Physiological and Metabolite Alterations Associated with Neuronal Signals of Caenorhabditis elegans during Cronobacter sakazakii Infections

Abstract

Metabolomic reprogramming plays a crucial role in the activation of several regulatory mechanisms including neuronal responses of the host. In the present study, alterations at physiological and biochemical levels were initially assessed to monitor the impact of the candidate pathogen Cronobacter sakazakii on the nematode host Caenorhabditis elegans. The abnormal behavioral responses were observed in infected worms in terms of hyperosmolarity and high viscous chemicals. The microscopic observations indicated reduction in egg laying and internal hatching of larvae in the host. An increased level of total reactive oxygen species and reduction in antioxidant agents such as glutathione and catalase were observed. These observations suggested the severe effect of C. sakazakii infection on C. elegans. To understand the small molecules which likely mediated neurotransmission, the whole metabolome of C. elegans during the infection of C. sakazakii was analyzed using liquid chromatography−mass spectrometry. A decrease in the quantity of methyl dopamine and palmitoyl dopamine and an increase in hydroxyl dopamine suggested that reduction in dopamine reuptake and dopamine neuronal stress. The disordered dopaminergic transmission during infection was confirmed using transgenic C. elegans by microscopic observation of Dat-1 protein expression. In addition, reduction in arachidonic acid and short-chain fatty acids revealed their effect on lipid droplet formation as well as neuronal damage. An increase in the quantity of stearoyl CoA underpinned the higher accumulation of lipid droplets in the host. On the other hand, an increased level of metabolites such as palmitoyl serotonin, citalopram N-oxide, and N-acyl palmitoyl serotonin revealed serotonin-mediated potential response for neuroprotection, cytotoxicity, and cellular damage. Based on the metabolomic data, the genes correspond to small molecules involved in biosynthesis and transportation of candidate neurotransmitters were validated through relative gene expression.

Cronobacter sakazakii infection implicates multifaceted neuro-immune regulatory pathways of Caenorhabditis elegans

“…24 Later, Muthubharathi et al reported that the metabolites of C. elegans respond negatively to C. sakazakii infection. 25 Further studies also proved that C. sakazakii infection altered the genes of C. elegans involved in pathogen recognition and kinase activity. 26 Despite this limited number of studies, no reports are available regarding the neuro-immune protein change in C. elegans during C. sakazakii infection to date.…”

“…In studies of C. sakazakii interactions, C. elegans has been used as a host. [23][24][25][26] Albeit the transcriptional and metabolomic level studies have been reported by our research group, we aimed to approach more specifically to the functional molecular players involved in crucial neuro-immune signaling pathways. The protein players integrated into the immune system via neuronal signals rapidly contribute to the defense mechanism during the HPI.…”

Application of Caenorhabditis elegans in Lipid Metabolism Research

“…Using the Cortecs C18 column, a reversed-phase LC-MS (RP-LC-MS) was performed, showing that the improved combined extraction scheme for lipid and metal species allowed for the simultaneous monitoring and analysis of the lipidomes of the same nematode population, especially iron redox state homeostasis [ 242 ]. Through the LC-MS/MS method, Muthubharathi et al found that a sakazakii infection made the nematode neurotransmitters and fatty acids abnormal, which was associated with the accumulation of LD [ 243 ]. In addition, LC-MS and multiple reaction monitoring (MRM) were also combined to fully characterize the composition and abundance of sphingolipids (SLs) under different developmental stages and growth conditions in nematodes.…”

Distinct global metabolomic profiles of the model organismCaenorhabditis elegansduring interactions withStaphylococcus aureusandSalmonella entericaSerovar Typhi

“…The protocol was followed as mentioned in ref. 32. The synchronized L4 stage worms were washed with a M9 buffer.…”

“…For analyzing the whole metabolome, the metabolites were categorized into endo-metabolome, the metabolites present in the host (also called metabolic fingerprinting), and exo-metabolome, the metabolites secreted out by the host (also called metabolic footprinting). 32 By studying both, the complete profile of metabolites which are synthesized, utilized and secreted out during the interaction of bacteria in C. elegans can be understood. The results indicated that significantly distinct profiles in both endo- and exo-metabolome of C. elegans during S. aureus and S. Typhi interactions could be useful to identify the therapeutic targets in developing bioactives/drugs for metabolic pathway(s) or player(s).…”