Inhibition of CD40-induced N-Ras activation reduces leishmania major infection

Leishmania major MAPK4 intercepts and redirects CD40 signaling promoting infection

The parasite Leishmania resides as amastigotes within the macrophage parasitophorous vacuoles inflicting the disease Leishmaniasis. Leishmania selectively modulates mitogen-activated protein kinase (MAPK) phosphorylation subverting CD40-triggered anti-leishmanial functions of macrophages. The mechanism of any pathogen-derived molecule induced host MAPK modulation remains poorly understood. Herein, we show that of the fifteen MAPKs, LmjMAPK4 expression is higher in virulent L. major. LmjMAPK4- detected in parasitophorous vacuoles and cytoplasm- binds MEK-1/2, but not MKK-3/6. Lentivirally-overexpressed LmjMAPK4 augments CD40-activated MEK-1/2-ERK-1/2-MKP-1, but inhibits MKK3/6-p38MAPK-MKP-3, phosphorylation. A rationally-identified LmjMAPK4 inhibitor reinstates CD40-activated host-protective anti-leishmanial functions in L. major-infected susceptible BALB/c mice. These results identify LmjMAPK4 as a MAPK modulator at the host-pathogen interface and establish a pathogen-intercepted host receptor signaling as a scientific rationale for identifying drug targets.

Decoding the contextual duality of CD40 functions

Previously, we established that as a function of its mode of interaction with its ligand or cellular conditions such as membrane lipids, preexisting signaling intermediates activation status, a transmembrane receptor, as represented here with CD40, can induce counteractive cellular responses. Using CD40-binding peptides, recombinant mutated CD40-ligands, and an agonistic antibody, we have established the functional duality of CD40. CD40 builds up two constitutionally different signalosomes on lipid raft and non-raft membrane domains initiating two different signaling pathways. Although this initial signaling may be modified by the pre-existing signaling conditions downstream and may be subjected to feed-forward or negative signaling effects, the initial CD40-CD40L interaction plays a crucial role in the functional outcome of CD40. Herein, we have reviewed the influence of interaction between the CD40-CD40L evoking the functional duality of CD40 contingent upon different physiological states of the cells.

Genetic haplotypes associated with immune response to Leishmania infantum infection in dogs

Leishmaniasis is a zoonotic parasitic disease, and the main reservoir of the parasite is the dog, although recent years have seen an increase in other mammalian species. In the Mediterranean region, where it is an endemic disease, it is caused by the species Leishmania infantum. The Ibizan hound, an autochthonous breed of this region, appears to have a genetic resistance to parasitic infection, whereas other canine breeds, such as the Boxer, are susceptible to infection. These differences are related to the differentiated activation of the immune response, with the Ibizan hound activating the Th1 immune response, whereas the Boxer breed triggers the Th2 immune response. Cytokine levels and genomic haplotypes of several genes involved in the immune response were analysed in twenty-eight Ibizan hound (resistant canine breed model) and twenty-four Boxer (susceptible canine breed) without clinical signs in the Mediterranean region. Cytokine levels were analysed by ELISA commercial kits and haplotypes were studied using CanineHD DNA Analysis BeadChip including 165,480 mapped positions. The results show 126 haplotypes associated with differential immune response in dogs. Specifically, haplotypes in IL12RB1, IL6R, CIITA, THEMIS, NOXA1, HEY2, RAB38, SLC35D2, SLC28A3, RASEF and DAPK1 genes are associated with serum levels of IFN-γ, IL-2, IL-8, and IL-18. These results suggest that the resistance or susceptibility to Leishmania infantum infection could be a consequence of haplotypes in several genes related to immune response. Future studies are needed to elucidate the relationship of these haplotypes with immune response and gene expression regulation.

