Anti-inflammatory effects of FS48, the first potassium channel inhibitor from the salivary glands of the flea Xenopsylla cheopis

The first Ranatuerin antimicrobial peptide with LPS-neutralizing and anti-inflammatory activities in vitro and in vivo

Pelophylax nigromaculata, common traditional Chinese medicinal material used for several hundreds of years, is one of the most widely distributed amphibians in China. In this study, a novel Ranatuerin-2 family antimicrobial peptide, Rana-2PN, was identified and characterized from its skin, and its structural characteristics and functional activities were studied extensively. First, Rana-2PN exhibited a broad spectrum of antimicrobial activity, displaying minimum inhibitory concentration (MIC) values ranging from 12.5 to 100 μM against all strains tested. Mechanistically, Rana-2PN exerted its bacteriostatic effects by binding to bacterial cells and inducing bacterial membrane rupture and subsequent bacterial death. Secondly, Rana-2PN effectively inhibited the inflammatory response in RAW264.7 cells induced by lipopolysaccharide (LPS) and reduced inflammation induced by carrageenan in mouse toes. Thus, Rana-2PN with LPS-neutralizing, anti-inflammatory, and antimicrobial properties, represents the first member of the Ranatuerin antimicrobial peptide family, and its discovery offers a promising therapeutic candidate for addressing inflammatory disorders resulting from bacterial infections.

Insight into a multifunctional potassium channel Kv1.3 and its novel implication in chronic kidney disease

Chronic kidney disease (CKD), a global public health problem, causes substantial morbidity and mortality worldwide. Innovative therapeutic strategies to mitigate the progression of CKD are needed due to the limitations of existing treatments. Kv1.3, a voltage-gated potassium ion channel, plays a crucial role in multiple biological processes, including cell proliferation, apoptosis, energy homeostasis, and migration. Inhibition of the Kv1.3 channels has shown beneficial effects in the therapy of a wide range of human diseases such as cancer, autoimmune and neuroinflammatory diseases. Increasing evidence reveals a close link between Kv1.3 and CKD. This review summarises the most recent insights into the physiological functions of the Kv1.3 channel and its pharmacological modulators. Furthermore, the therapeutic potential of targeting Kv1.3 for CKD is also discussed. Collectively, these studies suggested that Kv1.3 channels may serve as a novel target for CKD therapy.

Ion channels in macrophages: Implications for disease progression

RATIONALE

Macrophages are immune cells found throughout the body and exhibit morphological and functional diversity. Macrophages have been implicated in a wide range of diseases, including autoimmune diseases, acute liver injury, cardiovascular diseases, lung diseases and tumours. Ion channels are transmembrane glycoproteins with important functions in maintaining homeostasis in the intra- and extracellular environment and mediating signal transduction. Many studies have shown that different types of ion channels influence the role of macrophages in the development of various diseases. In recent years, studies on the role of ion channels in macrophages in immune regulation and inflammatory responses have attracted much attention.

OBJECTIVE AND FINDINGS

In order to gain a deeper understanding of the role of macrophage ion channels, this paper reviews the recent research progress on the role of macrophage ion channels in recent years. The aim is to explore the role of different ion channels in the regulation of macrophage function and their impact on a variety of disease processes. The most studied channels are calcium, sodium and potassium channels, most of which are located in the cell membrane. Among these, TRP channels have a more complex role in M1 and M2 macrophage types.

CONCLUSION

Ion channels are critical for the functional regulation of macrophages. Targeting ion channels provides new avenues for disease prevention and treatment. This review provides researchers with new ideas and introduces readers to the current state of research on ion channels in macrophages.

