Impact of Hypervirulent C. difficile TcdB2 on Enteric Neurons and Neurotransmitters

Overview

This study demonstrates that the TcdB2 toxin from hypervirulent Clostridioides difficile directly induces dose-dependent cytopathic effects on enteric neurons in vitro and in adult mouse colons. Additionally, TcdB2 alters neurotransmitter expression by increasing choline acetyltransferase and neural nitric oxide synthase prior to neuronal loss, indicating both neuronal damage and neurotransmitter composition changes in the enteric nervous system during infection.

Background

Clostridioides difficile infection (CDI) is a leading cause of intestinal infections with significant morbidity and mortality, especially due to hypervirulent strains producing toxin B (TcdB). The enteric nervous system (ENS) regulates intestinal functions such as motility and secretion, but the effects of CDI toxins on intrinsic ENS neurons remain poorly understood. TcdB is a major virulence factor that disrupts cellular function by glucosylating GTPases, leading to cell death. This study investigates the direct impact of the TcdB2 variant from hypervirulent strains on enteric neurons and neurotransmitter dynamics.

Data Highlights

Approximately 60 adult and 30 postnatal C57BL/6J mice were used for in vivo and in vitro experiments. TcdB2 was cloned, expressed, and purified for experimental use. Enteric neurospheres derived from postnatal mouse colons were treated with TcdB2, demonstrating dose-dependent neuronal cytopathy. Increased expression of choline acetyltransferase (ChAT) and neural nitric oxide synthase (nNOS) was observed prior to neuronal loss, both in vitro and in vivo.

Key Findings

• TcdB2 from hypervirulent C. difficile induces dose-dependent cytopathic effects on enteric neurons in vitro and in adult mouse colons.
• Prior to neuronal loss, TcdB2 treatment increases expression of neurotransmitter-related enzymes choline acetyltransferase (ChAT) and neural nitric oxide synthase (nNOS) in colonic neurons.
• TcdB2 acts via the tissue factor pathway inhibitor (TFPI) receptor to mediate its effects on enteric neurons.
• Neuronal loss and neurotransmitter alterations suggest that CDI impacts both neuronal integrity and neurotransmitter composition in the ENS.
• These findings highlight a direct neurotoxic effect of TcdB2 on intrinsic enteric neurons, distinct from previously described effects on extrinsic sensory neurons.

Clinical Implications

Understanding that TcdB2 directly damages enteric neurons and alters neurotransmitter expression provides insight into the pathophysiology of CDI-related intestinal dysfunction. Therapeutic strategies targeting TcdB2 or its receptor interactions may help preserve enteric neuronal integrity and maintain gastrointestinal function during infection. Additionally, monitoring neurotransmitter changes could serve as a biomarker for early neuronal involvement in CDI.

Conclusion

The hypervirulent C. difficile TcdB2 toxin directly compromises enteric neuronal integrity and modulates neurotransmitter enzyme expression, contributing to ENS dysfunction during infection. These findings expand the understanding of CDI pathogenesis by implicating intrinsic enteric neurons as direct targets of TcdB2 toxicity.

References

1. Author/Source/Year -- Impact of TcdB from Hypervirulent Clostridioides difficile on Neuronal Integrity and Neurotransmitter Dynamics in the Enteric Nervous System