Transcriptome changes upon in vitro challenge with Mycobacterium bovis in monocyte-derived macrophages from bovine tuberculosis-infected and healthy cows

Effects of oral β-cryptoxanthin administration on the transcriptomes of peripheral neutrophil and liver tissue using microarray analysis in post-weaned Holstein calves

We investigated the effects of oral administration of β-cryptoxanthin (β-CRX), a precursor of vitamin A synthesis, on the transcriptomes of peripheral neutrophils and liver tissue in post-weaned Holstein calves with immature immunity. A single oral administration of β-CRX (0.2 mg/kg body weight) was performed in eight Holstein calves (4.0 ± 0.8 months of age; 117 ± 10 kg) on Day 0. Peripheral neutrophils (n = 4) and liver tissue (n = 4) were collected on Days 0 and 7. Neutrophils were isolated by density gradient centrifugation and treated with the TRIzol reagent. mRNA expression profiles were examined by microarray and differentially expressed genes were investigated using the Ingenuity Pathway Analysis software. The differentially expressed candidate genes identified in neutrophils (COL3A1, DCN, and CCL2) and liver tissue (ACTA1) were involved in enhanced bacterial killing and maintenance of cellular homoeostasis respectively. The changes in the expression of six of the eight common genes encoding enzymes (ADH5 and SQLE) and transcription regulators (RARRES1, COBLL1, RTKN, and HES1) were in the same direction in neutrophils and liver tissue. ADH5 and SQLE are involved in the maintenance of cellular homoeostasis by increasing the availability of substrates, and RARRES1, COBLL1, RTKN, and HES1 are associated with the suppression of apoptosis and carcinogenesis. An in silico analysis revealed that MYC, which is related to the regulation of cellular differentiation and apoptosis, was the most significant upstream regulator in neutrophils and liver tissue. Transcription regulators such as CDKN2A (cell growth suppressor) and SP1 (cell apoptosis enhancer) were significantly inhibited and activated, respectively, in neutrophils and liver tissue. These results suggest that oral administration of β-CRX promotes the expression of candidate genes related to bactericidal ability and regulation of cellular processes in peripheral neutrophils and liver cells in response to the immune-enhancing function of β-CRX in post-weaned Holstein calves.

In-depth systems biological evaluation of bovine alveolar macrophages suggests novel insights into molecular mechanisms underlying Mycobacterium bovis infection

OBJECTIVE

Bovine tuberculosis (bTB) is a chronic respiratory infectious disease of domestic livestock caused by intracellular Mycobacterium bovis infection, which causes ~$3 billion in annual losses to global agriculture. Providing novel tools for bTB managements requires a comprehensive understanding of the molecular regulatory mechanisms underlying the M. bovis infection. Nevertheless, a combination of different bioinformatics and systems biology methods was used in this study in order to clearly understand the molecular regulatory mechanisms of bTB, especially the immunomodulatory mechanisms of M. bovis infection.

METHODS

RNA-seq data were retrieved and processed from 78 (39 non-infected control vs. 39 M. bovis-infected samples) bovine alveolar macrophages (bAMs). Next, weighted gene co-expression network analysis (WGCNA) was performed to identify the co-expression modules in non-infected control bAMs as reference set. The WGCNA module preservation approach was then used to identify non-preserved modules between non-infected controls and M. bovis-infected samples (test set). Additionally, functional enrichment analysis was used to investigate the biological behavior of the non-preserved modules and to identify bTB-specific non-preserved modules. Co-expressed hub genes were identified based on module membership (MM) criteria of WGCNA in the non-preserved modules and then integrated with protein-protein interaction (PPI) networks to identify co-expressed hub genes/transcription factors (TFs) with the highest maximal clique centrality (MCC) score (hub-central genes).