Cath-HG improves the survival rates and symptoms in LPS-induced septic mice due to its multifunctional properties

The clinical syndrome of sepsis arises from severe infection, triggering an abnormal immune response that can lead to multiple organ dysfunction and ultimately the death of the host. Current therapies for sepsis are often limited in efficacy and fail to target the complex interplay of infection, inflammation and coagulation, leading to high mortality rates, which underscores the urgent need for novel therapeutics to combat sepsis. We previously identified Cath-HG, a compound capable of alleviating platelet dysfunction by suppressing GPVI-mediated platelet activation, thereby improving the survival of septic mice subjected to cecal ligation and puncture. Here, we further explored the antimicrobial, anti-inflammatory, LPS-neutralizing and anticoagulant properties of Cath-HG, as well as its protective effects in LPS-induced septic mice. Our results demonstrated that Cath-HG can bind to LPS, aggregate bacteria, and disrupt bacterial cell membranes, subsequently resulting in microbial death. Unlike most other Cathelicidins, Cath-HG displayed anticoagulation properties by regulating the enzymes plasmin, thrombin, β-tryptase, chymase and tissue plasminogen activator. In septic mice, Cath-HG provided protection against sepsis induced by LPS injection and exhibited bactericidal killing, LPS neutralization and inhibition of coagulation and MAPK signal transduction. Furthermore, Cath-HG obviously reduced the expression of pro-inflammatory cytokines and improved the pathological manifestations of tissue injury across multiple organs. Thus, Cath-HG emerges as a promising drug candidate for protecting against sepsis.

Metabolism and immune responses of striped hamsters to ectoparasite challenges: insights from transcriptomic analysis

Introduction

The striped hamster, often parasitized by ectoparasites in nature, is an ideal model for studying host-ectoparasite molecular interactions. Investigating the response to ectoparasites under laboratory conditions helps elucidate the mechanism of host adaptations to ectoparasite pressure.

Methods

Using transcriptome sequencing, we analyzed gene expression in striped hamsters after short-term (3 days) and long-term (28 days) flea (Xenopsylla cheopis) parasitism. Differentially expressed genes (DEGs) were identified and subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. Hub genes were pinpointed using protein-protein interaction (PPI) network analysis and the MCODE in Cytoscape. Gene Set Enrichment Analysis (GSEA) was used to further clarify the functional pathways of these hub genes. Validation of DEGs was performed via RT-qPCR. Additionally, the concentrations of reactive oxygen species (ROS), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were determined using specific enzyme-linked immunosorbent assay (ELISA) detection kits for hamsters.

Results

GO analysis revealed that during early parasitism, hosts primarily responded to the ectoparasites by adjusting the expression of genes related to metabolic functions. As parasitism persisted, the immune response became prominent, activating various immune pathways against ectoparasites. KEGG analysis confirmed the ongoing roles of metabolism and immunity. Notably, the chemical carcinogenesis - reactive oxygen species pathway was upregulated during flea parasitism, with downregulation of hub genes ATP5MC1 and ATP5MC2, highlighting the importance of mitochondrial function in oxidative stress. ELISA findings revealed that on day 3, flea parasitism groups showed elevated ROS expression and reduced SOD and CAT levels compared to the control group. By day 28, only SOD expression showed a significant decrease in both parasitism groups.

Conclusion

This study uncovered the dynamic changes in metabolism and immune responses of striped hamsters parasitized by Xenopsylla cheopis. Hosts adjust their physiological and immune states to optimize survival strategies during different ectoparasite stages, enhancing our understanding of host-ectoparasite interactions. This also paves the way for further research into how hosts regulate complex biological processes in response to ectoparasite challenges.

The role of potassium ion channels in chronic sinusitis

Chronic sinusitis is a common inflammatory disease of the nasal and sinus mucosa, leading to symptoms such as nasal congestion, runny nose, decreased sense of smell, and headache. It often recurs and seriously affects the quality of life of patients. However, its pathological and physiological mechanisms are not fully understood. In recent years, the role of potassium ion channels in the regulation of mucosal barrier function and inflammatory cell function has received increasing attention. In chronic sinusitis, there are often changes in the expression and function of potassium channels, leading to mucosal damage and a stronger inflammatory response. However, the related research is still in its early stages. This article will review the role of the potassium channel in the pathological and physiological changes of chronic sinusitis. The studies revealed that BK/TREK-1 potassium channel play a protective role in the nasal mucosal function through p38-MAPK pathway, and KCa3.1/Kv1.3 enhance the inflammatory response of Chronic rhinosinusitis by regulating immune cell function, intracellular Ca2+ signaling and ERK/MAPK/NF-κB pathway. Because ion channels are surface proteins of cell membranes, they are easier to intervene with drugs, and the results of these studies may provide new effective targets for the prevention and treatment of chronic sinusitis.

