Mouse Peritonitis Model Research Articles

Near-Infrared Fluorescence Probe for Visualizing Fluctuations of Peroxynitrite in Living Cells and Inflammatory Mouse Models

Inflammation is a vital protective response in living systems and closely related to various diseases. As a member of the reactive oxygen species (ROS) family, peroxynitrite (ONOO−) is involved in the organism’s inflammatory process and considered as an important biomarker of inflammation. Therefore, the construction of a simple, rapid, and sensitive tool for detecting ONOO− is of great importance for the diagnosis of inflammation. In this study, we constructed the new near-infrared fluorescence probe BDP-ENE-S-Py+ based on BODIPY dye, which has the advantages of fast response speed (2 min), good selectivity, and a high signal-to-noise ratio. Moreover, the probe had a good linear relationship (LOD = 120 nM) when the ONOO− concentration was 10–35 µM. In addition, BDP-ENE-S-Py+ could detect exogenous ONOO− in liver cancer cells without interference from other reactive oxygen species and visualize the fluctuations in ONOO− concentrations in cells. More importantly, BDP-ENE-S-Py+ was able to track the upregulation of ONOO− content in a mouse model of peritonitis induced by LPS. This work demonstrated that the near-infrared fluorescent probe for visualizing ONOO− level fluctuations could provide a promising tool for inflammation-related studies.

149 Chronic Immunotoxicity of Multi-Walled Carbon Nanotubes on Macrophages via MMP-12

Abstract Background The toxicological effects of nanomaterials, such as multi-walled carbon nanotubes (MWCNTs), on the immune system are considerably understood. However, the precise relationship between long-term exposure to MWCNTs and chronic inflammation remains unclear. Methods and Finding In this study, exposure to Taquann-treated MWCNTs (T-CNTs) was performed using aerosols generated in an inhalation chamber. At 12 months after T-CNT exposure, alveolar inflammation with macrophage accumulation and hypertrophy of the alveolar walls were observed. The fibrotic lesions were enhanced by T-CNT exposure. The cell surface phenotype of macrophages in the bronchoalveolar lavage fluid was shifted to the M1 macrophage phenotype. In addition, the alveolar macrophages of T-CNT-exposed mice produced matrix metalloprotinase-12 (MMP-12). By contrast, a mouse model of chronic peritonitis was also established using intraperitoneal injection of T-CNTs with high dispersion efficiency. Chronic peritonitis with fibrosis was observed in T-CNT-injected mice, but not in Taquann-treated TiO2-injected mice. In vivo and in vitro experiments showed that MMP-12 of macrophages was upregulated by T-CNT to enhance fibroblast activation and profibrotic molecule expression in fibroblasts. In addition, T-CNT-induced peritonitis reduced MMP-12 expression in Nfκb1−/− mice, suggesting that MMP-12-producing macrophages play a key role in chronic inflammation due to T-CNT exposure though NF-κB activation. Conclusion These results using the two models suggest that T-MWCNT exposure promoted chronic inflammation and fibrotic lesion formation in profibrotic macrophages via MMP12 for prolonged periods. The results of this study could be helpful in understanding the molecular toxicity of nanomaterial and chronic inflammation.

ELMO1 Deficiency Reduces Neutrophil Chemotaxis in Murine Peritonitis.

Peritoneal inflammation remains a major cause of treatment failure in patients with kidney failure who receive peritoneal dialysis. Peritoneal inflammation is characterized by an increase in neutrophil infiltration. However, the molecular mechanisms that control neutrophil recruitment in peritonitis are not fully understood. ELMO and DOCK proteins form complexes which function as guanine nucleotide exchange factors to activate the small GTPase Rac to regulate F-actin dynamics during chemotaxis. In the current study, we found that deletion of the Elmo1 gene causes defects in chemotaxis and the adhesion of neutrophils. ELMO1 plays a role in the fMLP-induced activation of Rac1 in parallel with the PI3K and mTORC2 signaling pathways. Importantly, we also reveal that peritoneal inflammation is alleviated in Elmo1 knockout mice in the mouse model of thioglycollate-induced peritonitis. Our results suggest that ELMO1 functions as an evolutionarily conserved regulator for the activation of Rac to control the chemotaxis of neutrophils both in vitro and in vivo. Our results suggest that the targeted inhibition of ELMO1 may pave the way for the design of novel anti-inflammatory therapies for peritonitis.