CD40 induces selective routing of Ras isoforms to subcellular compartments

Ras GTPases are central to cellular signaling and oncogenesis. The three loci of the Ras gene encode for four protein isoforms namely Harvey-Ras (H-Ras), Kirsten-Ras (K-Ras 4A and 4B), and Neuroblastoma-Ras (N-Ras) which share ~ 80% sequence similarity and used to be considered functionally redundant. The small molecule inhibitors of Ras lack specificity for the isoforms leading to widespread toxicity in Ras-targeted therapeutics. Ras isoforms' tissue-specific expression and selective association with carcinogenesis, embryonic development, and infection suggested their non-redundancy. We show that CD40, an antigen-presenting cell (APC)-expressed immune receptor, induces selective relocation of H-Ras, K-Ras, and N-Ras to the Plasma membrane (PM) lipid rafts, mitochondria, endoplasmic reticulum (ER), but not to the Golgi complex (GC). The two palmitoylated Ras isoforms-H-Ras and N-Ras-have a similar pattern of colocalization into the lipid-rich raft microdomain of the PM at early time points when compared to non-palmitoylated K-Ras (4B) with polylysine residues. CD40-induced trafficking of H-Ras and K-Ras to mitochondria and ER was found to be similar but different from that of N-Ras. Trafficking of all the Ras isoforms to the GC was independent of CD40 stimulation. The receptor-driven trafficking and spatial segregation of H-Ras, K-Ras, and N-Ras imply isoform-specific subcellular signaling platforms for the functional non-redundancy of Ras isoforms. PDB structures have been modified to illustrate various signaling proteins.

Immune and Genomic Analysis of Boxer Dog Breed and Its Relationship with Leishmania infantum Infection

Simple Summary

Leishmaniosis is a zoonotic disease, endemic in 88 countries, including those from the Mediterranean region. Several authors indicate differences in susceptibility and resistance to leishmaniosis in different canine breeds, with boxer being one of the breeds with a higher prevalence of the disease. This study analyzes the serum profiles of cytokines related to the immune response, together with the screening of genomic variants fixed in boxer breed samples, to understand their differential susceptibility to L. infantum infection. The results of this study indicate new pathways related to L. infantum infection and immune response in boxers, involving genes related to interleukin and toll-like receptors, as well as to the immune system and the regulation of expression. Future studies are required to elucidate the role of specific genes in the L. infantum infection mechanism in this canine breed.

Abstract

Leishmaniosis, one of the most important zoonoses in Europe, is caused by Leishmania infantum, an intracellular protozoan parasite. This disease is endemic in the Mediterranean area, where the main reservoir is the dog. Several studies indicate a possible susceptibility to L. infantum infection with clinical signs in some canine breeds. One of them is the boxer breed, which shows a high prevalence of disease. In this study, immunological and genomic characterization of serum samples from boxer dogs living in the Mediterranean area were evaluated to analyze the immune response and the possible genetic explanation for this susceptibility. Serum levels of cytokines IFN-γ, IL-2, IL-6, IL-8, and IL-18 were determined by ELISA commercial tests, while the genotyping study was performed using the CanineHD DNA Analysis BeadChip. The results show relevant differences in the serum levels of cytokines compared to published data on other canine breeds, as well as sequence changes that could explain the high susceptibility of the boxer breed to the disease. Concretely, polymorphic variants in the CIITA, HSF2BP, LTBP1, MITF, NOXA1, PKIB, RAB38, RASEF, TLE1, and TLR4 genes were found, which could explain the susceptibility of this breed to L. infantum infection.

Associations between interleukin-1-B gene -511G/A polymorphism and sepsis risk: A meta-analysis

The role of the cytokine (IL) gene has been indicated in the progression of sepsis. Nevertheless, the outcomes remain controversial. This meta-analysis aimed to examine the relationship of IL-1B gene -511G/A polymorphism and the risk of sepsis. To perform a retrospective database analysis, the CNKI PubMed,EMBASE and Cochrane Library databases were searched for related articles. Then, the combined odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were calculated using a fixed- or a random-effects model. A total of six related articles were discovered. The result of the meta-analysis showed that IL-1B -511G/A polymorphism was not significantly correlated with sepsis risk in the total population, but in the subgroup analysis we found that IL-1B -511G/A polymorphism was associated with sepsis risk in Caucasian populations (A vs. G: OR = 1.22, 95 %CI = 1.01-1.48; AA vs. GG: OR = 2.14, 95 %CI = 1.33-3.43; Recessive model: OR = 2.59, 95 %CI = 1.68-4.01). This meta-analysis showed that the IL-1B -511A allele might be a low-penetrant risk factor for sepsis in Caucasians.

