Unmasking the dynamics of Mycoplasma gallisepticum: deciphering HD11 macrophage polarization for innovative infection control strategies.

Mycoplasma gallisepticum (MG) is a highly contagious avian respiratory pathogen characterized by rapid spread, widespread distribution, and long-term persistence of infection. Previous studies have shown that chicken macrophage HD11 cells play a critical role in the replication and immunomodulation of MG. Macrophages are multifunctional immunomodulatory cells that polarize into different functions and morphologies in response to exogenous stimuli. However, the effect of MG infection on HD11 polarization is not well understood. In this study, we observed a time-dependent increase in both the expression of the MG-related virulence protein pMGA1.2 and the copy number of MG upon MG infection. Polarization studies revealed an upregulation of M1-type marker genes in MG-infected HD11 cells, suggesting that MG mainly induces HD11 macrophages towards M1-type polarization. Furthermore, MG activated the inflammatory vesicle NLRP3 signaling pathway, and NLRP3 inhibitors affected the expression of M1 and M2 marker genes, indicating the crucial regulatory role of the NLRP3 signaling pathway in MG-induced polarization of HD11 macrophages. Our findings reveal a novel mechanism of MG infection, namely the polarization of MG-infected HD11 macrophages. This discovery suggests that altering the macrophage phenotype to inhibit MG infection may be an effective control strategy. These findings provide new perspectives on the pathogenic mechanism and control measures of MG.

Avian safety guardian: Luteolin restores Mycoplasma gallisepticum-induced immunocompromise to improve production performance via inhibiting the IL-17/NF-kB pathway.

Mycoplasma gallisepticum (MG) is a major pathogen causing chronic respiratory disease (CRD) in chickens. Exposure to MG poses a constant threat to chicken health and causes substantial economic losses. Antibiotics are the main treatment for MG infections, but have to struggle with antibiotic residues and MG resistance. To date, no safe and more effective prevention or treatment for MG infections has been identified. Luteolin (Lut) is a natural flavonoid compound known for its excellent anti-viral, anti-bacterial, immunoregulatory, and anti-inflammatory pharmacological activities. Herein, we established an MG-infected model using partridge shank chickens and chicken-like macrophages (HD11 cells) to investigate the effect and potential mechanism of Lut against MG-induced immune damage. According to our findings, Lut significantly inhibited the expression of MG adhesion protein (pMGA1.2) in vivo and in vitro. Lut effectively mitigated the MG-induced decrease in body weight gain, feed conversion ratio, survival rate, and serum IgG and IgA levels. Lut directly repaired MG-induced spleen and thymus damage by histopathological analysis. Furthermore, network pharmacology analysis revealed that Lut most probably resisted MG infection through the IL-17/NF-kB pathway. In vivo and in vitro experiments, Lut significantly suppressed the increase in key protein IL-17A, TRAF6, p-p65, and p-IkBα in the IL-17/NF-kB pathway. Meanwhile, Lut markedly alleviated MG-induced the increase of pro-inflammatory cytokines TNF-α, IL-6, IL-1ß, pro-apoptotic genes caspase3 and caspase9, while promoting the expression of anti-apoptotic genes Bcl-2 and Bcl-XL. In summary, Lut effectively suppressed MG colonization, alleviated MG-induced the production performance degradation, inflammatory responses, and immune damage by inhibiting the IL-17/ NF-kB pathway. This study indicates Lut can serve as a safe and effective antibiotic alternative drug for preventing and treating MG-induced CRD. It also provides new evidence to explore the molecular mechanisms of MG infection.

Baicalin ameliorates Mycoplasma gallisepticum-induced inflammatory injury via inhibiting STIM1-regulated ceramide accumulation in DF-1 cells.