Transcriptome analysis of Kunming mice responses to the bite of Xenopsylla cheopis

BACKGROUND

Flea bites could trigger a series of complex molecular responses in the host. However, our understanding of the responses at the molecular level is still relatively limited. This study quantifies the changes in gene expression in mice after flea bites by RNA sequencing (RNA-seq) from their spleens, revealing the potential biological effects of host response to flea bites.

METHODS

RNA-seq was used for transcriptome analysis to screen for differentially expressed genes (DEGs) between the control mice group and the flea bite mice group. Gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed on DEGs. Protein-protein interaction (PPI) network analysis on DEGs related to immune processes was performed. Finally, we randomly selected several genes from the screened DEGs to validate the results from the transcriptome data by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR).

RESULTS

A total of 521 DEGs were identified, including 277 upregulated and 244 downregulated. There were 258 GO terms significantly enriched by upregulated DEGs and 419 GO terms significantly enriched by downregulated DEGs. Among the upregulated DEGs, 22 GO terms were associated with immune cells (e.g., B cells and T cells) and immune regulatory processes, while among the downregulated DEGs, 58 GO terms were associated with immune cells and immune regulatory processes. Through PPI analysis, we found that CD40 molecules with significantly downregulated expression levels after flea bites may play an important role in host immune regulation. Through KEGG pathway enrichment analysis, a total of 26 significantly enriched KEGG pathways were identified. The RT-qPCR analysis results indicated that the transcriptome sequencing results were reliable.

CONCLUSIONS

Through in-depth analysis of transcriptome changes in mice caused by flea bites, we revealed that flea bites could stimulate a series of biological and immunological responses in mice. These findings not only provided a deeper understanding of the impact of flea bites on the host but also provided a basis for further research on the interaction between ectoparasites and the host. We believe that digging deeper into the significance of these transcriptome changes will help reveal more about the adaptive response of the host to ectoparasites.

FS145, the first flea-derived disintegrin, inhibits angiogenesis through specifically binding integrin αvβ3

FS145, a protein containing a WGD motif, was previously described from the salivary transcriptome of the flea Xenopsylla cheopis. Nevertheless, its biological function and complete structure are still uncertain. Herein, FS145 was confirmed to adopt a common αββ structure with the WGD motif exposed on its surface and located right at the top of a loop composed of residues 72-81. Furthermore, FS145 dose-dependently inhibited the proliferation, adhesion, migration, and tube formation of HUVECs by not only binding to integrin αvβ3 but also by subsequently inactivating the FAK/Src/MAPK pathway along with the reduction of the expression of MMP-2, MMP-9, VEGFA, bFGF, Ang2, Tie2, HIF-1α, and FAK. Moreover, FS145 also inhibited aortic vessel sprout and showed strong anti-angiogenic activities as assessed ex vivo, by employing the rat aortic ring assay, chick embryo chorioallantoic membrane, and zebrafish embryo models. Altogether, our results suggest that FS145 suppresses angiogenesis ex vivo and in vitro by blocking integrin αvβ3. The current study reveals the first anti-angiogenesis disintegrin with WGD motif from invertebrates and provides a beneficial pharmacological activity to inhibit abnormal angiogenesis.

Kv1.3 in the spotlight for treating immune diseases

INTRODUCTION

Kv1.3 is the main voltage-gated potassium channel of leukocytes from both the innate and adaptive immune systems. Channel function is required for common processes such as Ca2+ signaling but also for cell-specific events. In this context, alterations in Kv1.3 are associated with multiple immune disorders. Excessive channel activity correlates with numerous autoimmune diseases, while reduced currents result in increased cancer prevalence and immunodeficiencies.

