Impact of low-dose UV-A in Caenorhabditis elegans during candidate bacterial infections.

Ultraviolet radiation is a non-ionizing radiation produced by longer wavelength energy sources with lower frequency and is categorized into UV-A, UV-B, and UV-C. Minimal exposure to this radiation has several health benefits, which include treating microbial contaminations and skin therapies. However, the antimicrobial action of low-dose UV-A during pathogenic bacterial infections is still unrevealed. In this study, the impact of low-dose UV-A as pre- or post-treatment using the model organism, Caenorhabditis elegans with candidate pathogens (Acinetobacter baumannii and Staphylococcus aureus) mediated infections was investigated. The results indicated enrichment of metabolites, reduced level of antioxidants, increased expression of dopamine biosynthesis and transportation, and decrease in serotonin biosynthesis when the organism was exposed to low-dose UV-A for 5 min. This, in turn, elevated the expression of candidate regulatory proteins involved in lifespan determination, innate immunity, and cAMP-response element binding protein (CREB), which appear to increase the lifespan and brood size of C. elegans during A. baumannii and S. aureus infections. The findings suggested that the low-dose UV-A treatment during A. baumannii and S. aureus infections prolonged the lifespan and increased the egg-laying capacity of C. elegans.

Distinct global metabolomic profiles of the model organism Caenorhabditis elegans during interactions with Staphylococcus aureus and Salmonella enterica Serovar Typhi.

The interactive network of hosts with pathogenic microbes is still questionable. It has been hypothesized and reported that the host shows altered regulatory mechanisms for different pathogens. Several studies using transcriptomics and proteomics revealed the altered pathways and sequential regulations displayed by the host during bacterial interactions. Still, there is a gap in understanding the triggering molecule at transcriptomic and proteomic levels due to the lack of the knowledge of the interactive metabolites produced during their interactions. In this study, the global metabolomic approach was performed in the nematode model organism Caenorhabditis elegans upon exposure to a Gram-negative bacteria, Salmonella enterica Serovar Typhi, and a Gram-positive bacteria, Staphylococcus aureus, and the whole metabolome was categorized as endo-metabolome (internally produced) and exo-metabolome (externally releasing). The extracted metabolites were subjected to liquid chromatography mass spectrometry (ESI-LC/qToF-MS/MS). In total 5578, 4554 and 4046 endo-metabolites and 4451, 3625 and 1281 exo-metabolites were identified in C. elegans when exposed to E. coli OP50, S. Typhi and S. aureus, respectively. Both the multivariate and univariate analyses were performed. The variation in endo- and exo-metabolome during candidate bacterial interactions was observed. The results indicated that, during S. aureus interaction, the exclusively enriched metabolites were significantly involved in alpha-linoleic acid metabolism. Similarly, the exclusively enriched metabolites during the interaction of S. Typhi were significantly involved in the phosphatidylinositol signalling system. The whole metabolomic profile presented here will build the scope to understand the role of metabolites and the respective pathways in host response during the early period of bacterial infections.

Cronobacter sakazakii Cue for the Attraction and Its Impact on the Immunity of Caenorhabditis elegans.

Cronobacter sakazakii, an opportunistic foodborne pathogen prevalently detected in contaminated powdered infant formula, is associated with different diseases, including meningitis. It can cross the blood-brain barrier and affects the CNS. The impact of C. sakazakii on host neuronal cells and behavior is largely unknown. Hence, detailed molecular data are required to understand its severity. Caenorhabditis elegans is a unique model for studying chemical communication, as it relies on chemosensation for searching nutritional supplements. Although, C. sakazakii is pathogenic to C. elegans, our analysis indicated that C. elegans was highly attracted toward C. sakazakii compared to its food source, E. coli OP50. To study the cue for the attraction, bioactive components (RNA/Protein/Lipopolysaccharides/Metabolites) of C. sakazakii were isolated and used for observing the chemotaxis behavior of C. elegans. The results signified that C. elegans was more attracted toward acid extracted metabolites than those of the other extraction methods. The combined action of acid extracted metabolites of C. sakazakii and a candidate pathogen drastically reduced the survival of C. elegans. In addition, qPCR analysis suggested that the exposure of isolated metabolites through acid extraction to C. elegans for 24 h modified the candidate immune regulatory genes involved in pathogen recognition and kinase activity such as clec-60, clec-87, lys-7, akt-2, pkc-1, and jnk-1.