Mycoplasma gallisepticum (MG) is dependent on its host for many nutrients due to the loss of many important metabolic pathways. Ceramide is a sphingolipid that regulates multiple cellular processes in eukaryotic cell. Several studies highlighted the crucial role of ceramide on the pathogenesis of various pathogens. This study aimed to determine whether ceramide plays a crucial role in the pathogenesis of MG. Based on an MG infection model in DF-1 cells, the results revealed that MG infection induced ceramide accumulation in DF-1 cells. Inhibiting the de novo synthesis of ceramide significantly inhibited MG proliferation and inflammatory injury caused by MG in DF-1 cells. Meanwhile, MG infection led to endoplasmic reticulum stress, and pharmacologic inhibition of endoplasmic reticulum stress prevented ceramide accumulation and MG proliferation in DF-1 cells, alleviating the inflammatory injury caused by MG. In addition, MG infection significantly promoted expression level of stromal interaction molecule 1 (STIM1), thus induced calcium overload and oxidative stress. Furthermore, inhibition of STIM1 expression partially restored calcium homeostasis and mitigated oxidative stress, thus alleviated endoplasmic reticulum stress. Importantly, the inflammatory injury caused by MG were partially ameliorated by baicalin treatment (20 µg/mL) through downregulating STIM1 expression. In summary, these results suggests that ceramide accumulation through the de novo pathway plays an important role to promote MG proliferation and baicalin can alleviate MG infection induced inflammatory injury via regulating STIM1-related oxidative stress, endoplasmic reticulum stress and ceramide accumulation in DF-1 cells.

Hydroxytyrosol mitigates Mycoplasma gallisepticum-induced pulmonary injury through downregulation of the NF-κB/NLRP3/IL-1ß signaling pathway in chicken.

In this study, the anti-inflammatory and antiapoptotic effects of hydroxytyrosol (HT) in Mycoplasma gallisepticum (MG)-infected chicken were investigated, and the underlying molecular mechanisms were explored. The results revealed severe ultrastructural pathological changes after MG infection in the lung tissue of chicken, including inflammatory cell infiltration, thickening of the lung chamber wall, visible cell swelling, mitochondrial cristae rupture, and ribosome shedding. MG possibly activated the nuclear factor κB (NF-κB)/nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3)/interleukin (IL)-1ß signaling pathway in the lung. However, HT treatment significantly ameliorated MG-induced pathological damage of the lung. HT reduced the magnitude of pulmonary injury after MG infection by reducing apoptosis and releasing the proinflammatory factors. Compared with the MG-infected group, the HT-treated group exhibited significant inhibition of the expression of NF-κB/NLRP3/IL-1ß signaling-pathway-related genes; for example, the expressions of NF-κB, NLRP3, caspase-1, IL-1ß, IL-2, IL-6, IL-18, and TNF-α significantly decreased (P < 0.01 or <0.05). In conclusion, HT effectively inhibited MG-induced inflammatory response and apoptosis and protected the lung by blocking the activation of NF-κB/NLRP3/IL-1ß signaling pathway and reducing the damage caused by MG infection in chicken. This study revealed that HT may be a suitable and effective anti-inflammatory drug against MG infection in chicken.

Methylsulfonylmethane ameliorates inflammation via NF-κB and ERK/JNK-MAPK signaling pathway in chicken trachea and HD11 cells during Mycoplasma gallisepticum infection.

Mycoplasma gallisepticum (MG) is an avian pathogen that commonly causes respiratory diseases in poultry. Methylsulfonylmethane (MSM) is a sulfur-containing natural compound that could alleviate inflammatory injury through its excellent anti-inflammatory and antioxidant properties. However, it is still unclear whether MSM prevents MG infection. The purpose of this study is to determine whether MSM has mitigative effects on MG-induced inflammatory injury in chicken and chicken like macrophages (HD11 cells). In this research, White Leghorn chickens and HD11 cells were used to build the MG-infection model. Besides, the protective effects of MSM against MG infection were evaluated by detecting MG colonization, histopathological changes, oxidative stress and inflammatory injury of trachea, and HD11 cells. The results revealed that MG infection induced inflammatory injury and oxidative stress in trachea and HD11 cells. However, MSM treatment significantly ameliorated oxidative stress, partially alleviated the abnormal morphological changes and reduced MG colonization under MG infection. Moreover, MSM reduced the mRNA expression of proinflammatory cytokines-related genes and decreased the number of death cells under MG infection. Importantly, the protective effects of MSM were associated with suppression of nuclear factor-kappa B (NF-κB) and extracellular signal-related kinases (ERK)/Jun amino terminal kinases (JNK)-mitogen-activated protein kinases (MAPK) pathway in trachea and HD11 cells. These results proved that MSM has protective effects on MG-induced inflammation in chicken, and supplied a better strategy for the protective intervention of this disease.

