The homeodomain transcription factor CEH-37 regulates PMK-1/p38 MAPK pathway to protect against intestinal infection via the phosphatase VHP-1

Asperuloside promotes innate immunity via IRE-1/XBP-1 mediated unfolded protein response

Numerous studies have reported that asperuloside (ASP), a monomeric compound extracted from the traditional Chinese medicine Spreading Hedyotis Herb, possesses a variety of medicinal properties, including the treatment of obesity, cancer, inflammatory diseases, and bacterial infections. However, its role in innate immunity and the underlying mechanisms of action remain largely unexplored. Protein homeostasis and the health of the endoplasmic reticulum (ER) are crucial for organismal function, as a well-balanced ER is essential not only for maintaining cellular integrity but also for ensuring immune homeostasis. In this study, we demonstrated that asperuloside enhances the resistance of Caenorhabditis elegans to the human opportunistic pathogen Pseudomonas aeruginosa PA14 and reduces the bacterial load within its intestine. Additionally, asperuloside promotes innate immunity by activating the IRE-1/XBP-1 signaling pathway. Furthermore, asperuloside protects A549 human lung epithelial cells and mice against PA14 infection through the IRE-1/XBP-1 signaling pathway. Our findings indicate that the ability of asperuloside to promote innate immunity is conserved across invertebrates and mammals, offering new insights for the future development of antibacterial drugs.

Berberine hydrochloride enhances innate immunity to protect against pathogen infection via p38 MAPK pathway

The p38 MAPK pathway, an evolutionarily conserved mechanism, plays a crucial role in defending hosts against bacterial infections in both mammals and nematodes. Activating p38 MAPK signaling has been identified as a promising strategy to strengthen innate immunity and enhance resistance to pathogenic infections across various organisms.Berberine hydrochloride (BH), an isoquinoline alkaloid derived from Coptis, is known for its diverse biological activities, including anticancer, antibacterial, anti-inflammatory, lipid-lowering, and hepatoprotective effects. However, its impact on innate immunity and the associated molecular mechanisms remains unclear. In this study, we discovered that 10 μM Berberine hydrochloride enhanced resistance against both Gram-negative pathogens, such as Pseudomonas aeruginosa, Salmonella enterica and Gram-positive pathogen Listeria monocytogenes. Notably, Berberine hydrochloride improved pathogen resistance by reducing bacterial load in the intestine. Screening of classical innate immune pathways in Caenorhabditis elegans revealed that Berberine hydrochloride conferred protection against infections through the p38 MAPK pathway, specifically by activating p38/PMK-1 signaling in the intestine to bolster innate immunity. Furthermore, Berberine hydrochloride also stimulated innate immunity in mice via the p38 MAPK pathway and significantly reduced bacterial load in the lungs. These findings indicate that Berberine hydrochloride may have therapeutic potential for protecting host from infectious diseases.

The Roles of Distinct Transcriptional Factors in the Innate Immunity of C. elegans

Deleterious molecules or factors produced by pathogens can hinder the normal physiological functioning of organisms. In response to these survival challenges, organisms rely on innate immune signaling as their first line of defense, which regulates immune-responsive genes and antimicrobial peptides to protect against pathogenic infections. These genes are under the control of transcription factors, which are known to regulate the transcriptional activity of genes after binding to their regulatory sequences. Previous studies have employed Caenorhabditis elegans as a host-pathogen interaction model to demonstrate the essential role of different transcription factors in the innate immunity of worms. In this review, we summarize the advances made regarding the functioning of distinct transcription factors in the innate immune response upon pathogen infection. Finally, we discuss the open questions in the field, whose resolutions have the potential to expand our understanding of the mechanisms underlying the innate immunity of organisms.

Chlorogenic acid inhibits Pseudomonas toxin pyocyanin and activates mitochondrial UPR to protect host against pathogen infection

Mitochondria are required for protecting host against pathogenic bacteria by activating mitochondrial unfolded protein response (UPRmt). Chlorogenic acid (CGA), a phenolic acid compound of green coffee extracts and tea has been shown to exhibit activities such as antioxidant, antibacterial, hepatoprotective, cardioprotective, anti-inflammatory, neuroprotective, anti-obesity. However, whether CGA regulates innate immunity and the underlying molecular mechanisms remain unknown. In this study, we found that CGA increased resistance to Gram-negative pathogen Pseudomonas aeruginosa PA14 in dose dependent manner. Meanwhile, CGA enhanced innate immunity in Caenorhabditis elegans by reducing intestinal bacterial burden. CGA also inhibited the proliferation of pathogenic bacteria. Importantly, CGA inhibited the production of Pseudomonas toxin pyocyanin (PYO) to protect C. elegans from P. aeruginosa PA14 infection. Furthermore, CGA activated the UPRmt and expression of antibacterial peptide genes to promote innate immunity in C. elegans via transcription factor ATFS-1(activating transcription factor associated with stress-1). Unexpectedly, CGA enhanced innate immunity independently of other known innate immune pathways. Intriguingly, CGA also protected mice from P. aeruginosa PA14 infection and activated UPRmt. Our work revealed a conserved mechanism by which CGA promoted innate immunity and boosted its therapeutic application in the treatment of pathogen infection.