Green Biosynthesis of Silver Nanoparticles Using Aqueous Extracts of Ageratum Conyzoides and Their Anti-Inflammatory Effects.

The NLRP3 inflammasome, which plays a central role in innate immunity, is linked to a variety of inflammatory diseases, and thus it may provide a new target for the treatment of those diseases. Biosynthesized silver nanoparticles (AgNPs), particularly those synthesized using medicinal plant extracts, have recently been shown to be a promising therapeutic option. Herein, the aqueous extract of Ageratum conyzoids was used to prepare a series of sized AgNPs (AC-AgNPs), in which the smallest mean particle size was 30 ± 1.3 nm with a polydispersity of 0.328 ± 0.009. The ζ potential value was -28.77 with a mobility of -1.95 ± 0.24 cm2/(v·s). Its main ingredient, elemental silver, accounted for about 32.71 ± 4.87% of its mass, and other ingredients included amentoflavone-7,7⁗-dimethyl ether, 1,3,5-tricaffeoylquinic acid, kaempferol 3,7,4'-triglucoside, 5,6,7,3',4',5'-hexamethoxyflavone, kaempferol, and ageconyflavone B. In LPS+ATP-stimulated RAW 264.7 and THP-1 cells, AC-AgNPs significantly inhibited the release of IL-1β, IL-18, TNF-α, and caspase-1, indicating that AC-AgNPs can inhibit the activation of the NLRP3 inflammasome. The mechanistic study revealed that AC-AgNPs could decrease the phosphorylation levels of IκB-α and p65, resulting in decreased expression of NLRP3 inflammasome-related proteins, including pro-IL-1β, IL-1β, procaspase 1, caspase 1P20, NLRP3, and ASC, and also scavenge the level of intracellular ROS to prevent NLRP3 inflammasome assembly. Furthermore, AC-AgNPs attenuated the in vivo expression of inflammatory cytokines by suppressing NLRP3 inflammasome activation in a peritonitis mouse model. Our study provides evidence that the as-prepared AC-AgNPs can inhibit the inflammatory process by suppressing NLRP3 inflammasome activation and might be used to treat NLRP3 inflammasome-driven inflammatory diseases.

Impact of peritoneal lavage temperature during laparotomy in a preterm peritonitis mouse model using cecal slurry

BackgroundPeritoneal lavage (PL) during laparotomy is a treatment option for preterm bacterial peritonitis; however, its efficacy remains controversial. We investigated the effects of PL temperature during laparotomy on survival in a cecal slurry (CS)-induced preterm peritonitis mouse model. MethodsFour-day-old pups that were intraperitoneally administered 1.8 mg/g CS solution underwent laparotomy through a 5-mm transverse incision 2 h after CS injection (sham group). An additional PL was established during laparotomy with 500 µl of 25°C, 35°C, and 45°C sterile saline, respectively (PL25, PL35, and PL45 groups). Postoperative 7-day survival, body temperature, and plasma and ascites cytokine concentrations were evaluated for each group. ResultsPostoperative 7-day survival rates in the sham, PL25, PL35, and PL45 groups were 52.9%, 56.3%, 33.3%, and 18.2% (p=0.097), respectively. Median BT changes between before and after surgery were −1.85°C, −2.30°C, −3.40°C, and −1.80°C for each group (p=0.0065). The median ascites MCP-1 and IL-6 concentrations (pg/ml) at postoperative 2 h were 32,432, 16,244, 6279, and 5100 (p=0.049) and 22,346, 11,537, 5519, and 4535 (p=0.076), and plasma MCP-1 and IL-6 concentrations (pg/ml) were 68,687, 16,327, 9277, and 1868 (p=0.084) and 112,290, 14,415, 11,403, and 4113 (p=0.123) for each group, respectively. ConclusionPostoperative 7-day survivals were slightly improved by PL with 25°C sterile saline, however decreased by increasing PL temperatures to 35°C and 45°C in a CS-induced preterm peritonitis mouse model. As PL temperature was increased, both plasma and ascites MCP-1 and IL-6 concentrations tended to be suppressed, suggesting to decrease postoperative survivals.