Baicalin alleviates Mycoplasma gallisepticum-induced oxidative stress and inflammation via modulating NLRP3 inflammasome-autophagy pathway.

Baicalin is a well-known flavonoid compound, possess therapeutic potential against inflammatory diseases. Previous studies reported that Mycoplasma gallisepticum (MG) induced inflammatory response and immune dysregulation inside the host body. However, the underlying molecular mechanisms of baicalin against MG-infected chicken-like macrophages (HD11 cells) are still illusive. Oxidant status and total reactive oxygen species (ROS) were detected by ELISA assays and flow cytometry respectively. Mitochondrial membrane potential (ΔΨM) was evaluated by immunofluorescence microscopy. Transmission electron microscopy was used for ultrastructural analysis. The hallmarks of inflammation and autophagy were determined by western blotting. Oxidative stress and reactive oxygen species (ROS) were significantly enhanced in the MG-infected HD11 cells. MG infection caused disruption in the mitochondrial membrane potential (ΔΨM) compared to the control conditions. Meanwhile, baicalin treatment reduced MG-induced reactive oxygen species (ROS), oxidative stress and alleviated the disruption in ΔΨM. The activities of inflammatory markers were significantly enhanced in the MG-infected HD11 cells. Increased protein expressions of TLR-2-NF-κB pathway, NLRP3-inflammasome and autophagy-related proteins were detected in the MG-infected HD11 cells. Besides, baicalin treatment significantly reduced the protein expressions of TLR-2-NF-κB pathway and NLRP3 inflammasome. While, the autophagy-related proteins were significantly enhanced with baicalin treatment in a dose-dependent manner in the MG-infected HD11 cells. The results showed that baicalin prevented HD11 cells from MG-induced oxidative stress and inflammation via the opposite modulation of TLR-2-NF-κB-mediated NLRP3-inflammasome pathway and autophagy, and baicalin could be a promising candidate for the prevention of inflammatory effects caused by MG-infection in macrophages.

Baicalin attenuated Mycoplasma gallisepticum-induced immune impairment in chicken bursa of fabricius through modulation of autophagy and inhibited inflammation and apoptosis.

BACKGROUND: Mycoplasma gallisepticum (MG) is the primary etiologic agent of chronic respiratory disease in poultry. However, the mechanism underlying MG-induced immune dysregulation in chicken is still elusive. Baicalin shows excellent anti-bacterial, anti-inflammatory, anti-carcinogenic and anti-viral properties. In the present study, the preventive effects of baicalin against immune impairment in chicken bursa of fabricius (BF) were studied in an MG infection model. RESULTS: Histopathological examination showed increased inflammatory cell infiltrations and fragmented nuclei in the model group. Ultrastructural analysis revealed the phenomenon of apoptosis in bursal cells, along with the deformation of mitochondrial membrane and swollen mitochondria in the model group. However, these abnormal morphological changes were partially alleviated by baicalin. Meanwhile, baicalin treatment attenuated the level of proinflammatory cytokines, and suppressed nuclear factor-kappa B expression at both protein and mRNA level. Terminal deoxynucleotidyl transferase-mediated dUTP nick endlabeling assay showed extensive apoptosis in BF in the model group. The mRNA and protein expression levels of apoptosis-related genes were upregulated in BF, while baicalin treatment significantly alleviated apoptosis in BF. In addition, alterations in mRNA and protein expression levels of autophagy-related genes and mitochondrial dynamics proteins were significantly alleviated by baicalin. Moreover, baicalin treatment significantly attenuated MG-induced decrease in CD8+ cells and reduced bacterial load in chicken BF compared to the model group. CONCLUSIONS: These results suggested that baicalin could effectively inhibit MG-induced immune impairment and alleviate inflammatory responses and apoptosis in chicken BF. © 2020 Society of Chemical Industry.