G Protein-Coupled Receptors as Potential Intercellular Communication Mediators in Trypanosomatidae

Detection and transduction of environmental signals, constitute a prerequisite for successful parasite invasion; i.e., Leishmania transmission, survival, pathogenesis and disease manifestation and dissemination, with diverse molecules functioning as inter-cellular signaling ligands. Receptors [i.e., G protein-coupled receptors (GPCRs)] and their associated transduction mechanisms, well conserved through evolution, specialize in this function. However, canonical GPCR-related signal transduction systems have not been described in Leishmania, although orthologs, with reduced domains and function, have been identified in Trypanosomatidae. These inter-cellular communication means seem to be essential for multicellular and unicellular organism’s survival. GPCRs are flexible in their molecular architecture and may interact with the so-called receptor activity-modifying proteins (RAMPs), which modulate their function, changing GPCRs pharmacology, acting as chaperones and regulating signaling and/or trafficking in a receptor-dependent manner. In the skin, vasoactive- and neuro- peptides released in response to the noxious stimuli represented by the insect bite may trigger parasite physiological responses, for example, chemotaxis. For instance, in Leishmania (V.) braziliensis, sensory [Substance P, SP, chemoattractant] and autonomic [Vasoactive Intestinal Peptide, VIP, and Neuropeptide Y, NPY, chemorepellent] neuropeptides at physiological levels stimulate in vitro effects on parasite taxis. VIP and NPY chemotactic effects are impaired by their corresponding receptor antagonists, suggesting that the stimulated responses might be mediated by putative GPCRs (with essential conserved receptor domains); the effect of SP is blocked by [(D-Pro 2, D-Trp7,9]-Substance P (10^-6 M)] suggesting that it might be mediated by neurokinin-1 transmembrane receptors. Additionally, vasoactive molecules like Calcitonin Gene-Related Peptide [CGRP] and Adrenomedullin [AM], exert a chemorepellent effect and increase the expression of a 24 kDa band recognized in western blot analysis by (human-)-RAMP-2 antibodies. In-silico search oriented towards GPCRs-like receptors and signaling cascades detected a RAMP-2-aligned sequence corresponding to Leishmania folylpolyglutamate synthase and a RAMP-3 aligned protein, a hypothetical Leishmania protein with yet unknown function, suggesting that in Leishmania, CGRP and AM activities may be modulated by RAMP- (-2) and (-3) homologs. The possible presence of proteins and molecules potentially involved in GPCRs cascades, i.e., RAMPs, signpost conservation of ancient signaling systems associated with responses, fundamental for cell survival, (i.e., taxis and migration) and may constitute an open field for description of pharmacophores against Leishmania parasites.

Ras Isoforms from Lab Benches to Lives-What Are We Missing and How Far Are We?

The central protein in the oncogenic circuitry is the Ras GTPase that has been under intense scrutiny for the last four decades. From its discovery as a viral oncogene and its non-oncogenic contribution to crucial cellular functioning, an elaborate genetic, structural, and functional map of Ras is being created for its therapeutic targeting. Despite decades of research, there still exist lacunae in our understanding of Ras. The complexity of the Ras functioning is further exemplified by the fact that the three canonical Ras genes encode for four protein isoforms (H-Ras, K-Ras4A, K-Ras4B, and N-Ras). Contrary to the initial assessment that the H-, K-, and N-Ras isoforms are functionally similar, emerging data are uncovering crucial differences between them. These Ras isoforms exhibit not only cell-type and context-dependent functions but also activator and effector specificities on activation by the same receptor. Preferential localization of H-, K-, and N-Ras in different microdomains of the plasma membrane and cellular organelles like Golgi, endoplasmic reticulum, mitochondria, and endosome adds a new dimension to isoform-specific signaling and diverse functions. Herein, we review isoform-specific properties of Ras GTPase and highlight the importance of considering these towards generating effective isoform-specific therapies in the future.

