The anti-microbial peptide TP359 attenuates inflammation in human lung cells infected with Pseudomonas aeruginosa via TLR5 and MAPK pathways

Fatty Acids Derived from Royal Jelly Exert Anti-Inflammatory and Antibacterial Activities in the Treatment of Pseudomonas aeruginosa-Induced Acute Pneumonia

Pseudomonas aeruginosa, an opportunistic pathogen, commonly causes hospital-acquired pneumonia. Royal jelly fatty acids (RJFAs), a mixture of various fatty acids extracted from royal jelly, exhibit antibacterial and anti-inflammatory properties in treating many infectious diseases. Nevertheless, the therapeutic mechanisms of RJFAs in treatment of acute P. aeruginosa pulmonary infection are still unclear. Herein, we initially extracted the fatty acids from royal jelly and characterized their chemical constituents using headspace gas chromatography-mass spectrometry. Furthermore, we examined the antibacterial effect of RJFAs in vitro and explored its therapeutic effect and molecular mechanisms in treating acute P. aeruginosa pulmonary infection in vivo. The in vitro antibacterial studies revealed that RJFAs significantly inhibited P. aeruginosa growth. Moreover, the in vivo studies showed that the RJFAs effectively mitigated the lung damage and inflammation induced by P. aeruginosa through impairing neutrophil infiltration, reducing the bacterial load in lung and diminishing the production of proinflammatory cytokines, including tumor necrosis factor (TNF-α), interleukin (IL-1β), IL-6, and macrophage inflammatory protein-2 (MIP-2). In addition, the mice treated with RJFAs exhibited reduced phosphorylation of extracellular signal-regulated kinase (ERK), p38, c-Jun N-terminal kinase (JNK), c-Jun, and nuclear factor-kappa B (NF-κB) p65 in the lung tissues in comparison with that of the mice without drug treatment. These findings demonstrated that RJFAs exhibited significant antibacterial and anti-inflammatory effects in treating the P. aeruginosa-induced acute pneumonia, and the anti-inflammatory effects were exerted through suppressing the mitogen-activated protein kinase/activator protein-1 (MAPK/AP-1) pathway and NF-κB activation, suggesting a promising therapeutic potential of RJFAs against acute bacterial pneumonia.

Antimicrobial Peptide Reduces Cytotoxicity and Inflammation in Canine Epidermal Keratinocyte Progenitor Cells Induced by Pseudomonas aeruginosa Infection

The direct effects and antimicrobial activity of synthetic antimicrobial peptides (AMPs) obtained from dogs, including cBD, cBD103, and cCath, against P. aeruginosa wild-type strain PAO1 and canine keratinocytes were analyzed. Antibacterial effects on planktonic bacteria were assessed by determining the minimum bactericidal concentrations (MBCs) of AMPs and by a time-kill assay. Antibiofilm effects were assessed using the microtiter plate assay. We also evaluated the effects of AMPs on cell cytotoxicity and host immune response induced by stimulating canine epidermal keratinocyte progenitor (CPEK) cells with PAO1 and its LPS. cBD, cBD103, and cCath all exhibited dose-dependent antimicrobial and antibiofilm effects. In particular, 25 μg/mL cBD103 showed rapid bactericidal activity within 60 min and inhibited biofilm formation. In addition, pretreatment with cBD103 (25 µg/mL) and cCath (50 µg/mL) 1 h before stimulation significantly reduced the cytotoxicity of the CPEK cells by PAO1 and LPS-induced IL-6 and TNF-a expressions. cBD had little effect on the response to PAO1 and LPS in the cells. These results indicate the therapeutic potential of AMPs in P. aeruginosa skin infections. However, further studies on the mechanism of action of AMPs in keratinocytes and clinical trials are needed.

P. aeruginosa type III and type VI secretion systems modulate early response gene expression in type II pneumocytes in vitro

BACKGROUND

Lung airway epithelial cells are part of innate immunity and the frontline of defense against bacterial infections. During infection, airway epithelial cells secrete proinflammatory mediators that participate in the recruitment of immune cells. Virulence factors expressed by bacterial pathogens can alter epithelial cell gene expression and modulate this response. Pseudomonas aeruginosa, a Gram-negative opportunistic pathogen, expresses numerous virulence factors to facilitate establishment of infection and evade the host immune response. This study focused on identifying the role of two major P. aeruginosa virulence factors, type III (T3SS) and type VI (T6SS) secretion systems, on the early transcriptome response of airway epithelial cells in vitro.