RESULTS

As result, WGCNA analysis led to the identification of 21 modules in the non-infected control bAMs (reference set), among which the topological properties of 14 modules were altered in the M. bovis-infected bAMs (test set). Interestingly, 7 of the 14 non-preserved modules were directly related to the molecular mechanisms underlying the host immune response, immunosuppressive mechanisms of M. bovis, and bTB development. Moreover, among the co-expressed hub genes and TFs of the bTB-specific non-preserved modules, 260 genes/TFs had double centrality in both co-expression and PPI networks and played a crucial role in bAMs-M. bovis interactions. Some of these hub-central genes/TFs, including PSMC4, SRC, BCL2L1, VPS11, MDM2, IRF1, CDKN1A, NLRP3, TLR2, MMP9, ZAP70, LCK, TNF, CCL4, MMP1, CTLA4, ITK, IL6, IL1A, IL1B, CCL20, CD3E, NFKB1, EDN1, STAT1, TIMP1, PTGS2, TNFAIP3, BIRC3, MAPK8, VEGFA, VPS18, ICAM1, TBK1, CTSS, IL10, ACAA1, VPS33B, and HIF1A, had potential targets for inducing immunomodulatory mechanisms by M. bovis to evade the host defense response.

CONCLUSION

The present study provides an in-depth insight into the molecular regulatory mechanisms behind M. bovis infection through biological investigation of the candidate non-preserved modules directly related to bTB development. Furthermore, several hub-central genes/TFs were identified that were significant in determining the fate of M. bovis infection and could be promising targets for developing novel anti-bTB therapies and diagnosis strategies.

Guanylate-binding protein 2b regulates the AMPK/mTOR/ULK1 signalling pathway to induce autophagy during Mycobacterium bovis infection

Autophagic isolation and degradation of intracellular pathogens are employed by host cells as primary innate immune defense mechanisms to control intercellular M. bovis infection. In this study, RNA-Seq technology was used to obtain the total mRNA from bone marrow-derived macrophages (BMDMs) infected with M. bovis at 6 and 24 h after infection. One of the differential genes, GBP2b, was also investigated. Analysis of the significant pathway involved in GBP2b-coexpressed mRNA demonstrated that GBP2b was associated with autophagy and autophagy-related mammalian target of rapamycin (mTOR) signaling and AMP-activated protein kinase (AMPK) signaling. The results of in vivo and in vitro experiments showed significant up-regulation of GBP2b during M. bovis infection. For in vitro validation, small interfering RNA-GBP2b plasmids were transfected into BMDMs and RAW264.7 cells lines to down-regulate the expression of GBP2b. The results showed that the down-regulation of GBP2b impaired autophagy via the AMPK/mTOR/ULK1 pathway, thereby promoting the intracellular survival of M. bovis. Further studies revealed that the activation of AMPK signaling was essential for the regulation of autophagy during M. bovis infection. These findings expand the understanding of how GBP2b regulates autophagy and suggest that GBP2b may be a potential target for the treatment of diseases caused by M. bovis.

Integrated Network Analysis to Identify Key Modules and Potential Hub Genes Involved in Bovine Respiratory Disease: A Systems Biology Approach

Background: Bovine respiratory disease (BRD) is the most common disease in the beef and dairy cattle industry. BRD is a multifactorial disease resulting from the interaction between environmental stressors and infectious agents. However, the molecular mechanisms underlying BRD are not fully understood yet. Therefore, this study aimed to use a systems biology approach to systematically evaluate this disorder to better understand the molecular mechanisms responsible for BRD. Methods: Previously published RNA-seq data from whole blood of 18 healthy and 25 BRD samples were downloaded from the Gene Expression Omnibus (GEO) and then analyzed. Next, two distinct methods of weighted gene coexpression network analysis (WGCNA), i.e., module-trait relationships (MTRs) and module preservation (MP) analysis were used to identify significant highly correlated modules with clinical traits of BRD and non-preserved modules between healthy and BRD samples, respectively. After identifying respective modules by the two mentioned methods of WGCNA, functional enrichment analysis was performed to extract the modules that are biologically related to BRD. Gene coexpression networks based on the hub genes from the candidate modules were then integrated with protein-protein interaction (PPI) networks to identify hub-hub genes and potential transcription factors (TFs). Results: Four significant highly correlated modules with clinical traits of BRD as well as 29 non-preserved modules were identified by MTRs and MP methods, respectively. Among them, two significant highly correlated modules (identified by MTRs) and six nonpreserved modules (identified by MP) were biologically associated with immune response, pulmonary inflammation, and pathogenesis of BRD. After aggregation of gene coexpression networks based on the hub genes with PPI networks, a total of 307 hub-hub genes were identified in the eight candidate modules. Interestingly, most of these hub-hub genes were reported to play an important role in the immune response and BRD pathogenesis. Among the eight candidate modules, the turquoise (identified by MTRs) and purple (identified by MP) modules were highly biologically enriched in BRD. Moreover, STAT1, STAT2, STAT3, IRF7, and IRF9 TFs were suggested to play an important role in the immune system during BRD by regulating the coexpressed genes of these modules. Additionally, a gene set containing several hub-hub genes was identified in the eight candidate modules, such as TLR2, TLR4, IL10, SOCS3, GZMB, ANXA1, ANXA5, PTEN, SGK1, IFI6, ISG15, MX1, MX2, OAS2, IFIH1, DDX58, DHX58, RSAD2, IFI44, IFI44L, EIF2AK2, ISG20, IFIT5, IFITM3, OAS1Y, HERC5, and PRF1, which are potentially critical during infection with agents of bovine respiratory disease complex (BRDC). Conclusion: This study not only helps us to better understand the molecular mechanisms responsible for BRD but also suggested eight candidate modules along with several promising hub-hub genes as diagnosis biomarkers and therapeutic targets for BRD.