AREAS COVERED

This review offers a general view of the role of Kv1.3 in every type of leukocyte. Moreover, diseases stemming from dysregulations of the channel are detailed, as well as current advances in their therapeutic research.

EXPERT OPINION

Kv1.3 arises as a potential immune target in a variety of diseases. Several lines of research focused on channel modulation have yielded positive results. However, among the great variety of specific channel blockers, only one has reached clinical trials. Future investigations should focus on developing simpler administration routes for channel inhibitors to facilitate their entrance into clinical trials. Prospective Kv1.3-based treatments will ensure powerful therapies while minimizing undesired side effects.

Acid phosphatase-like proteins, a biogenic amine and leukotriene-binding salivary protein family from the flea Xenopsylla cheopis

The salivary glands of hematophagous arthropods contain pharmacologically active molecules that interfere with host hemostasis and immune responses, favoring blood acquisition and pathogen transmission. Exploration of the salivary gland composition of the rat flea, Xenopsylla cheopis, revealed several abundant acid phosphatase-like proteins whose sequences lacked one or two of their presumed catalytic residues. In this study, we undertook a comprehensive characterization of the tree most abundant X. cheopis salivary acid phosphatase-like proteins. Our findings indicate that the three recombinant proteins lacked the anticipated catalytic activity and instead, displayed the ability to bind different biogenic amines and leukotrienes with high affinity. Moreover, X-ray crystallography data from the XcAP-1 complexed with serotonin revealed insights into their binding mechanisms.

BmKK2, a thermostable Kv1.3 blocker from Buthus martensii Karsch (BmK) scorpion, inhibits the activation of macrophages via Kv1.3-NF-κB- NLPR3 axis

ETHNOPHARMACOLOGICAL RELEVANCE

Inflammation plays pivotal role in the development of chronic diseases. Reducing chronic inflammation is an important strategy for preventing and managing many chronic diseases. In traditional Chinese medicine, the processed Buthus martensii Karsch (BmK) scorpion(also called "Quanxie") has been used to treat chronic inflammatory arthritis and spondylitis for hundreds of years suggests that "Quanxie" could potentially be utilized as a resource for identifying new anti-inflammatory compounds. However, the molecular basis and the underline mechanism for the anti-inflammatory effect of processed BmK scorpion are still unclear.

AIM OF THE STUDY

The study aims to determine the potential involvement of macrophage-expressed Kv1.3 in the anti-inflammatory effect of processed BmK scorpion venom, as well as to identify new Kv1.3 blockers derived from processed BmK scorpion.

MATERIALS AND METHODS

In this study, the in vivo and in vitro anti-inflammatory activities were determined using carrageenan-induced paw edema, LPS-induced sepsis mouse models and LPS-induced macrophage activation model respectively. The effect of processed BmK scorpion water extract, processed BmK venom and BmKK2 on different potassium channels were detected by whole-cell voltage-clamp recordings on transfected HEK293 cells or mouse BMDMs. The cytokines were detected using RT-PCR and competitive enzyme-linked immunosorbent assay. High performance liquid chromatography, SDS-PAGE and peptide Mass Spectrometry analysis were used to isolate and identify the BmKK2. SiRNA, western blotting and flow cytometry were used to analysis the anti-inflammatory mechanism of BmKK2.

RESULTS

Here we demonstrate that BmKK2, a thermostable toxin targeting Kv1.3 is the critical anti-inflammatory component in the processed BmK scorpion. BmKK2 inhibits inflammation by targeting and inhibiting the activity of macrophage Kv1.3, thereby inhibiting the activation of NF-kB-NLPR3 pathway and the subsequent release of inflammatory factors.

CONCLUSIONS

These findings provide new insights into the molecular basis of the anti-inflammatory effects of "Quanxie" and highlight the importance of targeting Kv1.3 expressed on macrophages as an anti-inflammatory approach.