Mycoplasma gallisepticum infection triggered histopathological changes, oxidative stress and apoptosis in chicken thymus and spleen.

Previous studies mainly focused on the inflammatory responses caused by Mycoplasma gallisepticum (MG) in the chicken respiratory mucosa, setting the stage for chronic infection and disease manifestation. However, the underlying mechanism is still unknown. Spleen and thymus are important immune organs, which play a critical role in eliciting protective immune responses to ensure healing process and elimination of harmful stimuli. In the present study, the effects of MG infection on chicken spleen and thymus were investigated. The results showed that MG infection reduced antioxidant activities and induced oxidative stress in the spleen and thymus tissues. Histological examination showed normal morphology of chicken spleen and thymus in control group compared to MG infection group. In contrast, increased number of necrotic and nuclear debris, lymphocytolysis, prominent reticuloepithelial cells and loose arrangement of cells in the spleen and thymus were seen in MG-infected chickens. Ultrastructural analysis indicated nuclear and mitochondrial damage including mitochondrial swelling, deformation of nuclear membrane and congestion of chromatin material in MG infection group. The mRNA and protein expression of apoptosis-related genes were significantly upregulated in the spleen and thymus of MG-infected chickens compared to control group. Moreover, Terminal deoxynucleotidyl transferase-mediated dUTP nick endlabeling (TUNEL) assay results suggested that MG infection increased the number of positive-stained nuclei in the spleen and thymus. Meanwhile, the mRNA expression of mitochondrial dynamics in the spleen and thymus were altered by MG infection. In summary, these results showed that MG induced oxidative stress and apoptosis, which could be the possible causes associated with the immune damage, structural impairment and disease pathogenesis of MG infection.

A respiratory commensal bacterium acts as a risk factor for Mycoplasma gallisepticum infection in chickens.

Commensal microbiota has been shown to play an important role in local infections. However, the correlation between host respiratory microbiota and Mycoplasma gallisepticum (MG) infection is not well characterized. Here, the results of 16S rRNA sequencing showed that MG infection correlated with alteration in respiratory microbiota of chickens characterized by decreased richness and diversity. To explore whether respiratory microbiota contributed to MG infection, an antibiotics cocktail was used to deplete respiratory microbiota. It has been found that depletion of respiratory Gram-positive and Gram-negative bacteria promoted MG infection, as reflected in the form of increased MG colonization, pro-inflammatory cytokines and proteins expression, and severe lung damage compared to the control group. Importantly, depletion of Gram-negative bacteria in respiratory tract mitigated MG infection, which indicated that certain Gram-negative bacteria may promote MG infection. By reconstitution of individual cultivable respiratory tract bacteria in antibiotic-treated chickens, a respiratory commensal microbe Serratia marcescens was identified to facilitate MG infection. We further found that Serratia marcescens may promote MG infection by downregulating Mucin 2 (MUC2) and tight junction related gene mRNA expression levels in trachea and lung tissues. Together, our data demonstrated that MG infection induced disturbed respiratory microbiota and the specific respiratory commensal bacterium Serratia marcescens could promote MG infection, and thus expand our understanding of the pathogenesis of MG infection.

House finches with high coccidia burdens experience more severe experimental Mycoplasma gallisepticum infections.

Parasites co-infecting hosts can interact directly and indirectly to affect parasite growth and disease manifestation. We examined potential interactions between two common parasites of house finches: the bacterium Mycoplasma gallisepticum that causes conjunctivitis and the intestinal coccidian parasite Isospora sp. We quantified coccidia burdens prior to and following experimental infection with M. gallisepticum, exploiting the birds' range of natural coccidia burdens. Birds with greater baseline coccidia burdens developed higher M. gallisepticum loads and longer lasting conjunctivitis following inoculation. However, experimental inoculation with M. gallisepticum did not appear to alter coccidia shedding. Our study suggests that differences in immunocompetence or condition may predispose some finches to more severe infections with both pathogens.