RESULTS

We performed RNA-seq analysis of the transcriptome response of type II pneumocytes during infection with P. aeruginosa in vitro. We observed that P. aeruginosa differentially upregulates immediate-early response genes and transcription factors that induce proinflammatory responses in type II pneumocytes. P. aeruginosa infection of type II pneumocytes was characterized by up-regulation of proinflammatory networks, including MAPK, TNF, and IL-17 signaling pathways. We also identified early response genes and proinflammatory signaling pathways whose expression change in response to infection with P. aeruginosa T3SS and T6SS mutants in type II pneumocytes. We determined that T3SS and T6SS modulate the expression of EGR1, FOS, and numerous genes that are involved in proinflammatory responses in epithelial cells during infection. T3SS and T6SS were associated with two distinct transcriptomic signatures related to the activation of transcription factors such as AP1, STAT1, and SP1, and the secretion of pro-inflammatory cytokines such as IL-6 and IL-8.

CONCLUSIONS

Taken together, transcriptomic analysis of epithelial cells indicates that the expression of immediate-early response genes quickly changes upon infection with P. aeruginosa and this response varies depending on bacterial viability and injectosomes. These data shed light on how P. aeruginosa modulates host epithelial transcriptome response during infection using T3SS and T6SS.

Pathogenesis of the Pseudomonas aeruginosa Biofilm: A Review

Pseudomonas aeruginosa is associated with several human infections, mainly related to healthcare services. In the hospital, it is associated with resistance to several antibiotics, which poses a great challenge to therapy. However, one of the biggest challenges in treating P. aeruginosa infections is that related to biofilms. The complex structure of the P. aeruginosa biofilm contributes an additional factor to the pathogenicity of this microorganism, leading to therapeutic failure, in addition to escape from the immune system, and generating chronic infections that are difficult to eradicate. In this review, we address several molecular aspects of the pathogenicity of P. aeruginosa biofilms.

Advances in the development of antimicrobial peptides and proteins for inhaled therapy

Antimicrobial peptides and proteins (APPs) are becoming increasingly important in targeting multidrug-resistant (MDR) bacteria. APPs is a rapidly emerging area with novel molecules being produced and further optimised to enhance antimicrobial efficacy, while overcoming issues associated with biologics such as potential toxicity and low bioavailability resulting from short half-life. Inhalation delivery of these agents can be an effective treatment of respiratory infections owing to the high local drug concentration in the lungs with lower exposure to systemic circulation hence reducing systemic toxicity. This review describes the recent studies on inhaled APPs, including in vitro and in vivo antimicrobial activities, toxicity assessments, and formulation strategies whenever available. The review also includes studies on combination of APPs with other antimicrobial agents to achieve enhanced synergistic antimicrobial effect. Since different APPs have different biological and chemical stabilities, a targeted formulation strategy should be considered for developing stable and inhalable antimicrobial peptides and proteins. These strategies include the use of sodium chloride to reduce electrostatic interaction between APP and extracellular DNA in sputum, the use of D-enantiomers or dendrimers to minimise protease-mediated degradation and or the use of prodrugs to reduce toxicity. Although great effort has been put towards optimising the biological functions of APPs, studies assessing biological stability in inhalable aerosols are scarce, particularly for novel molecules. As such, formulation and manufacture of inhalable liquid and powder formulations of APPs are underexplored, yet they are crucial areas of research for clinical translation.

The inhibitory mechanisms of losartan and vitamin D on amiodarone-induced lung inflammation in rats: Role of mitogen-activated protein kinases/activator protein-1