Mast cells contribute to the resolution of allergic inflammation by releasing resolvin D1

BackgroundMast cells are initiators and main effectors of allergic inflammation, together with eosinophils, with whom they can interact in a physical and soluble cross-talk with marked pro-inflammatory features, the Allergic Effector Unit. The pro-resolution role of mast cells, alone or in co-culture with eosinophils, has not been characterized yet. ObjectivesWe aimed to investigate select pro-resolution pathways in mast cells in vitro and in vivo in allergic inflammation. MethodsIn vitro, we employed human and murine mast cells and analyzed release of resolvin D1 and expression of 15-lipoxygenase after IgE-mediated activation. We performed co-culture of IgE-activated mast cells with peripheral blood eosinophils and investigated 15-lipoxygenase expression and Resolvin D1 release. In vivo, we performed Ovalbumin/Alum and Ovalbumin/S. aureus enterotoxin B allergic peritonitis model in Wild Type mice following a MC “overshoot” protocol. ResultsWe found that IgE-activated mast cells release significant amounts of resolvin D1 30 min after activation, while 15-lipoxygenase expression remained unchanged. Resolvin D1 release was found to be decreased in IgE-activated mast cells co-cultured with peripheral blood eosinophils for 30 min In vivo, mast cell-overshoot mice exhibited a trend of reduced inflammation, together with increased peritoneal resolvin D1 release. ConclusionsMast cells can actively contribute to resolution of allergic inflammation by releasing resolvin D1.

TRPV1 is involved in abdominal hyperalgesia in a mouse model of lipopolysaccharide-induced peritonitis and influences the immune response via peripheral noradrenergic neurons

AimsThe transient receptor potential vanilloid subfamily 1 (TRPV1) not only plays a role as a nociceptor but also has some regulatory effects on the immune system. We investigated the effects of TRPV1 on abdominal pain and the immune system in lipopolysaccharide (LPS)-induced peritonitis and the association between TRPV1 and peripheral noradrenergic neurons. Main methodsExperiments were performed in 8- to 14-week-old male wild-type (WT) and TRPV1 knockout (KO) mice. The mice were intraperitoneally injected with a non-lethal dose of LPS. Pain assessment and investigation of changes in the immune system were performed. Denervation of sympathetic nerves and the noradrenergic splenic nerve was induced by intraperitoneal administration of 6-hydroxydopamine. Key findingsThe levels of serum cytokines were not significantly different in WT mice and TRPV1 KO mice. Abdominal mechanical hyperalgesia was greater in WT mice than in TRPV1 KO mice from 6 h to 3 days. The numbers of macrophages, neutrophils, dendritic cells, and CD4 T cells in the spleens of TRPV1 KO mice were significantly increased compared to those in WT mice 4 days after LPS administration. By noradrenergic denervation, the numbers of those cells in WT mice increased to levels comparable to those in TRPV1 KO mice. SignificanceIn LPS-induced peritonitis, abdominal inflammatory pain was transmitted via TRPV1. In addition, TRPV1 had an anti-inflammatory effect on the spleen in the late phase of peritonitis. This anti-inflammatory effect was thought to be mediated by activation of the sympathetic nervous system and/or noradrenergic splenic nerve induced by TRPV1 activation.

Tetrahedral Framework Nucleic Acids: A Novel Strategy for Antibiotic Treating Drug-Resistant Infections.

Antibiotic multiresistance (AMR) has emerged as a major threat to human health as millions of people die from AMR-related problems every year. As has been witnessed during the global COVID-19 pandemic, the significantly increased demand for antibiotics has aggravated the issue of AMR. Therefore, there is an urgent need to find ways to alleviate it. Tetrahedral framework nucleic acids (tFNAs) are novel nanomaterials that are often used as drug delivery platforms because of their structural diversity. This study formed a tFNAs-antibiotic compound (TAC) which has a strong growth inhibitory effect on Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) in vitro owing to the increased absorption of antibiotics by bacteria and improved drug movement across cell membranes. We established a mouse model of systemic peritonitis and local wound infections. The TAC exhibited good biosafety and improved the survival rate of severely infected mice, promoting the healing of local infections. In addition to the better transport of antibiotics to the target, the TAC may also enhance immunity by regulating the differentiation of M1 and M2 macrophages, providing a new option for the treatment of infections.