Growth and humoral immune effects of dietary Original XPC in layer pullets challenged with Mycoplasma gallisepticum.

Effects of dietary Original XPC (XPC) in commercial layer pullets challenged with the virulent, low passage R strain of Mycoplasma gallisepticum (Rlow MG) were investigated. Hy-Line W-36 pullets sourced from MG-clean breeders were fed a basal diet with or without (CON) XPC (1.25 kg/metric ton) from hatch until 12 wk of age (woa). At 8 and 10 woa, half of the birds in each dietary treatment were challenged with Rlow MG. Body weight was recorded at 3, 8, and 12 woa, and ovary, ceca, and bursa weights were recorded at 3 and 12 woa. Blood samples were taken immediately before the initial Rlow MG challenge at 8 woa and again at 12 woa to test for IgM and IgG antibody production against MG. All birds were evaluated for MG lesion scores at 12 woa. Regardless of challenge, inclusion of XPC in the diet did not significantly alter BW at 3 or 8 woa or relative organ weights at 3 or 12 woa. However, at 12 woa, BW of XPC-fed birds, regardless of challenge was significantly (P = 0.0038) heavier than CON by 25.7 g. All birds tested negative for MG antibodies before the 8 woa challenge. Respective percentage serum plate agglutination and ELISA positive birds at 12 woa were 0 and 0% (CON, nonchallenged), 1.4 and 0% (XPC, nonchallenged), 100 and 47.2% (CON, challenged), and 100 and 50.0% (XPC, challenged). Diet did not significantly affect ELISA titers, but they were significantly (P < 0.0001) increased due to challenge. Furthermore, lesion scores were significantly higher for Rlow MG-challenged birds (P = 0.0012), and dietary treatment with XPC in challenged birds numerically reduced MG lesion scores from 0.278 to 0.194. In conclusion, although dietary XPC did not significantly alter the humoral immune response, antibody titer levels, or severity of MG lesions in layer pullets that were or were not challenged with Rlow MG, it led to an increase in their rate of growth through 12 woa.

Multiple differences in pathogen-host cell interactions following a bacterial host shift.

Novel disease emergence is often associated with changes in pathogen traits that enable pathogen colonisation, persistence and transmission in the novel host environment. While understanding the mechanisms underlying disease emergence is likely to have critical implications for preventing infectious outbreaks, such knowledge is often based on studies of viral pathogens, despite the fact that bacterial pathogens may exhibit very different life histories. Here, we investigate the ability of epizootic outbreak strains of the bacterial pathogen, Mycoplasma gallisepticum, which jumped from poultry into North American house finches (Haemorhous mexicanus), to interact with model avian cells. We found that house finch epizootic outbreak strains of M. gallisepticum displayed a greater ability to adhere to, invade, persist within and exit from cultured chicken embryonic fibroblasts, than the reference virulent (R_low) and attenuated (R_high) poultry strains. Furthermore, unlike the poultry strains, the house finch epizootic outbreak strain HF_1994 displayed a striking lack of cytotoxicity, even exerting a cytoprotective effect on avian cells. Our results suggest that, at epizootic outbreak in house finches, M. gallisepticum was particularly adept at using the intra-cellular environment, which may have facilitated colonisation, dissemination and immune evasion within the novel finch host. Whether this high-invasion phenotype is similarly displayed in interactions with house finch cells, and whether it contributed to the success of the host shift, remains to be determined.

Mycoplasma gallisepticum triggers immune damage in the chicken thymus by activating the TLR-2/MyD88/NF-κB signaling pathway and NLRP3 inflammasome.