Genome-wide association analysis identified both RNA-seq and DNA variants associated to paratuberculosis in Canadian Holstein cattle 'in vitro' experimentally infected macrophages

Background

Mycobacterium avium ssp. paratuberculosis (MAP) is the causative agent of paratuberculosis, or Johne’s disease (JD), an incurable bovine disease. The evidence for susceptibility to MAP disease points to multiple interacting factors, including the genetic predisposition to a dysregulation of the immune system. The endemic situation in cattle populations can be in part explained by a genetic susceptibility to MAP infection. In order to identify the best genetic improvement strategy that will lead to a significant reduction of JD in the population, we need to understand the link between genetic variability and the biological systems that MAP targets in its assault to dominate macrophages. MAP survives in macrophages where it disseminates. We used next-generation RNA (RNA-Seq) sequencing to study of the transcriptome in response to MAP infection of the macrophages from cows that have been naturally infected and identified as positive for JD (JD (+); n = 22) or negative for JD (healthy/resistant, JD (−); n = 28). In addition to identifying genetic variants from RNA-seq data, SNP variants were also identified using the Bovine SNP50 DNA chip.

Results

The complementary strategy allowed the identification of 1,356,248 genetic variants, including 814,168 RNA-seq and 591,220 DNA chip variants. Annotation using SnpEff predicted that the 2435 RNA-seq genetic variants would produce high functional effect on known genes in comparison to the 33 DNA chip variants. Significant variants from JD(+/−) macrophages were identified by genome-wide association study and revealed two quantitative traits loci: BTA4 and 11 at (P < 5 × 10^− 7). Using BovineMine, gene expression levels together with significant genomic variants revealed pathways that potentially influence JD susceptibility, notably the energy-dependent regulation of mTOR by LKB1-AMPK and the metabolism of lipids.

Conclusion

In the present study, we succeeded in identifying genetic variants in regulatory pathways of the macrophages that may affect the susceptibility of cows that are healthy/resistant to MAP infection. RNA-seq provides an unprecedented opportunity to investigate gene expression and to link the genetic variations to biological pathways that MAP normally manipulate during the process of killing macrophages. A strategy incorporating functional markers into genetic selection may have a considerable impact in improving resistance to an incurable disease. Integrating the findings of this research into the conventional genetic selection program may allow faster and more lasting improvement in resistance to bovine paratuberculosis in dairy cattle.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07487-4.

