Partial secretome analysis of Caldariomyces fumago reveals extracellular production of the CPO co-substrate H2O2 and provides a coproduction concept for CPO and glucose oxidase

Iron-Based Nanoplatforms Achieve Hepatocellular Carcinoma Regression Through a Cascade of Effects

Purpose

Ferroptosis is a regulated form of cell death characterized by iron-dependent accumulation of associated lipid peroxides (LPO), which can induce cell death when a certain level is reached. However, the extremely complex tumor microenvironment (TME) has the characteristics of antioxidant, even if it induces ferroptosis of tumor cells, its killing effect on tumor cells is still very limited. To solve this problem, we constructed a novel nanomaterials (GOx/EC@Fe3O4@CCM). We evaluated the anticancer effect of this nanomaterial in inhibiting tumor growth through comprehensive in vitro and in vivo experiments.

Methods

We successfully synthesized GOx/EC@Fe3O4 by one-pan synthesis method, then coated the Hepatocellular carcinoma cell membrane on its surface by co-extrusion technology, and finally synthesized the GOx/EC@Fe3O4@CCM nanoplatforms. We characterized the compounds in terms of morphology, particle size, and Zeta potential. In addition, we also studied the anti-tumor effect of GOx/EC@Fe3O4@CCM nanoplatforms from the following aspects, including the performance test of the nanoplatform, the intracellular effect of the nanoplatform, the anti-tumor effect in vitro, the intracellular ROS analysis, the intracellular effect of EC, and the anti-tumor effect in vivo.

Results

The iron-based carriers in GOx/EC@Fe3O4@CCM nanoplatforms are released and produce ferrous ions (Fe2+) in an acidic environment. Due to the limitation of the endogenous level of hydrogen peroxide (H2O2), we introduced GOx into the TME or tumor cells. Under the catalysis of GOx, glucose reacted rapidly to produce a large amount of H2O2, which then combined with Fe2+ to produce a large number of Hydroxyl radical (·OH). Its toxicity leads to dysfunction of cell membrane and organelles, and then causes cell damage. EC inhibits Nuclear factor erythroid 2-related factor 2 (Nrf2) in cancer cells, which effectively down-regulates downstream gene products, including NAD(P)H quinone oxidoreductase 1 (NQO1) and heme oxygenase 1 (HMOX1). A series of chain reactions reduce the escape effect of oxidative stress (OS) and effectively maintain a high level of intracellular oxidation. Furthermore, it induces sustained and intense ferroptosis in tumor cells. Finally, the use of cancer cell membrane modified nanoplatforms due to the homology of membrane protein components improves the tumor cell targeting of the nanoplatforms, showing significant tumor cell inhibition and killing effect in vivo.

Conclusion

The results showed that the GOx/EC@Fe3O4@CCM nanoplatforms successfully induced significant ferroptosis of Hepatocellular carcinoma cells through a cascade effect, and finally effectively promoted cancer cell regression.

Natural Disinfection-like Process Unveiled in Soil Microenvironments by Enzyme-Catalyzed Chlorination

Substantial natural chlorination processes are a growing concern in diverse terrestrial ecosystems, occurring through abiotic redox reactions or biological enzymatic reactions. Among these, exoenzymatically mediated chlorination is suggested to be an important pathway for producing organochlorines and converting chloride ions (Cl-) to reactive chlorine species (RCS) in the presence of reactive oxygen species like hydrogen peroxide (H2O2). However, the role of natural enzymatic chlorination in antibacterial activity occurring in soil microenvironments remains unexplored. Here, we conceptualized that heme-containing chloroperoxidase (CPO)-catalyzed chlorination functions as a naturally occurring disinfection process in soils. Combining antimicrobial experiments and microfluidic chip-based fluorescence imaging, we showed that the enzymatic chlorination process exhibited significantly enhanced antibacterial activity against Escherichia coli and Bacillus subtilis compared to H2O2. This enhancement was primarily attributed to in situ-formed RCS. Based on semiquantitative imaging of RCS distribution using a fluorescence probe, the effective distance of this antibacterial effect was estimated to be approximately 2 mm. Ultrahigh-resolution mass spectrometry analysis showed over 97% similarity between chlorine-containing formulas from CPO-catalyzed chlorination and abiotic chlorination (by sodium hypochlorite) of model dissolved organic matter, indicating a natural source of disinfection byproduct analogues. Our findings unveil a novel natural disinfection process in soils mediated by indigenous enzymes, which effectively links chlorine-carbon interactions and reactive species dynamics.

In situ H2O2 generation methods in the context of enzyme biocatalysis

Hydrogen peroxide is a versatile oxidant that has use in medical and biotechnology industries. Many enzymes require this oxidant as a reaction mediator in order to undergo their oxygenation chemistries. While there is a reliable method for generating hydrogen peroxide via an anthraquinone cycle, there are several advantages for generating hydrogen in situ. As highlighted in this review, this is particularly beneficial in the case of biocatalysts that require hydrogen peroxide as a reaction mediator because the exogenous addition of hydrogen peroxide can damage their reactive heme centers and render them inactive. In addition, generation of hydrogen peroxide in situ does not dilute the reaction mixture and cause solution parameters to change. The environment would also benefit from a hydrogen peroxide synthesis cycle that does not rely on nonrenewable chemicals obtained from fossil fuels. Generation of hydrogen peroxide in situ for biocatalysis using enzymes, bioelectrocatalyis, photocatalysis, and cold temperature plasmas are addressed. Particular emphasis is given to reaction processes that support high total turnover numbers (TTNs) of the hydrogen peroxide-requiring enzymes. Discussion of innovations in the use of hydrogen peroxide-producing enzyme cascades for antimicrobial activity, wastewater effluent treatment, and biosensors are also included.