Previous studies reported that Mycoplasma gallisepticum (MG) causes immune dysregulation in chickens. However, the underlying mechanisms of immune dysregulation in chickens are still unclear. The thymus is a primary lymphoid organ where the proliferation, differentiation and selection of T-lymphocytes occur, whereas T-lymphocytes play a crucial role in innate immune responses. To evaluate the effects of MG-infection on chicken thymus, White Leghorn chickens were divided into (1) control group and (2) MG-infection group. ATPase activities were detected by commercial kits. The hallmarks of inflammation, autophagy and energy metabolism were examined in chicken thymus tissues by histopathology, transmission electron microscopy, immunofluorescence microscopy, RT-PCR and western blotting. Immunofluorescence examination revealed that the number of CD8+ lymphocytes has significantly reduced in MG-infection group. In addition, morphological analysis revealed that MG induced inflammatory cells infiltration. The mitochondria were swollen and chromatin material was condensed in MG-infection group. The mRNA and protein expression results showed that MG-infection triggered the nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing 3 (NLRP3) inflammasome through TLR-2/MyD88/NF-κB signaling pathway. Meanwhile, the expressions of autophagy-related genes were reduced both at mRNA and protein level in MG-infection group. While, ATPase activities and the expression of energy metabolism-related genes were reduced in the thymus of MG-infected chickens. These results showed that MG-infection triggered inflammatory response through TLR-2/MyD88/NF-κB signaling pathway, activated NLRP3 inflammasome, reduced the level of autophagy and impaired energy metabolism, which then lead to tissue damage in chicken thymus. The data provide new insights in MG-infection-mediated immune damage and provide possible therapeutic targets for future targeted therapy.

Baicalin mitigated Mycoplasma gallisepticum-induced structural damage and attenuated oxidative stress and apoptosis in chicken thymus through the Nrf2/HO-1 defence pathway.

The thymus is a primary lymphoid organ and plays a critical role in the immune response against infectious agents. Baicalin is a naturally derived flavonoid famous for its pharmacological properties, but the preventive effects of baicalin against immune impairment remain unclear. We examined this effect in the context of Mycoplasma gallisepticum (MG) infection-induced structural damage in the chicken thymus. Histopathological examination showed that the compact arrangement of cells in the thymus was lost in the MG-infected group. Inflammatory cell infiltration and nuclear debris accumulated, and the boundary between the cortex and medulla was not clearly visible. The mRNA and protein expression of apoptosis-related genes were significantly increased in the MG-infected group compared to the control group and the baicalin group. The number of positively stained nuclei in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay were increased in the MG-infected group. In addition, electron microscopic examination showed chromatin condensation, mitochondrial swelling and apoptotic vesicles in the MG-infected group. However, baicalin treatment significantly alleviated the oxidative stress and apoptosis induced by MG infection. Importantly, the abnormal morphology was partially ameliorated by baicalin treatment. Compared to the MG-infected group, the baicalin-treated group showed significantly reduced expression of apoptosis-related genes at both the mRNA and protein levels. Meanwhile, the nuclear factor erythroid 2-related factor 2 (Nrf2) signalling pathway and downstream genes were significantly upregulated by baicalin to counteract MG-induced oxidative stress and apoptosis in the thymocytes of chickens. In summary, these findings suggest that baicalin treatment efficiently attenuated oxidative stress and apoptosis by activating the Nrf2 signalling pathway and could protect the thymus from MG infection-mediated structural and functional damage.

gga-miR-21 modulates Mycoplasma gallisepticum (HS strain)-Induced inflammation via targeting MAP3K1 and activating MAPKs and NF-κB pathways.

Mycoplasma gallisepticum (MG) can target host cells and cause chronic respiratory disease (CRD) in chickens that is characterized by pMGA and concomitant. Although microRNAs (miRNAs) have been manifested are crucial regulatory noncoding RNAs with important effects on microbial pathogenesis and inflammatory response, how miRNAs regulate MG-induced inflammation remains to be discovered. The results showed that gga-miR-21 was up-regulated in MG-infected chicken embryonic lungs and MG infection of chicken embryo fibroblast cells (DF-1) compared with the control group. Overexpression of gga-miR-21 increased the inflammatory cytokines production, including tumor necrosis factor alpha (TNF-α), interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and interleukin-8 (IL-8) after MG infection, knockdown of gga-miR-21 had thoroughly inverse effects. Gene expression data combined with bioinformatics analysis and luciferase reporter assays demonstrated that mitogen-activated protein kinase kinase kinase 1(MAP3K1) was a novel target of gga-miR-21. The inhibition of MAP3K1 by gga-miR-21 resulted in the accumulation of NF-κB in the nucleus, which in turn generate higher inflammatory cytokines. Furthermore, upregulation of gga-miR-21 significantly inhibited MG propagation and promoted MG-infected DF-1 cells proliferation by increasing the cell cycle progression and suppressing cell apoptosis. Our study provides evidence for proinflammatory effects of gga-miR-21 which is mediated at least in part by targeting MAP3K1 in the MG-infected DF-1 cells. gga-miR-21 activates MAPKs and NF-κB signaling pathways via targeting MAP3K1, and then promotes the production of inflammatory cytokines and cell proliferation by increasing the cell cycle progression and suppressing cell apoptosis to defend against MG infection.