Unraveling the Role of Immune Checkpoints in Leishmaniasis

Leishmaniasis are Neglected Tropical Diseases affecting millions of people every year in at least 98 countries and is one of the major unsolved world health issues. Leishmania is a parasitic protozoa which are transmitted by infected sandflies and in the host they mainly infect macrophages. Immunity elicited against those parasites is complex and immune checkpoints play a key role regulating its function. T cell receptors and their respective ligands, such as PD-1, CTLA-4, CD200, CD40, OX40, HVEM, LIGHT, 2B4 and TIM-3 have been characterized for their role in regulating adaptive immunity against different pathogens. However, the exact role those receptors perform during Leishmania infections remains to be better determined. This article addresses the key role immune checkpoints play during Leishmania infections, the limiting factors and translational implications.

Potential therapeutic targets shared between leishmaniasis and cancer

The association of leishmaniasis and malignancies in human and animal models has been highlighted in recent years. The misdiagnosis of coexistence of leishmaniasis and cancer and the use of common drugs in the treatment of such diseases prompt us to further survey the molecular biology of Leishmania parasites and cancer cells. The information regarding common expressed proteins, as possible therapeutic targets, in Leishmania parasites and cancer cells is scarce. Therefore, the current study reviews proteins, and investigates the regulation and functions of several key proteins in Leishmania parasites and cancer cells. The up- and down-regulations of such proteins were mostly related to survival, development, pathogenicity, metabolic pathways and vital signalling in Leishmania parasites and cancer cells. The presence of common expressed proteins in Leishmania parasites and cancer cells reveals valuable information regarding the possible shared mechanisms of pathogenicity and opportunities for therapeutic targeting in leishmaniasis and cancers in the future.

Development and Characterization of an Avirulent Leishmania major Strain

Leishmania major causes cutaneous leishmaniasis. An antileishmanial vaccine for humans is unavailable. In this study, we report development of two attenuated L. major strains-5ASKH-HP and LV39-HP-by continuous culture (high passage) of the corresponding virulent strains (low passage). Both avirulent strains showed similar changes in proteome profiles when analyzed by surface-enhanced laser desorption ionization mass spectrometry. Liquid chromatography-mass spectrometry and microarray characterization of 5ASKH strains revealed substantially altered gene and protein expression profiles, respectively. Both virulent and avirulent L. major strains grew comparably in culture, but the avirulent strain survived significantly less in BALB/c-derived peritoneal macrophages. Both attenuated strains failed to infect BALB/c mice and elicited IFN-γ, but not IL-4 and IL-10, responses. 5ASKH-HP parasites failed to induce significant infection even in severely immunocompromised- SCID or inducible NO synthase-, CD40-, or IL-12-deficient mice, indicating attenuation. The avirulent strain induced less IL-10, but higher IL-12, in macrophages. The avirulent strain failed to reduce CD40 relocation to the detergent-resistant membrane domain and to inhibit CD40-induced phosphorylation of the kinases Lyn and protein kinase C-β and MAPKs MKK-3/6 and p38MAPK or to upregulate MEK-1/2 and ERK-1/2 in BALB/c-derived peritoneal macrophages. The virulent and the avirulent strains reciprocally modulated CD40-induced Ras-mediated signaling through PI-3K and Raf-1. Avirulent 5ASKH-primed BALB/c mice were protected against virulent L. major challenge infection. The loss of virulence accompanied by substantially altered proteome profiles and the elicitation of host-protective immune responses indicate plausibly irreversible attenuation of the L. major strain and its potential use as a vaccine strain.

Ras isoforms: signaling specificities in CD40 pathway

Background

Ras are small cellular GTPases which regulate diverse cellular processes. It has three isoforms: H-Ras, K-Ras, and N-Ras. Owing to the N-terminus (1–165 residues) sequence homology these isoforms were thought to be functionally redundant. However, only K-Ras-deficient mice but not H-Ras- and N-Ras-deficient mice show embryonic lethality. Similarly, mutations in a given Ras isoform are associated with a particular type of cancer. Moreover, we have previously reported that Ras isoforms perform unique functions in Leishmania major infection. Thus, Ras isoforms are implicated to have signaling and functional specificity but the mechanism remains to be elucidated.