Iripin-1, a new anti-inflammatory tick serpin, inhibits leukocyte recruitment in vivo while altering the levels of chemokines and adhesion molecules.

Serpins are widely distributed and functionally diverse inhibitors of serine proteases. Ticks secrete serpins with anti-coagulation, anti-inflammatory, and immunomodulatory activities via their saliva into the feeding cavity to modulate host's hemostatic and immune reaction initiated by the insertion of tick's mouthparts into skin. The suppression of the host's immune response not only allows ticks to feed on a host for several days but also creates favorable conditions for the transmission of tick-borne pathogens. Herein we present the functional and structural characterization of Iripin-1 (Ixodes ricinus serpin-1), whose expression was detected in the salivary glands of the tick Ixodes ricinus, a European vector of tick-borne encephalitis and Lyme disease. Of 16 selected serine proteases, Iripin-1 inhibited primarily trypsin and further exhibited weaker inhibitory activity against kallikrein, matriptase, and plasmin. In the mouse model of acute peritonitis, Iripin-1 enhanced the production of the anti-inflammatory cytokine IL-10 and chemokines involved in neutrophil and monocyte recruitment, including MCP-1/CCL2, a potent histamine-releasing factor. Despite increased chemokine levels, the migration of neutrophils and monocytes to inflamed peritoneal cavities was significantly attenuated following Iripin-1 administration. Based on the results of in vitro experiments, immune cell recruitment might be inhibited due to Iripin-1-mediated reduction of the expression of chemokine receptors in neutrophils and adhesion molecules in endothelial cells. Decreased activity of serine proteases in the presence of Iripin-1 could further impede cell migration to the site of inflammation. Finally, we determined the tertiary structure of native Iripin-1 at 2.10 Å resolution by employing the X-ray crystallography technique. In conclusion, our data indicate that Iripin-1 facilitates I. ricinus feeding by attenuating the host's inflammatory response at the tick attachment site.

Uncovering the anti-inflammatory mechanisms of phenolic-enriched maple syrup extract in lipopolysaccharide-induced peritonitis in mice: insights from data-independent acquisition proteomics analysis.

Our group has previously reported on the phytochemical composition and biological activities of a phenolic-enriched maple syrup extract (MSX), which showed promising anti-inflammatory effects in several disease models including diabetes and Alzheimer's disease. However, the efficacious doses of MSX and its molecular targets involved in the anti-inflammatory effects are not fully elucidated. Herein, the efficacy of MSX in a peritonitis mouse model was evaluated in a dose-finding study and the underlying mechanisms were explored using data-independent acquisition (DIA) proteomics assay. MSX (at 15, 30 and 60 mg kg-1) alleviated lipopolysaccharide-induced peritonitis by reducing the levels of pro-inflammatory cytokines including interleukin-1 beta (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) in the serum and major organs of the mice. Furthermore, DIA proteomics analyses identified a panel of proteins that were significantly altered (both up- and down-regulated) in the peritonitis group, which were counteracted by the MSX treatments. MSX treatment also modulated several inflammatory upstream regulators including interferon gamma and TNF. Ingenuity pathway analysis suggested that MSX may modulate several signaling pathways in the processes of initiation of cytokine storm, activation of liver regeneration, and suppression of hepatocyte apoptosis. Together, these proteomic and in vivo findings indicate that MSX could regulate inflammation signaling pathways and modulate inflammatory markers and proteins, providing critical insight to its therapeutic potential.

Ajania purpurea Extract Attenuates LPS-Induced Inflammation in RAW264.7 Cells and Peritonitis Mice.