DEAD-box RNA helicase DDX-23 mediates dietary restriction induced health span in Caenorhabditis elegans

Dietary restriction (DR) extends lifespan in diverse species, from yeast to mammals. However, its underlying mechanisms are not well understood. In this study, through using the tractable model Caenorhabditis elegans, we show a role for the DEAD-box RNA helicase, DDX-23 (homologous to mammal DDX23) as a regulator of healthspan in response to dietary restriction. Meanwhile, DDX-23 is also required for heat and oxidative stress response in C. elegans. Intriguingly, DDX-23 functions in the germline during adult to regulate dietary restriction-induced longevity. We then find that PHA-4/FOXA acts downstream of DDX-23 to mediate the transcriptional response of SOD-related genes and consequently the lifespan of the animals. Furthermore, we find that the DEAD-box RNA helicase, DDX-23 negatively regulates the healthy lifespan extension by up-regulating the expression of miR-231, and resulting in suppressing the activation of FOXO transcription factor DAF-16. Our work shows a newly discovered for DEAD-box RNA helicase DDX-23 in the regulation of dietary restriction-mediated longevity in C. elegans and reveals the downstream transcriptional regulation mechanisms.

Modulation by NPY/NPF-like receptor underlies experience-dependent, sexually dimorphic learning

The evolutionary paths taken by each sex within a given species sometimes diverge, resulting in behavioral differences. Given their distinct needs, the mechanism by which each sex learns from a shared experience is still an open question. Here, we reveal sexual dimorphism in learning: C. elegans males do not learn to avoid the pathogenic bacteria PA14 as efficiently and rapidly as hermaphrodites. Notably, neuronal activity following pathogen exposure was dimorphic: hermaphrodites generate robust representations, while males, in line with their behavior, exhibit contrasting representations. Transcriptomic and behavioral analysis revealed that the neuropeptide receptor npr-5, an ortholog of the mammalian NPY/NPF-like receptor, regulates male learning by modulating neuronal activity. Furthermore, we show the dependency of the males' decision-making on their sexual status and demonstrate the role of npr-5 as a modulator of incoming sensory cues. Taken together, these findings illustrate how neuromodulators drive sex-specific behavioral plasticity in response to a shared experience.

Paired C-type lectin receptors mediate specific recognition of divergent oomycete pathogens in C. elegans

Innate immune responses can be triggered upon detection of pathogen- or damage-associated molecular patterns by host receptors that are often present on the surface of immune cells. While invertebrates like Caenorhabditis elegans lack professional immune cells, they still mount pathogen-specific responses. However, the identity of host receptors in the nematode remains poorly understood. Here, we show that C-type lectin receptors mediate species-specific recognition of divergent oomycetes in C. elegans. A CLEC-27/CLEC-35 pair is essential for recognition of the oomycete Myzocytiopsis humicola, while a CLEC-26/CLEC-36 pair is required for detection of Haptoglossa zoospora. Both clec pairs are transcriptionally regulated through a shared promoter by the conserved PRD-like homeodomain transcription factor CEH-37/OTX2 and act in sensory neurons and the anterior intestine to trigger a protective immune response in the epidermis. This system enables redundant tissue sensing of oomycete threats through canonical CLEC receptors and host defense via cross-tissue communication.

S-Adenosylmethionine (SAM) diet promotes innate immunity via histone H3K4me3 complex

S-adenosylmethionine (SAM) was a methyl donor for modifying histones, which had crucial roles in lipid accumulation, tissue injury, and immune responses. SAM fluctuation might be linked to variations in histone methylation. However, the underlying molecular mechanisms of whether the SAM diet influenced the immune response via histone modification remained obscure. In this study, we utilized the Caenorhabditis elegans as a model to investigate the role of SAM diet in innate immunity. We found that 50 μM SAM increased resistance to Gram-negative pathogen Pseudomonas aeruginosa PA14 by reducing the bacterial burden in the intestine. Furthermore, through the genetic screening in C. elegans, we found that SAM functioned in germline to enhance innate immunity via an H3K4 methyltransferase complex to upregulate the immune response genes, including irg-1 and T24B8.5. Intriguingly, SAM also protected mice from P. aeruginosa PA14 infection by reducing the bacterial burden in lung. These findings provided insight into the mechanisms of molecular connections among SAM diet, histone modifications and innate immunity.

Schisandrin A enhances pathogens resistance by targeting a conserved p38 MAPK pathway

Schizandrin A (SA), also known as deoxyschizandrin, is one of the most biologically active lignans isolated from the traditional Chinese medicine Fructus schisandrae chinensis. Schisandrin A has proven benefits for anti-cancer, anti-inflammation, hepatoprotection, anti-oxidation, neuroprotection, anti-diabetes. But the influence of Schisandrin A to the innate immune response and its molecular mechanisms remain obscure. In this study, we found that Schisandrin A increased resistance to not only the Gram-negative pathogens Pseudomonas aeruginosa and Salmonella enterica but also the Gram-positive pathogen Listeria monocytogenes. Meanwhile, Schisandrin A protected the animals from the infection by enhancing the tolerance to the pathogens infection rather than by reducing the bacterial burden. Through the screening of the conserved immune pathways in Caenorhabditis elegans, we found that Schisandrin A enhanced innate immunity via p38 MAPK pathway. Furthermore, Schisandrin A increased the expression of antibacterial peptide genes, such as K08D8.5, lys-2, F35E12.5, T24B8.5, and C32H11.12 by activation PMK-1/p38 MAPK. Importantly, Schisandrin A-treated mice also enhanced resistance to P. aeruginosa PA14 infection and significantly increased the levels of active PMK-1. Thus, promoted PMK-1/p38 MAPK-mediated innate immunity by Schisandrin A is conserved from worms to mammals. Our work provides a conserved mechanism by which Schisandrin A enhances innate immune response and boosts its therapeutic application in the treatment of infectious diseases.