Result

Using CD40 as a model receptor, we showed that depending on the strength of signaling, specific Ras isoforms are activated. Weak CD40 signal activates N-Ras, whereas strong signal activates H-Ras and K-Ras. Additionally, we showed that suppression of N-Ras expression reduced CD40-induced extracellular signal–regulated kinase-1/2 (ERK-1/2) activation and Interleukin (IL)-10 production; whereas suppression of H-Ras or K-Ras reduced CD40-induced p38 mitogen-activated protein kinase (p38MAPK) activation and IL-12 production. Furthermore, we showed that Ras isoforms have activator (GEF) specificity as weak CD40 signal-activated N-Ras requires Sos-1/2 whereas strong CD40 signal-activated H-Ras/K-Ras requires Ras-GRP as the guanine-nucleotide exchange factor (GEF) inducing ERK-1/2- or p38MAPK-mediated IL-10 or IL-12 productions, respectively, in macrophages. Silencing of syk reduced CD40-induced N-Ras activation but silencing of lyn inhibited H-Ras and K-Ras activation. In CD40 signaling, Ras isoforms also showed effector specificity; while H-Ras and K-Ras showed specificity for phosphatidyl inositol-3 kinase activation at high dose of CD40 stimulation, N-Ras primarily associated with Raf-1 at low dose of CD40 stimulation. Moreover, fractal analysis showed that functional site surface roughness for H-Ras (SurfaceFD = 2.39) and K-Ras (SurfaceFD = 2.39) are similar but significantly different from N-Ras (SurfaceFD = 2.25).

Conclusion

The activator and effector specificities of Ras isoforms in CD40 signaling indicated their differential involvement in CD40 pathway and in maintaining the reciprocity. Our observations reveal Ras-regulated signaling outcome and its potential for developing Ras isoform-targeted immunotherapy and prophylaxis.

Graphical abstract

Ras isoforms selectively regulate antigen-specific immune response

H-/K-Ras and N-Ras isoforms were proposed to lack functional specificities due to similarity in 1-165 amino acids. As recent studies implied Ras isoform-specific developmental effects, we examined their functional specificity using Leishmania major infection, anti-hapten antibody response and carrier-specific T cell response. While N-Ras overexpression increased L. major infection in resistant C57BL/6 mice, H-Ras or K-Ras overexpression reduced the infection in susceptible BALB/c mice. These Ras isoforms differentially regulated anti-TNP antibody response in TNP-Ova-primed, but not in TNP-Ficoll- or TNP-LPS-primed, BALB/c mice. Ras isoform-specific silencing selectively modulated Ova-specific T cell response. The data indicate Ras isoform-specific regulation of antigen-specific immune response.

Leishmania species-dependent functional duality of toll-like receptor 2

Toll-like receptors (TLRs) are a subset of pattern recognition receptors (PRR) in innate immunity and act as a connecting link between innate and adaptive immune systems. During Leishmania infection, the activation of TLRs influences the pathogen-specific immune responses, which may play a decisive role in determining the outcome of infection, toward elimination or survival of the pathogen. Antigen-presenting cells (APCs) of the innate immune system such as macrophages, dendritic cells (DCs), neutrophils, natural killer (NK) cells, and NKT cells express TLR2, which plays a crucial role in the parasite recognition and elicitation of immune responses in Leishmania infection. Depending on the infecting Leishmania species, the TLR2 pathways may result in a host-protective or a disease-exacerbating response. While Leishmania major and Leishmania donovani infections trigger TLR2-related host-protective and non-protective immune responses, Leishmania mexicana and Leishmania infantum infections are reported to elicit TLR2-mediated host-protective responses and Leishmania amazonensis and Leishmania braziliensis infections are reported to evoke a disease-exacerbating response. These findings illustrate that TLR2-related effector functions are diverse and may be exerted in a species- or strain-dependent manner. TLR2 agonists or antagonists may have therapeutic potentials to trigger the desired immune response during leishmaniasis. In this review, we discuss the TLR2-related immune responses during leishmaniasis and highlight the novel insights into the possible role of TLR2-driven resistance or susceptibility to Leishmania.