Macrophages have important roles in the progression of inflammation. Ajania purpurea Shih. is a member of the Ajania Poljakor family that grows in Tibet (China). Extracts from plants in this genus have anti-bacterial and anti-inflammatory properties. However, there are few reports on the activity and mechanism of Ajania purpurea. Here, we confirmed the anti-inflammatory effect of Ajania purpurea Shih. ethanol extract (EAPS) by examining the levels of inflammatory factors in a mouse model of peritonitis and RAW264.7 cells. The main components of EAPS detected by LC-MS analysis included piperine and chlorogenic acid. In particular, in lipopolysaccharide (LPS)-induced RAW264.7 cells, EAPS inhibited the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in LPS-induced RAW264.7 cells, lowered the levels of nitric oxide (NO) and prostaglandin E2 (PGE2), as well as the release of inflammatory factors such as tumor necrosis factor-alpha (TNF-α) and pro-inflammatory cytokines such as interleukin (IL)-1β and IL-6. In addition, Western blot analysis and immunofluorescence staining verified that EAPS inhibited the activity of the nuclear factor-kappaB (NF-κB) pathway by reducing the nuclear translocation of the p65 subunit. Furthermore, in a mouse model of peritonitis, EAPS inhibited the release of inflammatory factors, as well as the recruitment of immune cells including neutrophils and macrophages. These findings indicated that EAPS suppressed LPS-induced inflammation via inhibiting the NF-κB pathway in RAW264.7 cells and mice with peritonitis. Thus, EAPS may be a viable therapeutic method for the treatment of inflammation and related disorders.

Anti-Inflammatory and Antibacterial Effects and Mode of Action of Greek Arbutus, Chestnut, and Fir Honey in Mouse Models of Inflammation and Sepsis.

Background: Honey has been shown to possess anti-inflammatory and bactericidal properties that may be useful for the prevention and treatment of infections as well as of acute and chronic inflammatory diseases. The antimicrobial potency of honey could be attributed to its physicochemical characteristics combined with the presence of certain compounds, such as hydrogen peroxide and polyphenols. Honey's bacteriostatic or bactericidal capacity varies depending on its composition and the bacterial type of each infection. Nevertheless, not all honey samples possess anti-inflammatory or antibacterial properties and their mechanism of action has not been clearly elucidated. Objectives: We therefore investigated the anti-inflammatory properties of three different honey samples that derived from different geographical areas of Greece and different botanical origins, namely, arbutus, chestnut, and fir; they were compared to manuka honey, previously known for its anti-inflammatory and antibacterial activity. Materials and Methods: To test the anti-inflammatory activity of the different samples, we utilized the in vivo model of LPS-driven inflammation, which induces septic shock without the presence of pathogens. To evaluate the antibacterial action of the same honey preparations, we utilized the cecal-slurry-induced peritonitis model in mice. Since acute inflammation and sepsis reduce the biotransformation capacity of the liver, the expression of key enzymes in the process was also measured. Results: The administration of all Greek honey samples to LPS-stimulated mice revealed a potent anti-inflammatory activity by suppressing the TNFα serum levels and the expression of TNFα and iNOS in the liver at levels comparable to those of the manuka honey, but they had no effect on IL-6 or IL-1β. It was shown that the LPS-induced suppression of CYP1A1 in the liver was reversed by Epirus and Crete fir honey, while, correspondingly, the suppression of CYP2B10 in the liver was reversed by Evros chestnut and Epirus fir honey. The effect of the same honey samples in polymicrobial peritonitis in mice was also evaluated. Even though no effect was observed on the disease severity or peritoneal bacterial load, the bacterial load in the liver was reduced in mice treated with Evros chestnut, Epiros fir, and Crete fir, while the bacterial load in the lungs was reduced in Epirus arbutus, Crete fir, and manuka honey-treated mice. Conclusion: Our findings suggest that these specific Greek honey samples possess distinct anti-inflammatory and antibacterial properties, as evidenced by the reduced production of pro-inflammatory mediators and the impaired translocation of bacteria to tissues in septic mice. Their mode of action was comparable or more potent to those of manuka honey.