The in vitro anticancer effects of FS48 from salivary glands of Xenopsylla cheopis on NCI-H460 cells via its blockage of voltage-gated K+ channels

Voltage-gated K⁺ (K_v) channels play a role in the cellular processes of various cancer cells, including lung cancer cells. We previously identified and reported a salivary protein from the Xenopsylla cheopis, FS48, which exhibited inhibitory activity against K_v1.1-1.3 channels when assayed in HEK 293T cells. However, whether FS48 has an inhibitory effect on cancer cells expressing Kv channels is unclear. The present study aims to reveal the effects of FS48 on the K_v channels and the NCI-H460 human lung cancer cells through patch clamp, MTT, wound healing, transwell, gelatinase zymography, qRT-PCR and WB assays. The results demonstrated that FS48 can be effective in suppressing the K_v currents, migration, and invasion of NCI-H460 cells in a dose-dependent manner, despite the failure to inhibit the proliferation. Moreover, the expression of K_v1.1 and K_v1.3 mRNA and protein were found to be significantly reduced. Finally, FS48 decreases the mRNA level of MMP-9 while increasing TIMP-1 mRNA level. The present study highlights for the first time that blood-sucking arthropod saliva-derived protein can inhibit the physiological activities of tumour cells via the Kv channels. Furthermore, FS48 can be taken as a hit compound against the tumour cells expressing K_v channels.

Revisiting the sialome of the cat flea Ctenocephalides felis

The hematophagous behaviour emerged independently in several instances during arthropod evolution. Survey of salivary gland and saliva composition and its pharmacological activity led to the conclusion that blood-feeding arthropods evolved a distinct salivary mixture that can interfere with host defensive response, thus facilitating blood acquisition and pathogen transmission. The cat flea, Ctenocephalides felis, is the major vector of several pathogens, including Rickettsia typhi, Rickettsia felis and Bartonella spp. and therefore, represents an important insect species from the medical and veterinary perspectives. Previously, a Sanger-based sialome of adult C. felis female salivary glands was published and reported 1,840 expressing sequence tags (ESTs) which were assembled into 896 contigs. Here, we provide a deeper insight into C. felis salivary gland composition using an Illumina-based sequencing approach. In the current dataset, we report 8,892 coding sequences (CDS) classified into 27 functional classes, which were assembled from 42,754,615 reads. Moreover, we paired our RNAseq data with a mass spectrometry analysis using the translated transcripts as a reference, confirming the presence of several putative secreted protein families in the cat flea salivary gland homogenates. Both transcriptomic and proteomic approaches confirmed that FS-H-like proteins and acid phosphatases lacking their putative catalytic residues are the two most abundant salivary proteins families of C. felis and are potentially related to blood acquisition. We also report several novel sequences similar to apyrases, odorant binding proteins, antigen 5, cholinesterases, proteases, and proteases inhibitors, in addition to putative novel sequences that presented low or no sequence identity to previously deposited sequences. Together, the data represents an extended reference for the identification and characterization of the pharmacological activity present in C. felis salivary glands.

Integrated analysis of the sialotranscriptome and sialoproteome of the rat flea Xenopsylla cheopis