Amiodarone (AMD), an antiarrhythmic drug, is used cautiously due to its lung toxicity that is characterized by alveolar inflammation followed by fatal fibrosis. AMD induces lung inflammation via increasing the alveolar macrophages and disturbing the balance of T-helper-1 (Th1) and Th2 cells cytokines. In this study, the role of the mitogen-activated protein kinases (MAPKs)/activator protein-1 (AP-1) pathway in AMD-induced lung inflammation was evaluated. Also, the anti-inflammatory and antifibrotic effects of losartan and/or vitamin D were investigated following 7, 14, and 28 days of AMD administration. AMD resulted in lung injury, inflammatory infiltration, and increased pulmonary levels of inflammatory cytokines starting from Week 1 of exposure. A significant increase in serum levels of interleukin-4 along with a significant reduction of interferon-gamma, in addition to strong expression of CD68, were reported after 14 and 28 days of AMD administration reflecting Th1/Th2 cytokines imbalance and the accumulation of alveolar macrophages, respectively. The phosphorylation of MAPKs (ERK1/2, JNK, p38) and AP-1 was significantly enhanced starting from Week 1 of exposure. Marked expression of transforming growth factor beta-1 and massive deposition of collagen were detected after 28 days reflecting late fibrosis. All these abnormalities were significantly mitigated by vitamin D and its combination with losartan. Losartan alone has less prominent anti-inflammatory effects particularly after 28 days; however, it efficiently prevented late fibrosis. This study concludes that MAPKs/AP-1 pathway is involved in AMD-induced lung inflammation and that vitamin D and/or losartan could be used as a prophylactic agent to prevent AMD-induced lung toxicity.

Pseudomonas aeruginosa induces p38MAP kinase-dependent IL-6 and CXCL8 release from bronchial epithelial cells via a Syk kinase pathway

Pseudomonas aeruginosa (Pa) infection is a major cause of airway inflammation in immunocompromised and cystic fibrosis (CF) patients. Mitogen-activated protein (MAP) and tyrosine kinases are integral to inflammatory responses and are therefore potential targets for novel anti-inflammatory therapies. We have determined the involvement of specific kinases in Pa-induced inflammation. The effects of kinase inhibitors against p38MAPK, MEK 1/2, JNK 1/2, Syk or c-Src, a combination of a p38MAPK with Syk inhibitor, or a novel narrow spectrum kinase inhibitor (NSKI), were evaluated against the release of the proinflammatory cytokine/chemokine, IL-6 and CXCL8 from BEAS-2B and CFBE41o- epithelial cells by Pa. Effects of a Syk inhibitor against phosphorylation of the MAPKs were also evaluated. IL-6 and CXCL8 release by Pa were significantly inhibited by p38MAPK and Syk inhibitors (p<0.05). Phosphorylation of HSP27, but not ERK or JNK, was significantly inhibited by Syk kinase inhibition. A combination of p38MAPK and Syk inhibitors showed synergy against IL-6 and CXCL8 induction and an NSKI completely inhibited IL-6 and CXCL8 at low concentrations. Pa-induced inflammation is dependent on p38MAPK primarily, and Syk partially, which is upstream of p38MAPK. The NSKI suggests that inhibiting specific combinations of kinases is a potent potential therapy for Pa-induced inflammation.

The Role of Innate Immunity in Pulmonary Infections

Innate immunity forms a protective line of defense in the early stages of pulmonary infection. The primary cellular players of the innate immunity against respiratory infections are alveolar macrophages (AMs), dendritic cells (DCs), neutrophils, natural killer (NK) cells, and innate lymphoid cells (ILCs). They recognize conserved structures of microorganisms through membrane-bound and intracellular receptors to initiate appropriate responses. In this review, we focus on the prominent roles of innate immune cells and summarize transmembrane and cytosolic pattern recognition receptor (PRR) signaling recognition mechanisms during pulmonary microbial infections. Understanding the mechanisms of PRR signal recognition during pulmonary pathogen infections will help us to understand pulmonary immunopathology and lay a foundation for the development of effective therapies to treat and/or prevent pulmonary infections.

Antipseudomonal and Immunomodulatory Properties of Esc Peptides: Promising Features for Treatment of Chronic Infectious Diseases and Inflammation