Druggable Targets in Cyclic Nucleotide Signaling Pathways in Apicomplexan Parasites and Kinetoplastids against Disabling Protozoan Diseases in Humans

Cell signaling in eukaryotes is an evolutionarily conserved mechanism to respond and adapt to various environmental changes. In general, signal sensation is mediated by a receptor which transfers the signal to a cascade of effector proteins. The cyclic nucleotides 3′,5′-cyclic adenosine monophosphate (cAMP) and 3′,5′-cyclic guanosine monophosphate (cGMP) are intracellular messengers mediating an extracellular stimulus to cyclic nucleotide-dependent kinases driving a change in cell function. In apicomplexan parasites and kinetoplastids, which are responsible for a variety of neglected, tropical diseases, unique mechanisms of cyclic nucleotide signaling are currently identified. Collectively, cyclic nucleotides seem to be essential for parasitic proliferation and differentiation. However, there is no a genomic evidence for canonical G-proteins in these parasites while small GTPases and secondary effector proteins with structural differences to host orthologues occur. Database entries encoding G-protein-coupled receptors (GPCRs) are still without functional proof. Instead, signals from the parasite trigger GPCR-mediated signaling in the host during parasite invasion and egress. The role of cyclic nucleotide signaling in the absence of G-proteins and GPCRs, with a particular focus on small GTPases in pathogenesis, is reviewed here. Due to the absence of G-proteins, apicomplexan parasites and kinetoplastids may use small GTPases or their secondary effector proteins and host canonical G-proteins during infection. Thus, the feasibility of targeting cyclic nucleotide signaling pathways in these parasites, will be an enormous challenge for the identification of selective, pharmacological inhibitors since canonical host proteins also contribute to pathogenesis.

Free radical stress induces DNA damage response in RAW264.7 macrophages during Mycobacterium smegmatis infection

Genomic instability resulting from oxidative stress responses may be traced to chromosomal aberration. Oxidative stress suggests an imbalance between the systemic manifestation of reactive free radicals and biological system's ability to repair resulting DNA damage and chromosomal aberration. Bacterial infection associated insult is considered as one of the major factors leading to such stress conditions. To study free radical responses by host cells, RAW 264.7 macrophages were infected with non-pathogenic M. smegmatis mc²155 at different time points. The infection process was followed up with an assessment of free radical stress, cytokine, toll-like receptors (TLRs) and the resulting DNA damage profiles. Results of CFU count showed that maximum infection in macrophages was achieved after 9 h of infection. Host responses to the infection across different time periods were validated from nitric oxide quantification and expression of iNOS and were plotted at regular intervals. IL-10 and TNF-α expression profile at protein and mRNA level showed a heightened pro-inflammatory response by host macrophages to combat M. smegmatis infection. The expression of TLR4, a receptor for recognition of mycobacteria, in infected macrophages reached the highest level at 9 h of infection. Furthermore, comet tail length, micronuclei and γ-H2AX foci recorded the highest level at 9 h of infection, pointing to the fact that breakage in DNA double strands in macrophage reaches its peak at 9 h of infection. In contrast, treatment with ROS inhibitor N-acetyl-L-cysteine (NAC) prevented host cell death through reduction in oxidative stress and DNA damage response during M. smegmatis infection. Therefore, it can be concluded that enhanced oxidative stress response in M. smegmatis infected macrophages might be correlated with DNA damage response.

