂influx profile correlates with the regeneration ofXenopus laevistadpole tails. Inhibition of ROS production but not ROS scavenging decreases O₂influx. Inhibition of HIF-1α impairs regeneration and stabilization of HIF-1α induces regeneration in the refractory period. In the regeneration bud, hypoxia correlates with O₂influx, 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 O₂influx, ROS production, and HIF-1α stabilization.

Reactive oxygen species (ROS) and electric currents modulate regeneration; however, the interplay between biochemical and biophysical signals during regeneration remains poorly understood. We investigate the interactions between redox and bioelectric activities during tail regeneration in Xenopus laevis tadpoles. We show that inhibition of NADPH oxidase-mediated production of ROS, or scavenging or blocking their diffusion into cells, impairs regeneration and consistently regulates the dynamics of membrane potential, transepithelial potential (TEP) and electric current densities (JI) during regeneration. Depletion of ROS mimics the altered TEP and JI observed in the non-regenerative refractory period. Short-term application of hydrogen peroxide (H2O2) rescues (from depleted ROS) and induces (from the refractory period) regeneration, TEP increase and JI reversal. H2O2 is therefore necessary for and sufficient to induce regeneration and to regulate TEP and JI. Epistasis assays show that voltage-gated Na+ channels act downstream of H2O2 to modulate regeneration. Altogether, these results suggest a novel mechanism for regeneration via redox-bioelectric orchestration.

Many bacterial pathogens hijack macrophages to egress from the port of entry to the lymphatic drainage and/or bloodstream, causing dissemination of life-threatening infections. However, the underlying mechanisms are not well understood. Here, we report that Salmonella infection generates directional electric fields (EFs) in the follicle-associated epithelium of mouse cecum. In vitro application of an EF, mimicking the infection-generated electric field (IGEF), induces directional migration of primary mouse macrophages to the anode, which is reversed to the cathode upon Salmonella infection. This infection-dependent directional switch is independent of the Salmonella pathogenicity island 1 (SPI-1) type III secretion system. The switch is accompanied by a reduction of sialic acids on glycosylated surface components during phagocytosis of bacteria, which is absent in macrophages challenged by microspheres. Moreover, enzymatic cleavage of terminally exposed sialic acids reduces macrophage surface negativity and severely impairs directional migration of macrophages in response to an EF. Based on these findings, we propose that macrophages are attracted to the site of infection by a combination of chemotaxis and galvanotaxis; after phagocytosis of bacteria, surface electrical properties of the macrophage change, and galvanotaxis directs the cells away from the site of infection. Bacterial pathogens can invade and survive within macrophages and use them as a vehicle to reach important organs of a human body, resulting in life-threatening infections, but the underlying mechanisms are not well understood. Our current understanding is that macrophages are recruited to the infected site by sensing gradients of chemokines and/or cytokines released by damaged cells—a process known as chemotaxis. However, this mechanism does not explain how macrophages containing the pathogens escape the site to reach the bloodstream. Here, we use a disseminated Salmonella infection model in mice and detect electric fields (EFs) generated by Salmonella infection at the gut epithelium, which can drive unidirectional migration of macrophages towards the anode—a biological process also known as galvanotaxis. We further demonstrate that macrophage galvanotaxis can be reversed to the cathode by phagocytosis of the bacteria. Based on these findings, we propose that macrophages are attracted to the site of infection by a combination of chemotaxis and galvanotaxis; after phagocytosis of bacteria, the electrical properties of the macrophage change, and galvanotaxis directs the cells away from the site of infection allowing the escape of the macrophages that contain pathogens.

Directed collective cell migration is essential for morphogenesis, and chemical, electrical, mechanical and topological features have been shown to guide cell migration in vitro. Here we provide in vivo evidence showing that endogenous electric fields drive the directed collective cell migration of an embryonic stem cell population—the cephalic neural crest of Xenopus laevis. We demonstrate that the voltage-sensitive phosphatase 1 is a key component of the molecular mechanism, enabling neural crest cells to specifically transduce electric fields into a directional cue in vivo. Finally, we propose that endogenous electric fields are mechanically established by the convergent extension movements of the ectoderm, which generate a membrane tension gradient that opens stretch-activated ion channels. Overall, these findings establish a role for electrotaxis in tissue morphogenesis, highlighting the functions of endogenous bioelectrical stimuli in non-neural contexts.

Wounds naturally produce electric signals which serve as powerful cues that stimulate and guide cell migration during wound healing. In diabetic patients, impaired wound healing is one of the most challenging complications in diabetes management. A fundamental gap in knowledge is whether diabetic wounds have abnormal electric signaling. Here we used a vibrating probe to demonstrate that diabetic corneas produced significantly weaker wound electric signals than the normal cornea. This was confirmed in three independent animal models of diabetes: db/db, streptozotocin-induced and mice fed a high-fat diet. Spatial measurements illustrated that diabetic cornea wound currents at the wound edge but not wound center were significantly weaker than normal. Time lapse measurements revealed that the electric currents at diabetic corneas lost the normal rising and plateau phases. The abnormal electric signals correlated significantly with impaired wound healing. Immunostaining suggested lower expression of chloride channel 2 and cystic fibrosis transmembrane regulator in diabetic corneal epithelium. Acute high glucose exposure significantly (albeit moderately) reduced electrotaxis of human corneal epithelial cells in vitro, but did not affect the electric currents at cornea wounds. These data suggest that weaker wound electric signals and impaired electrotaxis may contribute to the impaired wound healing in diabetes.