Persistent infections, such as those provoked by the Gram-negative bacterium Pseudomonas aeruginosa in the lungs of cystic fibrosis (CF) patients, can induce inflammation with lung tissue damage and progressive alteration of respiratory function. Therefore, compounds having both antimicrobial and immunomodulatory activities are certainly of great advantage in fighting infectious diseases and chronic inflammation. We recently demonstrated the potent antipseudomonal efficacy of the antimicrobial peptide (AMP) Esc(1-21) and its diastereomer Esc(1-21)-1c, namely Esc peptides. Here, we confirmed this antimicrobial activity by reporting on the peptides’ ability to kill P. aeruginosa once internalized into alveolar epithelial cells. Furthermore, by means of enzyme-linked immunosorbent assay and Western blot analyses, we investigated the peptides’ ability to detoxify the bacterial lipopolysaccharide (LPS) by studying their effects on the secretion of the pro-inflammatory cytokine IL-6 as well as on the expression of cyclooxygenase-2 from macrophages activated by P. aeruginosa LPS. In addition, by a modified scratch assay we showed that both AMPs are able to stimulate the closure of a gap produced in alveolar epithelial cells when cell migration is inhibited by concentrations of Pseudomonas LPS that mimic lung infection conditions, suggesting a peptide-induced airway wound repair. Overall, these results have highlighted the two Esc peptides as valuable candidates for the development of new multifunctional therapeutics for treatment of chronic infectious disease and inflammation, as found in CF patients.

Understanding Pseudomonas aeruginosa-Host Interactions: The Ongoing Quest for an Efficacious Vaccine

Pseudomonas aeruginosa is a leading cause of chronic respiratory infections in people with cystic fibrosis (CF), bronchiectasis or chronic obstructive pulmonary disease (COPD), and acute infections in immunocompromised individuals. The adaptability of this opportunistic pathogen has hampered the development of antimicrobial therapies, and consequently, it remains a major threat to public health. Due to its antimicrobial resistance, vaccines represent an alternative strategy to tackle the pathogen, yet despite over 50 years of research on anti-Pseudomonas vaccines, no vaccine has been licensed. Nevertheless, there have been many advances in this field, including a better understanding of the host immune response and the biology of P. aeruginosa. Multiple antigens and adjuvants have been investigated with varying results. Although the most effective protective response remains to be established, it is clear that a polarised Th2 response is sub-optimal, and a mixed Th1/Th2 or Th1/Th17 response appears beneficial. This comprehensive review collates the current understanding of the complexities of P. aeruginosa-host interactions and its implication in vaccine design, with a view to understanding the current state of Pseudomonal vaccine development and the direction of future efforts. It highlights the importance of the incorporation of appropriate adjuvants to the protective antigen to yield optimal protection.

Thrombospondin-1 as a Potential Therapeutic Target: Multiple Roles in Cancers

Thrombospondin-1, an extracellular matrix protein, is the first identified natural angiogenesis inhibitor. Thrombospondin-1 participates in a great number of physiological and pathological processes, including cell-cell and cell-matrix interactions via a number of cell receptors, including CD36 and CD47, which plays a vital role in mediating inflammation and performs a promoting effect in pulmonary arterial vasculopathy and diabetes. Thrombospondin-1 consists of six domains, which combine with different molecules and participate in various functions in cancers, serving as a critical member in diverse pathways in cancers. Thrombospondin-1 works as a cancer promotor in some pathways but as a cancer suppressor in others, which makes it highly possible that its erroneous functioning might lead to opposite effects. Therefore, subdividing the roles of thrombospondin-1 and distinguishing them in cancers are necessary. Complex structure and multiple roles take disadvantage of the research and application of thrombospondin-1. Compared with the whole thrombospondin-1 protein, each thrombospondin- 1 active peptide performs an uncomplicated structure and, nevertheless, a specific role. In other words, various thrombospondin-1 active peptides may function differently. For instance, thrombospondin-1 could both promote and inhibit glioblastoma, which is significantly inhibited by the three type I repeats, a thrombospondin-1 active peptide but promoted by the fragment 167-569, a thrombospondin-1 active peptide consisting of the procollagen homology domain and the three type I repeats. Further studies of the functions of thrombospondin-1 active peptides and applying them reasonably are necessary. In addition to mediating cancerogenesis, thrombospondin-1 is also affected by cancer development, as reflected by its expression in plasma and the cancer tissue. Therefore, thrombospondin-1 may be a potential biomarker for pre-clinical and clinical application. This review summarizes findings on the multiple roles of thrombospondin-1 in cancer processes, with a focus on its use as a potential therapeutic target.

