Light-Sensitive Lactococcus lactis for Microbe–Gut–Brain Axis Regulating via Upconversion Optogenetic Micro-Nano System

Abstract

The discovery of the gut–brain axis has proven that brain functions can be affected by the gut microbiota’s metabolites, so there are significant opportunities to explore new tools to regulate gut microbiota and thus work on the brain functions. Meanwhile, engineered bacteria as oral live biotherapeutic agents to regulate the host’s healthy homeostasis have attracted much attention in microbial therapy. However, whether this strategy is able to remotely regulate the host’s brain function in vivo has not been investigated. Here, we engineered three blue-light-responsive probiotics as oral live biotherapeutic agents. They are spatiotemporally delivered and controlled by the upconversion optogenetic micro–nano system. This micro–nano system promotes the small intestine targeting and production of the exogenous L. lactis in the intestines, which realizes precise manipulation of brain functions including anxiety behavior, Parkinson’s disease, and vagal afferent. The noninvasive and real-time probiotic intervention strategy makes the communiation from the gut to the host more controllable, which will enable the potential for engineered microbes accurately and effectively regulating a host’s health.

Light-regulated gene expression in Bacteria: Fundamentals, advances, and perspectives

“…Depending on wavelength, the amount of light that may be delivered per unit time can be narrowly restricted before phototoxicity sets in which may harm living cells and may obscure light-dependent signaling responses. As one workaround, upconverting nanoparticles (UNP) have been used to toggle blue-light-sensitive optogenetic circuits inside the digestive tract of animals (Yang et al, 2020;Cui et al, 2021;Pan et al, 2022). These nanoparticles are activated by NIR light (e.g., 980 nm) which penetrates biological tissue more readily and is less phototoxic than blue light.…”

“…Similarly, EL222 was used in Sinorhizobium meliloti (Pirhanov et al, 2021). Applications of none of these three optogenetic circuits are restricted to Gram-negative bacteria but extend to for instance bacilli e.g., B. subtilis (Castillo-Hair et al, 2019), and Lactococcus lactis (Pan et al, 2021;Pan et al, 2022;Zhang et al, 2021). While in most of these studies the optogenetic setups were used essentially unmodified, other reports required the optimization of plasmid backbones, promoters, ribosome-binding sites, and chromophore supply to elicit and boost light-dependent gene-expression responses (Castillo-Hair et al, 2019;Hueso-Gil et al, 2020).…”

“…Compared to constitutive expression and application of GLP-1, the optogenetically stimulated, intermittent hormone production may reduce the metabolic burden and side effects caused by GLP-1 (Zhang et al, 2021). The application of lightresponsive L. lactis proved versatile and adaptable to other ends (Pan et al, 2022). By driving the expression of the gadBC genes, encoding a glutamate decarboxylase and an antiporter, from the pDawn plasmid, the production of the neurotransmitter γaminobutyric acid (GABA) could be activated by UNPs and NIR light.…”

“…Moreover, the concentrations of several inflammatory factors in the brain were lowered upon optogenetic stimulation. The underlying strategy also applied to the light-induced production of the granulocyte-colony stimulating factor (GCSF) in L. lactis (Pan et al, 2022). In a Parkinson's disease mouse model, the light-induced GCSF production inside the gut alleviated behavioral symptoms associated with the neurological disorder.…”

Carbon Dots Derived from Os Draconis and Their Anxiolytic Effect

“…On the one hand, nanoparticles may exert neuroprotective effects by modulating the inflammatory response and reducing ROS. 44 , 45 The other nanoscale drugs were found to improve anxiety symptoms via the gut-brain axis, 46 neurotransmitters, or other pathways. 47 Research indicates that nanoparticles can enter and exit the biological barrier via exosome transfer, which is the pathway through the blood-brain barrier for many nanomedicines to exert their neurotherapeutic effects.…”