Over the last 20 years, advances in sequencing technologies paired with biochemical and structural studies have shed light on the unique pharmacological arsenal produced by the salivary glands of hematophagous arthropods that can target host hemostasis and immune response, favoring blood acquisition and, in several cases, enhancing pathogen transmission. Here we provide a deeper insight into Xenopsylla cheopis salivary gland contents pairing transcriptomic and proteomic approaches. Sequencing of 99 pairs of salivary glands from adult female X. cheopis yielded a total of 7432 coding sequences functionally classified into 25 classes, of which the secreted protein class was the largest. The translated transcripts also served as a reference database for the proteomic study, which identified peptides from 610 different proteins. Both approaches revealed that the acid phosphatase family is the most abundant salivary protein group from X. cheopis. Additionally, we report here novel sequences similar to the FS-H family, apyrases, odorant and hormone-binding proteins, antigen 5-like proteins, adenosine deaminases, peptidase inhibitors from different subfamilies, proteins rich in Glu, Gly, and Pro residues, and several potential secreted proteins with unknown function. SIGNIFICANCE: The rat flea X. cheopis is the main vector of Yersinia pestis, the etiological agent of the bubonic plague responsible for three major pandemics that marked human history and remains a burden to human health. In addition to Y. pestis fleas can also transmit other medically relevant pathogens including Rickettsia spp. and Bartonella spp. The studies of salivary proteins from other hematophagous vectors highlighted the importance of such molecules for blood acquisition and pathogen transmission. However, despite the historical and clinical importance of X. cheopis little is known regarding their salivary gland contents and potential activities. Here we provide a comprehensive analysis of X. cheopis salivary composition using next generation sequencing methods paired with LC-MS/MS analysis, revealing its unique composition compared to the sialomes of other blood-feeding arthropods, and highlighting the different pathways taken during the evolution of salivary gland concoctions. In the absence of the X. cheopis genome sequence, this work serves as an extended reference for the identification of potential pharmacological proteins and peptides present in flea saliva.

Antimicrobial and Anti-inflammatory Effects of a Novel Peptide From the Skin of Frog Microhyla pulchra

Brevinins are an important antimicrobial peptide (AMP) family identified in the skin of Ranidae frogs and generally contain a characteristic ranabox structure at their C-terminal sequence. Herein a novel AMP named brevinin-2MP has been identified from the skin of the frog Microhyla pulchra by molecular cloning. Brevinin-2MP (GVITDTLKGVAKTVAAELLRKAHCKLTNSC) with a high amphipathic α-helix in sodium dodecyl sulfate solutions can destroy bacterial cell membrane and kill microbes. Furthermore, brevinin-2MP has been found to inhibit the lipopolysaccharide (LPS)-induced expression of pro-inflammatory NO, MCP-1, IL-6, and TNF-α via binding unidentified targets on the cell membrane and consequently suppressing the activation of MAPK/NF-κB signaling cascades induced by LPS in RAW 264.7 cells. Consistently, brevinin-2MP significantly alleviates the acute inflammatory response in carrageenan-induced mice paw. In conclusion, brevinin-2MP with anti-inflammatory and antimicrobial properties will be an ideal candidate drug molecule for bacterial inflammation treatment.

The toxin mimic FS48 from the salivary gland of Xenopsylla cheopis functions as a Kv1.3 channel-blocking immunomodulator of T cell activation

The Kv1.3 channel has been widely demonstrated to play crucial roles in the activation and proliferation of T cells, which suggests that selective blockers could serve as potential therapeutics for autoimmune diseases mediated by T cells. We previously described that the toxin mimic FS48 from salivary gland of Xenopsylla cheopis downregulates the secretion of proinflammatory factors by Raw 264.7 cells by blocking the Kv1.3 channel and the subsequent inactivation of the proinflammatory MAPK/NF-κB pathways. However, the effects of FS48 on human T cells and autoimmune diseases are unclear. Here, we described its immunomodulatory effects on human T cells derived from suppression of Kv1.3 channel. Kv1.3 currents in Jurkat T cells were recorded by whole-cell patch-clamp, and Ca2+ influx, cell proliferation, and TNF-α and IL-2 secretion were measured using Fluo-4, CCK-8, and ELISA assays, respectively. The in vivo immunosuppressive activity of FS48 was evaluated with a rat DTH model. We found that FS48 reduced Kv1.3 currents in Jurkat T cells in a concentration-dependent manner with an IC50 value of about 1.42 μM. FS48 also significantly suppressed Kv1.3 protein expression, Ca2+ influx, MAPK/NF-κB/NFATc1 pathway activation, and TNF-α and IL-2 production in activated Jurkat T cells. Finally, we show that FS48 relieved the DTH response in rats. We therefore conclude that FS48 can block the Kv1.3 channel and inhibit human T cell activation, which most likely contributes to its immunomodulatory actions and highlights the great potential of this evolutionary-guided peptide as a drug template in future studies.