Baicalin ameliorates oxidative stress and apoptosis by restoring mitochondrial dynamics in the spleen of chickens via the opposite modulation of NF-κB and Nrf2/HO-1 signaling pathway during Mycoplasma gallisepticum infection.

Mycoplasma gallisepticum (MG) infection produces a profound inflammatory response in the respiratory tract and evade birds' immune recognition to establish a chronic infection. Previous reports documented that the flavonoid baicalin possess potent anti-inflammatory, and antioxidant activities. However, whether baicalin prevent immune dysfunction is largely unknown. In the present study, the preventive effects of baicalin were determined on oxidative stress generation and apoptosis in the spleen of chickens infected with MG. Histopathological examination showed abnormal morphological changes including cell hyperplasia, lymphocytes depletion, and the red and white pulp of spleen were not clearly visible in the model group. Oxidative stress-related parameters were significantly (P < 0.05) increased in the model group. However, baicalin treatment significantly (P < 0.05) ameliorated oxidative stress and partially alleviated the abnormal morphological changes in the chicken spleen compared to model group. Terminal deoxynucleotidyl transferase-mediated dUTP nick endlabeling assay results, mRNA, and protein expression levels of mitochondrial apoptosis-related genes showed that baicalin significantly attenuated apoptosis. Moreover, baicalin restored the mRNA expression of mitochondrial dynamics-related genes and maintain the balance between mitochondrial inner and outer membranes. Intriguingly, the protective effects of baicalin were associated with the upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2)/Heme oxygenase-1 (HO-1) pathway and suppression of nuclear factor-kappa B (NF-κB) pathway in the spleen of chicken. In summary, these findings indicated that baicalin promoted mitochondrial dynamics imbalance and effectively prevents oxidative stress and apoptosis in the splenocytes of chickens infected with MG.

Behaviors and Energy Source of Mycoplasma gallisepticum Gliding.

Mycoplasma gallisepticum, an avian-pathogenic bacterium, glides on host tissue surfaces by using a common motility system with Mycoplasma pneumoniae In the present study, we observed and analyzed the gliding behaviors of M. gallisepticum in detail by using optical microscopes. M. gallisepticum glided at a speed of 0.27 ± 0.09 µm/s with directional changes relative to the cell axis of 0.6 degree ± 44.6 degrees/5 s without the rolling of the cell body. To examine the effects of viscosity on gliding, we analyzed the gliding behaviors under viscous environments. The gliding speed was constant in various concentrations of methylcellulose but was affected by Ficoll. To investigate the relationship between binding and gliding, we analyzed the inhibitory effects of sialyllactose on binding and gliding. The binding and gliding speed sigmoidally decreased with sialyllactose concentration, indicating the cooperative binding of the cell. To determine the direct energy source of gliding, we used a membrane-permeabilized ghost model. We permeabilized M. gallisepticum cells with Triton X-100 or Triton X-100 containing ATP and analyzed the gliding of permeabilized cells. The cells permeabilized with Triton X-100 did not show gliding; in contrast, the cells permeabilized with Triton X-100 containing ATP showed gliding at a speed of 0.014 ± 0.007 µm/s. These results indicate that the direct energy source for the gliding motility of M. gallisepticum is ATP.IMPORTANCE Mycoplasmas, the smallest bacteria, are parasitic and occasionally commensal. Mycoplasma gallisepticum is related to human-pathogenic mycoplasmas-Mycoplasma pneumoniae and Mycoplasma genitalium-which cause so-called "walking pneumonia" and nongonococcal urethritis, respectively. These mycoplasmas trap sialylated oligosaccharides, which are common targets among influenza viruses, on host trachea or urinary tract surfaces and glide to enlarge the infected areas. Interestingly, this gliding motility is not related to other bacterial motilities or eukaryotic motilities. Here, we quantitatively analyze cell behaviors in gliding and clarify the direct energy source. The results provide clues for elucidating this unique motility mechanism.