Detection of latent forms of Mycobacterium avium subsp. paratuberculosis infection using host biomarker-based ELISAs greatly improves paratuberculosis diagnostic sensitivity

Bovine paratuberculosis (PTB) is a chronic granulomatous enteritis, caused by Mycobacterium avium subsp. paratuberculosis (MAP), responsible for important economic losses in the dairy industry. Current diagnostic methods have low sensitivities for detection of latent forms of MAP infection, defined by focal granulomatous lesions and scarce humoral response or MAP presence. In contrast, patent infections correspond to multifocal and diffuse types of enteritis where there is increased antibody production, and substantial mycobacterial load. Our previous RNA-Seq analysis allowed the selection of five candidate biomarkers overexpressed in peripheral blood of MAP infected Holstein cows with focal (ABCA13 and MMP8) and diffuse (FAM84A, SPARC and DES) lesions vs. control animals with no detectable PTB-associated lesions in intestine and regional lymph nodes. The aim of the current study was to assess the PTB diagnostic potential of commercial ELISAs designed for the specific detection of these biomarkers. The ability of these ELISAs to identify animals with latent and/or patent forms of MAP infection was investigated using serum from naturally infected cattle (n = 88) and non-infected control animals (n = 67). ROC analysis revealed that the ABCA13-based ELISA showed the highest diagnostic accuracy for the detection of infected animals with focal lesions (AUC 0.837, sensitivity 79.25% and specificity 88.06%) and with any type of histological lesion (AUC 0.793, sensitivity 69.41% and specificity 86.57%) improving on the diagnostic performance of the popular IDEXX ELISA and other conventional diagnostic methods. SPARC and MMP8 showed the highest diagnostic accuracy for the detection of animals with multifocal (AUC 0.852) and diffuse lesions (AUC 0.831), respectively. In conclusion, our results suggest that quantification of ABCA13, SPARC and MMP8 by ELISA has the potential for implementation as a diagnostic tool to reliably identify MAP infection, greatly improving early detection of MAP latent infections when antibody responses and fecal shedding are undetectable using conventional diagnostic methods.

RNA-Seq analysis of ileocecal valve and peripheral blood from Holstein cattle infected with Mycobacterium avium subsp. paratuberculosis revealed dysregulation of the CXCL8/IL8 signaling pathway

Paratuberculosis is chronic granulomatous enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Whole RNA-sequencing (RNA-Seq) is a promising source of novel biomarkers for early MAP infection and disease progression in cattle. Since the blood transcriptome is widely used as a source of biomarkers, we analyzed whether it recapitulates, at least in part, the transcriptome of the ileocecal valve (ICV), the primary site of MAP colonization. Total RNA was prepared from peripheral blood (PB) and ICV samples, and RNA-Seq was used to compare gene expression between animals with focal or diffuse histopathological lesions in gut tissues versus control animals with no detectable signs of infection. Our results demonstrated both shared, and PB and ICV-specific gene expression in response to a natural MAP infection. As expected, the number of differentially expressed (DE) genes was larger in the ICV than in the PB samples. Among the DE genes in the PB and ICV samples, there were some common genes irrespective of the type of lesion including the C-X-C motif chemokine ligand 8 (CXCL8/IL8), apolipoprotein L (APOLD1), and the interferon inducible protein 27 (IFI27). The biological processes (BP) enriched in the PB gene expression profiles from the cows with diffuse lesions included the killing of cells of other organism, defense response, immune response and the regulation of neutrophil chemotaxis. Two of these BP, the defense and immune response, were also enriched in the ICV from the cows with diffuse lesions. Metabolic analysis of the DE genes revealed that the N-glycan biosynthesis, bile secretion, one-carbon pool by folate and purine metabolism were significantly enriched in the ICV from the cows with focal lesions. In the ICV from cows with diffuse lesions; the valine, leucine and isoleucine degradation route, purine metabolism, vitamin digestion and absorption and the cholesterol routes were enriched. Some of the identified DE genes, BP and metabolic pathways will be studied further to develop novel diagnostic tools, vaccines and immunotherapeutics.