Quercetin negatively regulates IL-1β production in Pseudomonas aeruginosa-infected human macrophages through the inhibition of MAPK/NLRP3 inflammasome pathways

Pseudomonas aeruginosa remains a leading cause of nosocomial and serious life-threatening infections, and contributes to increased mortality in immunocompromised individuals. P. aeruginosa infection triggers host immune response and often provokes potent inflammatory mediators, which do not necessarily eradicate the causative pathogen. On the other hand, it causes severe airway damage and eventually decreased lung function. Such unfavorable outcomes of inflammatory injury have necessitated the development of novel effective agents that can combat with P. aeruginosa-mediated inflammation. Herein, we investigated the potential of quercetin in regulating P. aeruginosa-induced inflammation, with particular emphasized on the interleukin-1β (IL-1β). Our results showed that quercetin exerted the potent inhibitory activity against the production of IL-1β in macrophages infected by live P. aeruginosa PAO1, without exhibiting cytotoxicity. According to our settings, such the potent inhibitory activity of quercetin was clearly demonstrated through its ability to efficiently inhibit IL-1β during P. aeruginosa infection, pre- or even post-infection. In addition, quercetin strongly suppressed MAPK signaling pathway by inhibiting phosphorylation of the p38 MAPK and JNK2, and molecular docking study supported well with this observation. Moreover, quercetin reduced the NLRP3 expression and inhibited the P. aeruginosa-mediated cleavage of caspase-1 as well as mature IL-1β. These results thus indicated that quercetin inhibition of P. aeruginosa-induced IL-1β production is mediated by suppressing the initial priming step and by inhibiting the NLRP3 inflammasome activation. Taken together, our findings demonstrated the promising regulatory activity of quercetin against IL-1β production in P. aeruginosa-infected macrophages, and indicated that quercetin has the potential to be effective as a novel therapeutic agent for treatment of P. aeruginosa-induced inflammation.

Selective deletion of MyD88 signaling in α-SMA positive cells ameliorates experimental intestinal fibrosis via post-transcriptional regulation

Intestinal fibrosis leading to strictures remains a significant clinical problem in inflammatory bowel diseases (IBD). The role of bacterial components in activating intestinal mesenchymal cells and driving fibrogenesis is largely unexplored. Tamoxifen-inducible α-SMA promoter Cre mice crossed with floxed MyD88 mice were subjected to chronic dextran sodium sulfate colitis. MyD88 was deleted prior to or after induction of colitis. Human intestinal myofibroblasts (HIMF) were exposed to various bacterial components and assessed for fibronectin (FN) and collagen I (Col1) production. RNA sequencing was performed. Post-transcriptional regulation was assessed by polysome profiling assay. Selective deletion of MyD88 in α-SMA-positive cells prior to, but not after induction of, experimental colitis decreased the degree of intestinal fibrosis. HIMF selectively responded to flagellin with enhanced FN or Col1 protein production in a MyD88-dependent manner. RNA sequencing suggested minimal transcriptional changes induced by flagellin in HIMF. Polysome profiling revealed higher proportions of FN and Col1 mRNA in the actively translated fractions of flagellin exposed HIMF, which was mediated by eIF2 alpha and 4EBP1. In conclusion, selectivity of flagellin-induced ECM secretion in HIMF is post-transcriptionally regulated. The results may represent a novel and targetable link between the gut microbiota and intestinal fibrogenesis.

Pseudomonas aeruginosa Biofilms: Host Response and Clinical Implications in Lung Infections

Pseudomonas aeruginosa is a major health challenge that causes recalcitrant multidrug-resistant infections, especially in immunocompromised and hospitalized patients. P. aeruginosa is an important cause of nosocomial and ventilator-associated pneumonia characterized by high prevalence and fatality rates. P. aeruginosa also causes chronic lung infections in individuals with cystic fibrosis. Multidrug- and totally drug-resistant strains of P. aeruginosa are increasing threats that contribute to high mortality in these patients. The pathogenesis of many P. aeruginosa infections depends on its ability to form biofilms, structured bacterial communities that can coat mucosal surfaces or invasive devices. These biofilms make conditions more favorable for bacterial persistence, as embedded bacteria are inherently more difficult to eradicate than planktonic bacteria. The molecular mechanisms that underlie P. aeruginosa biofilm pathogenesis and the host response to P. aeruginosa biofilms remain to be fully defined. However, it is known that biofilms offer protection from the host immune response and are also extremely recalcitrant to antimicrobial therapy. Therefore, development of novel therapeutic strategies specifically aimed at biofilms is urgently needed. Here, we review the host response, key clinical implications of P. aeruginosa biofilms, and novel therapeutic approaches to treat biofilms relevant to lung infections. Greater understanding of P. aeruginosa biofilms will elucidate novel avenues to improve outcomes for P. aeruginosa pulmonary infections.