What Does Tolerance Mean for Animal Disease Dynamics When Pathology Enhances Transmission?

Host competence, or how well an individual transmits pathogens, varies substantially within and among animal populations. As this variation can alter the course of epidemics and epizootics, revealing its underlying causes will help predict and control the spread of disease. One host trait that could drive heterogeneity in competence is host tolerance, which minimizes fitness losses during infection without decreasing pathogen load. In many cases, tolerance should increase competence by extending infectious periods and enabling behaviors that facilitate contact among hosts. However, we argue that the links between tolerance and competence are more varied. Specifically, the different physiological and behavioral mechanisms by which hosts achieve tolerance should have a range of effects on competence, enhancing the ability to transmit pathogens in some circumstances and impeding it in others. Because tissue-based pathology (damage) that reduces host fitness is often critical for pathogen transmission, we focus on two mechanisms that can underlie tolerance at the tissue level: damage-avoidance and damage-repair. As damage-avoidance reduces transmission-enhancing pathology, this mechanism is likely to decrease host competence and pathogen transmission. In contrast, damage-repair does not prevent transmission-relevant pathology from occurring. Rather, damage-repair provides new, healthy tissues that pathogens can exploit, likely extending the infectious period and increasing host competence. We explore these concepts through graphical models and present three disease systems in which damage-avoidance and damage-repair alter host competence in the predicted directions. Finally, we suggest that by incorporating these links, future theoretical studies could provide new insights into infectious disease dynamics and host-pathogen coevolution.

Upregulated gga-miR-16-5p Inhibits the Proliferation Cycle and Promotes the Apoptosis of MG-Infected DF-1 Cells by Repressing PIK3R1-Mediated the PI3K/Akt/NF-κB Pathway to Exert Anti-Inflammatory Effect.

Mycoplasma gallisepticum (MG) mainly infects chickens to initiate chronic respiratory disease (CRD). microRNAs (miRNAs) play vital roles according to previously reported studies. Our previous study showed that gga-miR-16-5p, in MG-infected lungs of chicken embryo, was upregulated by Illumina sequencing. The study aimed to reveal what role gga-miR-16-5p plays in CRD progression. gga-miR-16-5p was upregulated in MG-infected fibroblast cells (DF-1). Phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) was demonstrated as the target gene of gga-miR-16-5p. Furthermore, PIK3R1 expression was lower in MG-infected groups than it in noninfected controls measured by qPCR. Additionally, overexpressed gga-miR-16-5p could downregulate PIK3R1 and phosphorylated serine/threonine kinase (p-Akt) to express protein, whereas there is an opposite effect on inhibition. Overexpressed gga-miR-16-5p resulted in decreased activity of tumor necrosis factor alpha (TNF-α) and the nuclear factor-kappaB (NF-κB) by qPCR. Furthermore, overexpressed gga-miR-16-5p restricted cell multiplication, cycle progression, and increased apoptosis of MG-infected DF-1 cells, whereas inhibited gga-miR-16-5p led to the opposite effect. Collectively, upregulated gga-miR-16-5p could decrease multiplication, cycle progression, and increase apoptosis of MG-infected DF-1 cells, at least partly through directly targeting PIK3R1 and inhibiting PI3K/Akt/NF-κB pathway to exert an anti-inflammatory effect. Our results will provide more experimental evidence to bring pathogenesis of MG infection to light.