Kallikrein 12 Regulates Innate Resistance of Murine Macrophages against Mycobacterium bovis Infection by Modulating Autophagy and Apoptosis

Mycobacterium bovis (M. bovis) is a member of the Mycobacterium tuberculosis (Mtb) complex causing bovine tuberculosis (TB) and imposing a high zoonotic threat to human health. Kallikreins (KLKs) belong to a subgroup of secreted serine proteases. As their role is established in various physiological and pathological processes, it is likely that KLKs expression may mediate a host immune response against the M. bovis infection. In the current study, we report in vivo and in vitro upregulation of KLK12 in the M. bovis infection. To define the role of KLK12 in immune response regulation of murine macrophages, we produced KLK12 knockdown bone marrow derived macrophages (BMDMs) by using siRNA transfection. Interestingly, the knockdown of KLK12 resulted in a significant downregulation of autophagy and apoptosis in M. bovis infected BMDMs. Furthermore, we demonstrated that this KLK12 mediated regulation of autophagy and apoptosis involves mTOR/AMPK/TSC2 and BAX/Bcl-2/Cytochrome c/Caspase 3 pathways, respectively. Similarly, inflammatory cytokines IL-1β, IL-6, IL-12 and TNF-α were significantly downregulated in KLK12 knockdown macrophages but the difference in IL-10 and IFN-β expression was non-significant. Taken together, these findings suggest that upregulation of KLK12 in M. bovis infected murine macrophages plays a substantial role in the protective immune response regulation by modulating autophagy, apoptosis and pro-inflammatory pathways. To our knowledge, this is the first report on expression and the role of KLK12 in the M. bovis infection and the data may contribute to a new paradigm for diagnosis and treatment of bovine TB.

Increased Expression of miR-483-3p Impairs the Vascular Response to Injury in Type 2 Diabetes

Aggravated endothelial injury and impaired endothelial repair capacity contribute to the high cardiovascular risk in patients with type 2 diabetes (T2D), but the underlying mechanisms are still incompletely understood. Here we describe the functional role of a mature form of miRNA (miR) 483-3p, which limits endothelial repair capacity in patients with T2D. Expression of human (hsa)-miR-483-3p was higher in endothelial-supportive M2-type macrophages (M2MΦs) and in the aortic wall of patients with T2D than in control subjects without diabetes. Likewise, the murine (mmu)-miR-483* was higher in T2D than in nondiabetic murine carotid samples. Overexpression of miR-483-3p increased endothelial and macrophage apoptosis and impaired reendothelialization in vitro. The inhibition of hsa-miR-483-3p in human T2D M2MΦs transplanted to athymic nude mice (NMRI-Foxn1^ν/Foxn1^ν ) or systemic inhibition of mmu-miR-483* in B6.BKS(D)-Lepr^db /J diabetic mice rescued diabetes-associated impairment of reendothelialization in the murine carotid-injury model. We identified the endothelial transcription factor vascular endothelial zinc finger 1 (VEZF1) as a direct target of miR-483-3p. VEZF1 expression was reduced in aortae of diabetic mice and upregulated in diabetic murine aortae upon systemic inhibition of mmu-483*. The miRNA miR-483-3p is a critical regulator of endothelial integrity in patients with T2D and may represent a therapeutic target to rescue endothelial regeneration after injury in patients with T2D.

Genome-wide transcriptional profiling identifies potential signatures in discriminating active tuberculosis from latent infection

To better understand the host immune response involved in the progression from latent tuberculosis infection (LTBI) to active tuberculosis (TB) and identify the potential signatures for discriminating TB from LTBI, we performed a genome-wide transcriptional profile of Mycobacterium tuberculosis (M.TB)–specific antigens-stimulated peripheral blood mononuclear cells (PBMCs) from patients with TB, LTBI individuals and healthy controls (HCs). A total of 209 and 234 differentially expressed genes were detected in TB vs. LTBI and TB vs. HCs, respectively. Nineteen differentially expressed genes with top fold change between TB and the other 2 groups were validated using quantitative real-time PCR (qPCR), and showed 94.7% consistent expression pattern with microarray test. Six genes were selected for further validation in an independent sample set of 230 samples. Expression of the resistin (RETN) and kallikrein 1 (KLK1) genes showed the greatest difference between the TB and LTBI or HC groups (P < 0.0001). Receiver operating characteristic curve (ROC) analysis showed that the areas under the curve (AUC) for RETN and KLK1 were 0.844 (0.783–0.904) and 0.833 (0.769–0.897), respectively, when discriminating TB from LTBI. The combination of these two genes achieved the best discriminative capacity [AUC = 0.916 (0.872–0.961)], with a sensitivity of 71.2% (58.7%–81.7%) and a specificity of 93.6% (85.7%–97.9%). Our results provide a new potentially diagnostic signature for discriminating TB and LTBI and have important implications for better understanding the pathogenesis involved in the transition from latent infection to TB activation.