Pseudomonas aeruginosa infection stimulates mitogen-activated protein kinases signaling pathway in human megakaryocytes

Pseudomonas aeruginosa is a major cause of nosocomial infections and contributes to higher mortality in hospitalized individuals. Infection by P. aeruginosa triggers host immune response through activation of pathogen recognition receptors, which are present in innate cells. Several studies have reported the mechanism of P. aeruginosa induced innate immunity in multiple cell types. But so far there is no reports on response of megakaryocytes to P. aeruginosa infection. Hence, our aim was to investigate the precise role and signaling mechanism of megakaryocytes during P. aeruginosa infection. In this study, we used Mo7e cells as representatives of human megakaryocyte and found that P. aeruginosa infection induces cytotoxicity in these cells. We further demonstrated that P. aeruginosa infection modulates p38 and extracellular signal regulated kinase pathways in Mo7e cells. Protein expression profiling in P. aeruginosa lipopolysaccharide-treated Mo7e cells revealed upregulation of importin subunit β and downregulation of metabolic enzymes. Our results suggest that P. aeruginosa infection regulates mitogen-activated protein kinases signaling pathway and importin in Mo7e cells and that this is a potential mechanism for nuclear translocation of nuclear factor binding near the κ light-chain gene in B cells and c-Jun N-terminal kinases to induce cell cytotoxicity.

MicroRNA-217 relieved neuropathic pain through targeting toll-like receptor 5 expression

Neuropathic pain is the most common chronic pain that is caused by nerve injury or disease that influences the nervous system. Increasing evidence suggested that microRNAs (miRNAs) play a crucial role in neuropathic pain and neuroinflammation development. However, the functional role of miR-217 in the development of neuropathic pain remains unknown. In this study, we used rats to establish a neuropathic pain model and showed that the miR-217 expression level was upregulated in the spinal dorsal horn of bilateral sciatic nerve chronic constriction injury (bCCI). However, the expression of miR-217 was not changed in the anterior cingulated cortex (ACC), hippocampus, and dorsal root ganglion (DRG) of bCCI rats. Ectopic expression of miR-217 attenuated neuropathic pain and suppressed neuroinflammation expression in vivo. We identified toll-like receptor 5 (TLR5) as a direct target gene of miR-217 in the PC12 cell. In addition, we demonstrated that the expression level of TLR5 was upregulated in bCCI rats. Moreover, restoration of TLR5 rescued the inhibitory roles induced by miR-217 overexpression on neuropathic pain and neuroinflammation development. These data suggested that miR-217 played a pivotal role in the development of neuropathic pain partly through regulating TLR5 expression.

MiR-150 alleviates neuropathic pain via inhibiting toll-like receptor 5

MicroRNAs (miRNAs) are reported as vital participators in the pathophysiological course of neuropathic pain. However, the underlying mechanisms of the functional roles of miRNAs in neuropathic pain are largely unknown. This study was designed to explore the potential role of miR-150 in regulating the process of neuropathic pain in a rat model established by chronic sciatic nerve injury (CCI). Overexpression of miR-150 greatly alleviated neuropathic pain development and reduced inflammatory cytokine expression, including COX-2, interleukin IL-6, and tumor necrosis factor (TNF)-α in CCI rats. By bioinformatic analysis, 3'-untranslated region (UTR) of Toll-like receptor (TLR5) was predicted to be a target of miR-150. TLR5 commonly serves as an important regulator of inflammation. Overexpression of miR-150 significantly suppressed the expression of TLR5 in vitro and in vivo. Furthermore, upregulation of TLR5 decreased the miR-150 expression and downregulation of TLR5 increased miR-150, respectively. Overexpression of TLR5 significantly reversed the miR-150-induced suppressive effects on neuropathic pain. In conclusion, our current study indicates that miR-150 may inhibit neuropathic pain development of CCI rats through inhibiting TLR5-mediated neuroinflammation. Our findings suggest that miR-150 may provide a novel therapeutic target for neuropathic pain treatment.