A novel pentavalent vaccine candidate completely protects against Acinetobacter baumannii in a mouse model of peritonitis

Acinetobacter baumannii is considered as one of the most virulent and infectious organisms that have an increased ability to both evade host immune response and resist various classes of antibiotics, leading to life-threatening infections. Multiple virulence factors have been implicated in the high prevalence rate of A. baumannii in hospitalized and immunocompromised patients. Moreover, improper use of antibiotics has led to the emergence of extensive drug-resistant strains that urgently require alternative strategies to control this superbug. Unfortunately, the availability of a licensed vaccine against A. baumannii infections is still challenged by the vast diversity among A. baumannii strains. Here, we report the development of a novel pentavalent vaccine candidate composed of two recombinant proteins (Wza and YiaD) and a pool of capsular polysaccharides isolated from 3 clinical isolates. We tested this new vaccine in vivo in a mouse model of peritonitis against the standard strain ATCC 19606 in addition to 3 clinical isolates of A. baumannii. Immunization with this vaccine completely protected the challenged mice with 100% survival rate in the case of all the tested bacteria. Further clinical studies are urgently needed to evaluate the efficacy and safety of this proprietary vaccine to protect patients from A. baumannii lethal infections.Key points• Recombinant proteins pool (Wza and YiaD) immunization led to a synergistic immune response.• Capsular polysaccharides pool induced up to 90% protection of tested clinical isolates.• The pentavalent pool showed superiority with 100% survival of immunized mice.

Biomimetic anti-inflammatory and osteogenic nanoparticles self-assembled with mineral ions and tannic acid for tissue engineering

Bone healing involves complex processes including inflammation, induction, and remodeling. In this context, anti-inflammatory and osteoconductive multi-functional nanoparticles have attracted considerable attention for application in improved bone tissue regeneration. In particular, nanoparticles that promote suppression of inflammatory response after injury and direction of desirable tissue regeneration events are of immense interest to researchers. We herein report a one-step method to prepare multi-functional nanoparticles using tannic acid (TA) and simulated body fluid (SBF) containing multiple mineral ions. Mineral-tannic acid nanoparticles (mTNs) were rapidly fabricated in 10 min, and their size (around 250–350 nm) and chemical composition were controlled through the TA concentration. In vitro analysis using human adipose derived stem cells (hADSCs) showed that mTNs effectively scavenged reactive oxygen species (ROS) and enhanced osteogenesis of hADSCs by inducing secretion of alkaline phosphatase. mTNs also increased osteogenic marker gene expression even in the presence of ROS, which can generally arrest osteogenesis (OPN: 1.74, RUNX2: 1.90, OCN: 1.47-fold changes relative to cells not treated with mTNs). In vivo analysis using a mouse peritonitis model revealed that mTNs showed anti-inflammatory effects by decreasing levels of pro-inflammatory cytokines in blood (IL-6: 73 ± 4, TNF-α: 42 ± 2%) and peritoneal fluid (IL-6: 78 ± 2, TNF-α: 21 ± 6%). We believe that this one-step method for fabrication of multi-functional nanoparticles has considerable potential in tissue engineering approaches that require control of complex microenvironments, as required for tissue regeneration.

In Vitro and In Vivo Effect of Amikacin and Imipenem Combinations against Multidrug-Resistant E. coli.

Introduction: The emergence of multidrug-resistant (MDR) E. coli has developed worldwide; therefore, the use of antibiotic combinations may be an effective strategy to target resistant bacteria and fight life-threatening infections. The current study was performed to evaluate the in vitro and in vivo efficacy of amikacin and imipenem alone and in combination against multidrug-resistant E. coli. Methods: The combination treatment was assessed in vitro using a checkerboard technique and time-killing curve and in vivo using a peritonitis mouse model. In resistant isolates, conventional PCR and quantitative real-time PCR techniques were used to detect the resistant genes of Metallo-β-lactamase gene Imipenemase (bla-IMP) and aminoglycoside 6′-N-acetyltransferase (aac (6′)-Ib). Scanning electron microscopy was used to detect the morphological changes in the resistant isolates after treatment with each drug alone and in combination. In vitro and in vivo studies showed a synergistic effect using the tested antibiotic combinations, showing fractional inhibitory concentration indices (FICIs) of ≤0.5. Regarding the in vivo study, combination therapy indicated a bactericidal effect after 24 h. E. coli isolates harboring the resistant genes Metallo-β-lactamase gene Imipenemase (bla-IMP) and aminoglycoside 6′-N-acetyltransferase (aac (6′)-Ib) represented 80% and 66.7%, respectively, which were mainly isolated from wound infections. The lowest effect on Metallo-β-lactamase gene Imipenemase (bla-IMP) and aminoglycoside 6′-N-acetyltransferase (aac (6′)-Ib) gene expression was shown in the presence of 0.25 × MIC of imipenem and 0.5 × MIC of amikacin. The scanning electron microscopy showed cell shrinkage and disruption in the outer membrane of E. coli in the presence of the antibiotic combination. Amikacin and imipenem combination can be expected to be effective in the treatment and control of serious infections caused by multidrug-resistant (MDR) E. coli and the reduction in bacterial resistance emergence.