Leishmania donovani infection differentially regulates small G-proteins

Leishmania is a protozoan parasite that resides and replicates in macrophages and causes leishmaniasis. The parasite alters the signaling cascade in host macrophages and evades the host machinery. Small G-proteins are GTPases, grouped in 5 different families that play a crucial role in the regulation of cell proliferation, cell survival, apoptosis, intracellular trafficking, and transport. In particular, the Ras family of small G-proteins has been identified to play a significant role in the cellular functions mentioned before. Here, we studied the differential expression of the most important small G-proteins during Leishmania infection. We found major changes in the expression of different isoforms of Ras, mainly in N-Ras. We observed that Leishmania donovani infection led to enhanced N-Ras expression, whereas it inhibited K-Ras and H-Ras expression. Furthermore, an active N-Ras pull-down assay showed enhanced N-Ras activity. L donovani infection also increased extracellular signal-regulated kinase 1/2 phosphorylation and simultaneously decreased p38 phosphorylation. In contrast, pharmacological inhibition of Ras led to reduction in the phosphorylation of extracellular signal-regulated kinase 1/2 and enhanced the phosphorylation of p38 in Leishmania-infected cells, which could lead to increased interleukin-12 expression and decreased interleukin-10 expression. Indeed, farnesylthiosalicyclic acid (a Ras inhibitor), when used at the effective level in L donovani-infected macrophages, reduced amastigotes in the host macrophages. Thus, upregulated N-Ras expression during L donovani infection could be a novel immune evasion strategy of Leishmania and would be a potential target for antileishmanial immunotherapy.

Pretreatment with bacterial components promotes DSS-injured colonic epithelial repair through the activation of STAT-3

Bacterial protection and epithelial repair are important against inflammatory bowel disease (IBD). The present study was designed to examine the effects of different bacterial components on the repair of normal and dextran sodium sulfate (DSS)‑treated colonic epithelial cells and the corresponding mechanisms. Human colonic epithelial cells (HT‑29) were pretreated with various doses of LPS or CpG‑dsDNA for 24 h and then treated with or without DSS for another 24 h. The epithelial repair was assessed by video analyses following mechanical injury. The epithelial expression of cluster of differentiation (CD)40 was assayed using flow cytometeric analysis. The production of interleukin (IL)‑6 and tumor necrosis factor (TNF) in the cell culture medium were measured using ELISA. The expression of p38 mitogen‑activated protein kinase (MAPK) and signal transducer and activator of transcription (STAT)‑3 were examined using western blot analysis and reverse transcription‑quantitative polymerase chain reaction analysis. MAPK and STAT‑3 inhibitors were also administrated to observe signaling‑mediated repair. The results showed that pretreatment with lipopolysaccharide (LPS) or CpG‑dsDNA promoted epithelial repair of the DSS‑treated cells. The promoting effects were associated with the downregulation of CD40 molecules, inhibition of the p38 MAPK/TNFα pathway and activation of the STAT3/IL‑6 pathway. The STAT3 inhibitor abrogated the protective effects of LPS and CpG‑dsDNA on wound repair. These results demonstrated that LPS and CpG‑dsDNA induced preadaptation to DSS injury. This preadaptation was accompanied by the activation of STAT‑3. Thus, bacterial components may be used as a strategy for the therapeutic prevention of IBD.

The Role of Signaling via Aqueous Pore Formation in Resistance Responses to Amphotericin B

Drug resistance studies have played an important role in the validation of antibiotic targets. In the case of the polyene antibiotic amphotericin B (AmB), such studies have demonstrated the essential role that depletion of ergosterol plays in the development of AmB-resistant (AmB-R) organisms. However, AmB-R strains also occur in fungi and parasitic protozoa that maintain a normal level of ergosterol at the plasma membrane. Here, I review evidence that shows not only that there is increased protection against the deleterious consequences of AmB-induced ion leakage across the membrane in these resistant pathogens but also that a set of events are activated that block the cell signaling responses that trigger the oxidative damage produced by the antibiotic. Such signaling events appear to be the consequence of a membrane-thinning effect that is exerted upon lipid-anchored Ras proteins by the aqueous pores formed by AmB. A similar membrane disturbance effect may also explain the activity of AmB on mammalian cells containing Toll-like receptors. These resistance mechanisms expand our current understanding of the role that the formation of AmB aqueous pores plays in triggering signal transduction responses in both pathogens and host immune cells.