Toxins

Human organoids and organ-on-chip/microphysiological systems (OoC/MPS) are increasingly used as new-approach methodologies for biotoxin assessment. They retain human-relevant tissue organization and enable interpretable analysis of exposure geometry, barrier transport, perfusion, and (when needed) multi-organ coupling. In this review, we synthesize primary evidence across major toxin classes, including bacterial enterotoxins (e.g., cholera toxin, heat-stable enterotoxins, Shiga toxins), mycotoxins (e.g., aflatoxin B1, ochratoxin A, deoxynivalenol), and algal/cyanobacterial toxins (e.g., saxitoxin, domoic acid, microcystins, biliatresone). We emphasize studies that clearly define toxin identity and exposure context and that demonstrate mechanism-critical model competencies under assay conditions. We highlight decision-informative functional endpoints that align with the dominant pathophysiology. These include cystic fibrosis transmembrane conductance regulator (CFTR)-dependent secretion in human enteroids/colonoids, transporter-linked proximal tubular injury in kidney MPS, gut–kidney axis injury from Shiga toxin-producing E. coli in microfluidic systems, and multi-electrode array (MEA) network readouts in human 3D neural tissues. We then summarize best practices that improve cross-study comparability. These include reporting delivered versus nominal exposure, assessing recovery/mass balance and device/material interactions, applying proportional biological qualification (polarity, transporter/enzymatic competence, functional stability), defining a minimal comparable endpoint core, and preserving QIVIVE readiness in reporting. Finally, we outline near-term priorities for the field, including chronic low-dose and mixture designs, harmonized reference panels and acceptance criteria, and fit-for-purpose escalation to coupled OoC/MPS only when perfusion or organ–organ coupling is expected to change the interpretation.

Pertussis toxin (PTx) is a major virulence factor of Bordetella pertussis and an AB5-type exotoxin that disrupts host signaling. Its enzymatic A subunit ADP-ribosylates the α-subunit of inhibitory G proteins (Gα_i), preventing them from mediating receptor-induced inhibition of adenylyl cyclase (AC). This leads to unrestrained cAMP accumulation in host cells, a canonical mechanism underlying many pertussis disease manifestations. PTx works in concert with the bacterium’s adenylate cyclase toxin (ACT) to subvert immune defenses and establish infection. Interestingly, PTx exerts both cAMP-dependent and cAMP-independent effects. In addition to the well-known cAMP-mediated pathway, PTx’s B oligomer can engage host cell surface receptors to trigger signaling cascades independent of the A subunit’s catalytic activity. Such B oligomer-mediated pathways modulate cellular responses in the absence of ADP-ribosylation. This review provides a comprehensive analysis of PTx’s dual functionality, distinguishing its G_i protein-dependent elevation of cAMP from the noncanonical activities of the B oligomer. It also highlights how disruption of constitutive G_i signaling and the interplay between PTx and ACT shape host–pathogen interaction in pertussis pathogenesis.

Post-stroke upper limb pain is prevalent and challenging to manage once established. Early use of botulinum toxin can reduce spasticity and contracture development and has potential to prevent or reduce pain. A secondary analysis of the EUBoSS study was undertaken to report pain prevalence in people post-stroke with severe upper limb impairment and spasticity in a hyper/acute setting, identify if botulinum toxin Type-A (BoNTA) could prevent pain developing and reduce pain if already present and evaluate differences in analgesic use between BoNTA and placebo groups. Odds ratios (OR) with 95% confidence intervals (CI) were calculated. Ninety-three participants (48F:45M) were randomised at a median of 11 days post-stroke (IQR 8–19) and included in the intention-to-treat analysis. Pain prevalence increased from 29.0% (95% CI [20.1–37.9%]) to 63.4% (95% CI [54.0–72.9%]) at six months. BoNTA treatment may prevent the development of pain at six months (OR = 0.42, 95% CI [0.18 to 1.01]) but not at three months (OR = 0.57, 95% CI [0.25 to 1.32]). The odds ratio for being on at least one analgesic at six months in the BoNTA group was 0.35 ([95% 0.14 to 0.87]). This secondary analysis suggests that early treatment of spasticity with BoNTA may potentially help prevent post-stroke upper limb pain and reduce analgesic use but appears less effective once pain is established. Further prospective studies are required to verify the hypotheses generated from this secondary analysis.