Differential gene expression in Mycobacterium bovis challenged monocyte-derived macrophages of cattle

A functional genomics approach was used to examine the immune response for transcriptional profiling of PBMC M. bovis infected cattle and healthy control cattle to stimulation with bovine tuberculin (purified protein derivative PPD-b). Total cellular RNA was extracted from non-challenged control and M. bovis challenged MDM for all animals at intervals of 6 h post-challenge, in response to in-vitro challenge with M. bovis (multiplicity of infection 2:1) and prepared for global gene expression analysis using the Agilent Bovine (V2) Gene Expression Microarray, 8 × 60 K. The pattern of expression of these genes in PPD bovine stimulated PBMC provides the first description of an M. bovis specific signature of infection that may provide insights into the molecular basis of the host response to infection. Analysis of these mapped reads showed 2450 genes (1291 up regulated and 1158 down regulated) 462 putative natural antisense transcripts (354 up-regulated and 108 down regulated) that were differentially expressed based on sense and antisense strand data, respectively (adjusted P-value ≤ 0.05). The results provided enrichment for genes involved top ten up regulated and down regulated panel of genes, including transcription factors proliferation of T and B lymphocytes. The highest differentially-expressed genes were associated to immune and inflammatory responses, immunity, differentiation, cell growth, apoptosis, cellular trafficking and regulation of lipolysis and thermogenesis. Microarray results were confirmed in infected cattle by RT qPCR to identify potential biomarkers TLR2, CD80, NFKB1, IL8, CXCL6 and ADORA3 of bovine tuberculosis.

Johne's disease in cattle: an in vitro model to study early response to infection of Mycobacterium avium subsp. paratuberculosis using RNA-seq

Johne's disease is a chronic granulomatous enteritis caused by Mycobacterium avium subsp. paratubercolosis (MAP) which affects ruminants worldwide and has a significant economic impact. MAP has also been associated with human Crohn's disease, although this connection is not well established. MAP is highly adapted for survival within host macrophages and prevents macrophage activation, blocks phagosome acidification and maturation, and attenuates presentation of antigens to the immune system. The consequence is a very long silent infection before clinical signs are observed. The present work examined the transcriptome of bovine monocyte-derived macrophages (MDM) infected with the L1 strain of MAP at 2h, 6h and 24h post infection using RNA-seq. Pathway over-representation analysis of genes differentially expressed between infected vs. control MDM identified that immune related pathways were affected. Genes belonging to the cytokine-cytokine receptor interaction pathway and members of the JAK-STAT pathway, which is involved in the regulation of immune response, were up-regulated. However, in parallel inhibitors of immune functions were activated, including suppressor of cytokine signaling (SOCS) and cytokine-inducible SH2-containing protein (CISH), which most likely suppresses IFNγ and the JAK/STAT signaling cascade in infected MDM, which may favour MAP survival. After exposure, macrophages phagocytise pathogens, activate the complement cascade and the adaptive immune system through the antigen presentation process. However, data presented here suggest that genes related to phagocytosis and lysosome function are down regulated in MAP infected MDM. Genes of MHC class II and complement pathway were also down-regulated. This study therefore shows that MAP infection is associated with changes in expression of genes related to the host immune response that may affect its ability to survive and multiply inside the host cell.

