Poisoning with Soman, an Organophosphorus Nerve Agent, Alters Fecal Bacterial Biota and Urine Metabolites: a Case for Novel Signatures for Asymptomatic Nerve Agent Exposure

Abstract

The experimental pathophysiology of organophosphorus (OP) chemical exposure has been extensively reported. Here, we describe an altered fecal bacterial biota and urine metabolome that follows intoxication with soman, a lipophilic G class chemical warfare nerve agent. Non-anaesthetized Sprague-Dawley male rats were subcutaneously administered soman at 0.8 (sub-seizurogenic) or 1.0 (seizurogenic) of the median lethal dose (LD) and evaluated for signs of toxicity. Animals were stratified based on seizing activity to evaluate effects of soman exposure on fecal bacterial biota and urine metabolites. Soman exposure reshaped fecal bacterial biota by altering ,, , and genera of the and phyla, some of which are known to hydrolyze OPs. However, analogous changes were not observed in the bacterial biota of the ileum, which remained the same irrespective of dose or seizing status of animals after soman intoxication. However, at 75 days post soman exposure, bacterial biota stabilized and no differences were observed between groups. Interestingly, when considering just the seizing status of animals, we found that the urine metabolome was markedly different. Leukotriene C4, kynurenic acid, 5-hydroxyindoleacetic acid, norepinephrine, and aldosterone were excreted at much higher rates at 72 hrs in seizing animals, consistent with early multi-organ involvement during soman poisoning. These findings demonstrate the feasibility of using the dysbiosis of fecal bacterial biota in combination with urine metabolome alterations as forensic evidence for pre-symptomatic OP exposure temporally to enable administration of neuroprotective therapies of the future. The paucity of assays to determine physiologically relevant OP exposure presents an opportunity to explore the use of fecal bacteria as sentinels in combination with urine to assess changes in the exposed host. Recent advances in sequencing technologies and computational approaches have enabled researchers to survey large community level changes of gut bacterial biota and metabolomic changes in various biospecimens. Here, we profiled changes in fecal bacterial biota and urine metabolome following a chemical warfare nerve agent exposure. The significance of this work is a proof-of-concept that fecal bacterial biota and urine metabolites are two separate biospecimens rich in surrogate indicators suitable for monitoring OP exposure. The larger value of such an approach is that assays developed around these observations can be deployed at any setting with a moderate clinical chemistry and microbiology capability. This can enable estimation of the affected radius or to screen, triage, or rule out suspected cases of exposures in mass casualty scenarios, transportation accidents involving hazmats, refugee movements, humanitarian missions, and training settings when coupled to an established and validated decision-tree with clinical features.

Gut dysbiosis following organophosphate, diisopropylfluorophosphate (DFP), intoxication and saracatinib oral administration

“…Soman. exposure increased in the relative abundance of Proteobacteria and Cyanobacteria 72 hours post exposure (Getnet et al, 2018). This was also observed in the current study, specifically at 48 hours post-DFP exposure.…”

“…Notably, DFP-exposed animals eat less in the 2-3 days following DFP intoxication, and therefore lose bodyweight. A number of bacteria have been found to contain genes implicated in metabolism of OPs, which could explain the increase in abundance of Proteobacteria and Cyanobacteria (Karpouzas and Singh, 2006;Getnet et al, 2018). Future studies could determine if any of the genera/species identified in this study are capable of OP metabolism.…”

“…Prior to this study, one other group did observe alterations in the gut microbiome following soman, an OPNA, intoxication (Getnet et al, 2018). DFP is typically used as a surrogate for soman or other OPNAs and has the same mechanism of action and clinical signs upon exposure (Jett, 2012).…”

“…Although our understanding of the neurological consequences of OPNA-induced neurotoxicity has been of great interest in recent decades, less is known about other short-and long-term toxicity in other biological systems including the gut microbiome. One study, showed that there was a significant effect on the fecal bacteria biota and urine metabolites following soman intoxication (Getnet et al, 2018). Until this study, this was an unknown consequence of OPNA toxicity and has not been studied in other models of OPNA intoxication.…”

Soman (GD) Rat Model to Mimic Civilian Exposure to Nerve Agent: Mortality, Video-EEG Based Status Epilepticus Severity, Sex Differences, Spontaneously Recurring Seizures, and Brain Pathology

“…In the latter study, they also administered 3 mg/kg MDZ but at 40 min post-soman. The other three soman studies without pretreatment tested the efficacy of diazepam (10 mg/kg) with 0.8-1.0 LD 50 soman (instead of 1.2 LD 50 ), however, the mortality details were not reported (Schultz et al, 2012(Schultz et al, , 2014Getnet et al, 2018). Recently, we also demonstrated in the rat DFP model that midazolam is more effective than diazepam in preventing mortality (Gage et al, 2021).…”