Exposure to Multiwall Carbon Nanotubes Promotes Fibrous Proliferation by Production of Matrix Metalloproteinase-12 via NF-κB Activation in Chronic Peritonitis

The toxicologic effects of nanomaterials, such as carbon nanotubes (CNTs), on the immune system are considerably understood. However, the precise relationship between long-term exposure to CNTs and chronic inflammation remains unclear. In this study, a mouse model of chronic peritonitis was established using i.p. injection of multiwalled CNTs treated by the Taquann method with high dispersion efficiency. Chronic peritonitis with fibrosis was observed in Taquann-treated multiwalled CNT (T-CNT)-injected mice, but not in Taquann-treated titanium dioxide-injected mice. Invivo and invitro experiments showed that matrix metalloproteinase-12 (MMP-12) of macrophages was up-regulated by T-CNT to enhance fibroblast activation and profibrotic molecule expression in fibroblasts. In addition, T-CNT-induced peritonitis reduced MMP-12 expression in Nfκb1-/- mice, suggesting that MMP-12-producing macrophages play a key role in chronic inflammation due to T-CNT exposure through NF-κB activation. The results of this study could be helpful in understanding the molecular toxicity of nanomaterial and chronic inflammation.

Tea Tree Oil Nanoemulsion Potentiates Antibiotics against Multidrug-Resistant Escherichia coli.

Extensive efforts are underway to overcome the rising prevalence of antibiotic resistance. Combination therapy may be a potential method to treat multidrug-resistant (MDR) bacterial infections. In this study, tea tree essential oil (TTO) nanoemulsion (nanoTTO) was used in combination with antibiotics to kill microbes. Results showed that nanoTTO enhanced the activities of multiple antibiotics against MDR Escherichia coli (E. coli), and its antimicrobial activity was not changed against bacteria that were cultured in the presence of nanoTTO for 30 passages. Further studies to visualize and quantify intracellular antibiotics concentrations identified that nanoTTO increased the drug accumulation in MDR E. coli by disrupting outer and inner membranes and inhibiting the AcrAB-TolC efflux pump involved in membrane permeability. In addition, nanoTTO was effective in enhancing antibiotic efficacy in the Galleria mellonella infection model and mouse peritonitis model, suggesting a potential strategy against MDR bacterial infections.

Card9 protects fungal peritonitis through regulating Malt1-mediated activation of autophagy in macrophage

Fungal peritonitis is an inflammatory condition of the peritoneum which occurs secondary to peritoneal dialysis. Most cases of peritonitis are caused by microbial invasion into the peritoneal cavity, resulting in high morbidity and mortality. Unlike bacterial peritonitis, little is known on fungal peritonitis. Card9, an adapter protein, plays a critical role in anti-fungal immunity. In this study, by using zymosan-induced peritonitis and C. albicans-induced peritonitis mouse model, we demonstrated that fungal peritonitis was exacerbated in Card9-/- mice, compared with WT mice. Next, we found the autophagy activation of peritonealmacrophages was impaired in Card9-/- peritonitis mice. The autophagy agonist, MG132, ameliorated peritonitis in Card9-/- mice. The result of microarray analysis indicates Malt1 was significantly decreased in Card9-/- peritonitis mice. Furthermore, we demonstrated that Malt1 interacts with P62 and mediates the function of P62 to clear ubiquitinated proteins. After overexpression of Malt1, impaired autophagy activation caused by Card9 deficient was significantly rescued. Together, our results indicate that Card9 protects fungal peritonitis by regulating Malt1-mediated autophagy in macrophages. Our research provides a new idea for the pathogenesis of fungal peritonitis, which is of great significance for the clinical treatment of fungal peritonitis.