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

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.

Proteomic analysis of Caenorhabditis elegans against Salmonella Typhi toxic proteins.

Bacterial effector molecules are crucial infectious agents that can cause pathogenesis. In the present study, the pathogenesis of toxic Salmonella enterica serovar Typhi (S. Typhi) proteins on the model host Caenorhabditis elegans was investigated by exploring the host's regulatory proteins during infection through the quantitative proteomics approach. Extracted host proteins were analyzed using two-dimensional gel electrophoresis (2D-GE) and differentially regulated proteins were identified using MALDI TOF/TOF/MS analysis. Of the 150 regulated proteins identified, 95 were downregulated while 55 were upregulated. The interaction network of regulated proteins was predicted using the STRING tool. Most downregulated proteins were involved in muscle contraction, locomotion, energy hydrolysis, lipid synthesis, serine/threonine kinase activity, oxidoreductase activity, and protein unfolding. Upregulated proteins were involved in oxidative stress pathways. Hence, cellular stress generated by S. Typhi proteins in the model host was determined using lipid peroxidation as well as oxidant and antioxidant assays. In addition, candidate proteins identified via extract analysis were validated by western blotting, and the roles of several crucial molecules were analyzed in vivo using transgenic strains (myo-2 and col-19) and mutant (ogt-1) of C. elegans. To the best of our knowledge, this is the first study to report protein regulation in host C. elegans exposed to toxic S. Typhi proteins. It highlights the significance of p38 MAPK and JNK immune pathways.

Metabolomics: small molecules that matter more.

Metabolomics, an analytical study with high-throughput profiling, helps to understand interactions within a biological system. Small molecules, called metabolites or metabolomes with the size of <1500 Da, depict the status of a biological system in a different manner. Currently, we are in need to globally analyze the metabolome and the pathways involved in healthy, as well as diseased conditions, for possible therapeutic applications. Metabolome analysis has revealed high-abundance molecules during different conditions such as diet, environmental stress, microbiota, and disease and treatment states. As a result, it is hard to understand the complete and stable network of metabolites of a biological system. This review helps readers know the available techniques to study metabolomics in addition to other major omics such as genomics, transcriptomics, and proteomics. This review also discusses the metabolomics in various pathological conditions and the importance of metabolomics in therapeutic applications.

A Paradigm Gap in Host-Pathogen Interaction Studies: Lesson from the COVID-19 Pandemic.

INTRODUCTION: COVID-19 outbreak displayed presumably an increased accumulation of SARS-CoV-2 virus during comorbid complications and a substantial variation in the mortality within and between the countries, which in turn siren us the lack of knowledge in host-pathogen interactions (HPIs). Our aim is to describe the lessons taught by the COVID-19 pandemic in the existing/missing investigations on HPI. METHODS: This was from a retrospective meta-analysis of literature on "COVID-19 and comorbidity" to expose the existing paradigm gap in HPI by highlighting the omitted concepts/areas of research and new approaches to consider for the development of future therapeutics. RESULTS: Literature on "COVID-19 and comorbidity" apparently depicted the disparity in HPI during comorbid/immune-challenged conditions, which was reflected in the poor prognosis of the disease and failed therapeutics upon clinical trials. Moreover, the entry, adherence, multiplication, and the following establishment of infection were also varied in groups with various comorbidities. This edified that the mode of interaction of an infectious agent could vary according to the immunological and health status of the host system and hence the efficiency/success rate of treatment modalities. In addition, limited number of literature on HPI upon comorbid and immune-challenged conditions of the host manifestly indicated that there is a lack of our focus/attention on consideration of the host immune/health-specific factors in HPI studies. These alert us that the development of unambiguous therapeutic approaches is needed for a better/successful treatment of novel infectious agents in the future. CONCLUSION: By understanding the immunological state exhibited in SARS-CoV-2 infection, we conclude that the COVID-19 pandemic has taught us a great lesson that our current understanding of HPI is insufficient to fight and conquer novel infections in real life. Hence, newer approaches are obligatory to understand HPI in order to combat COVID-19-like outbreaks in the future, if any, and also to design novel immunogenic/nutraceutical-based therapeutics.