Sp110 enhances macrophage resistance to Mycobacterium tuberculosis via inducing endoplasmic reticulum stress and inhibiting anti-apoptotic factors

Tuberculosis remains a leading health problem worldwide and still accounts for about 1.3 million deaths annually. Expression of the mouse Sp110 nuclear body protein (Sp110) upregulates the apoptotic pathway, which plays an essential role in enhancing host immunity to Mycobacterium tuberculosis (Mtb). However, the mechanism of this upregulation is unclear. Here, we have identified 253 proteins in mouse macrophages that interact with Sp110, of which 251 proteins were previously uncharacterized. The results showed that Sp110 interacts with heat shock protein 5 (Hspa5) to activate endoplasmic reticulum (ER) stress-induced apoptosis, and that this is essential for Sp110 enhanced macrophage resistance to Mtb. Inhibition of the ER stress pathway abolishing the Sp110-enhanced macrophage apoptosis and resulted in increased intracellular survival of Mtb in macrophages overexpressing Sp110 Further studies revealed that Sp110 also interacts with the RNA binding protein, Ncl to promote its degradation. Consequently, the expression of Bcl2, usually stabilized by Ncl, was downregulated in Sp110 overexpressing macrophages. Moreover, overexpression of Sp110 promotes degradation of ribosomal protein Rps3a, resulting in upregulation of the activity of the pro-apoptotic poly (ADP-ribose) polymerase (PARP). In addition, macrophages from transgenic cattle with increased Sp110 expression confirmed that activation of the ER stress response is the main pathway through which Sp110-enhanced macrophages impart resistance to Mtb. This work has revealed the mechanism of Sp110 enhanced macrophage apoptosis in response to Mtb infection, and provides new insights into the study of host-pathogen interactions.

Divergent macrophage responses to Mycobacterium bovis among naturally exposed uninfected and infected cattle

Mycobacterium bovis, the causative agent of bovine tuberculosis (TB), is a successful pathogen that remains an important global threat to livestock. Cattle naturally exposed to M. bovis normally become reactive to the M. bovis-purified protein derivative (tuberculin) skin test; however, some individuals remain negative, suggesting that they may be resistant to infection. To better understand host innate resistance to infection, 26 cattle from herds with a long history of high TB prevalence were included in this study. We investigated the bactericidal activity, the production of reactive oxygen and nitrogen species and the TB-related gene expression profile after in vitro M. bovis challenge of monocyte-derived macrophages from cattle with TB (n=17) and from non-infected, exposed cattle (in-contacts, n=9). The disease status was established based on the tuberculin skin test and blood interferon-gamma test responses, the presence of visible lesions at inspection on abattoirs and the histopathology and culture of M. bovis. Although macrophages from TB-infected cattle enabled M. bovis replication, macrophages from healthy, exposed cattle had twofold lower bacterial loads, overproduced nitric oxide and had lower interleukin (IL)-10 gene expression (P⩽0.05). Higher mRNA expression levels of inducible nitric oxide synthase, C-C motif chemokine ligand 2 and IL-12 were observed in macrophages from all in-contact cattle than in macrophages from their TB-infected counterparts, which expressed more tumour necrosis factor-α; however, the differences were not statistically significant owing to individual variation. These results confirm that macrophage bactericidal responses have a crucial role in innate resistance to M. bovis infection in cattle.

The Transcriptional Foundations of Sp110-mediated Macrophage (RAW264.7) Resistance to Mycobacterium tuberculosis H37Ra

Human tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a leading global health problem, causing 1.3 million deaths each year. The nuclear body protein, Sp110, has been linked to TB resistance and previous work showed that it enhances macrophage apoptosis upon Mtb infection. Here, we report on the role of Sp110 in transcriptional regulation of macrophage responses to Mtb through integrated transcriptome and mechanistic studies. Transcriptome analysis revealed that Sp110 regulates genes involved in immune responses, apoptosis, defence responses, and inflammatory responses. Detailed investigation revealed that, in addition to apoptosis-related genes, Sp110 regulates cytokines, chemokines and genes that regulate intracellular survival of Mtb. Moreover, Sp110 regulates miRNA expression in macrophages, with immune and apoptosis-related miRNAs such as miR-125a, miR-146a, miR-155, miR-21a and miR-99b under Sp110 regulation. Additionally, our results showed that Sp110 upregulates BCL2 modifying factor (Bmf) by inhibiting miR-125a, and forced expression of Bmf induces macrophage apoptosis. These findings not only reveal the transcriptional basis of Sp110-mediated macrophage resistance to Mtb, but also suggest potential regulatory roles for Sp110 related to inflammatory responses, miRNA profiles, and the intracellular growth of Mtb.