Optimization of Antibacterial Activity in Tibetan Swine α-Helix Peptide TP by Site-Directed Mutagenesis.

Antimicrobial peptides (AMPs) have attracted extensive attention because of their broad-spectrum antibacterial activity and low level of induced bacterial resistance. However, the development of some natural AMPs does not consider the perfect balance of structural characteristics, resulting in some empirical and controversial practices still existing. To further explore and complete the relationship between parameters and function of α-helix peptide, in this study, the natural antimicrobial peptide TP secreted from Bacillus strain of Tibetan pigs was selected as a template to investigate the effect of systematic mutations in the hydrogen bond formation site of the α-helical antimicrobial peptide on the activity and cell selectivity of the antimicrobial peptide. The target peptide TP(i+4) 1&2&5 with modification of two pairs of positively charged amino acids and a pair of hydrophobic amino acids showed excellent antibacterial ability and the best selectivity index (SI = 64) in vitro. At the same time, TP(i+4) 1&2&5 remained active in the presence of physiological salts and serum. The results of fluorescence, flow cytometry, and electron microscopy showed that the optimized sequences showed good antibacterial activity by membrane infiltration and membrane destruction. The potential of TP(i+4) 1&2&5 in vivo was tested in a mouse peritonitis model. Organ bacterial loads in the liver, kidney, spleen, and lungs of mice treated with TP(i+4) 1&2&5 were significantly lower compared to the infected group (p < 0.05). Overall, these findings contribute to the design and optimization of antimicrobial peptides with high activity and low toxicity and may accelerate the clinical application of antimicrobial peptides.

Subinhibitory Concentrations of Antibiotics Exacerbate Staphylococcal Infection by Inducing Bacterial Virulence.

ABSTRACTAntibiotics are widely used for the treatment of bacterial infections. However, injudicious use of antibiotics based on an empirical method may lead to the emergence of resistant strains. Despite appropriate administration of antibiotics, their concentrations may remain subinhibitory in the body, due to individual variations in tissue distribution and metabolism rates. This may promote bacterial virulence and complicate the treatment strategies. To investigate whether the administration of certain classes of antibiotics will induce bacterial virulence and worsen the infection under in vivo conditions. Different classes of antibiotics were tested in vitro for their ability to induce virulence in a methicillin-resistant S. aureus strain Mu3 and clinical isolates. Antibiotic-induced pathogenicity was assessed in vivo using mouse peritonitis and bacteremia models. In vitro, β-lactam antibiotics and tetracyclines induced the expression of multiple surface-associated virulence factors as well as the secretion of toxins. In peritonitis and bacteremia models, mice infected with MRSA and treated with ampicillin, ceftazidime, or tetracycline showed enhanced bacterial pathogenicity. The release of induced virulence factors in vivo was confirmed in a histological examination. Subinhibitory concentrations of antibiotics belonging to β-lactam and tetracycline aggravated infection by inducing staphylococcal virulence in vivo. Thus, when antibiotics are required, it is preferable to employ combination therapy and to initiate the appropriate treatment plan, following diagnosis. Our findings emphasize the risks associated with antibiotic-based therapy and underline the need for alternative therapeutic options.IMPORTANCE Antibiotics are widely applied to treat infectious diseases. Empirically treatment with incorrect antibiotics, or even correct antibiotics always falls into subinhibitory concentrations, due to dosing, distribution, or secretion. In this study, we have systematically evaluated in vitro virulence induction effect of antibiotics and in vivo exacerbated infection. The major highlight of this work is to prove the β-lactam and tetracyclines antibiotics exacerbated disease is due to their induction effect on staphylococcal virulence. This phenomenon is common and suggests that if β-lactam antibiotics remain the first line of defense during empirical therapy, we either need to increase patient reliability or the treatment approach may improve in the future when paired with anti-virulence drugs.