Syndecans promote mycobacterial internalization by lung epithelial cells

Pulmonary tuberculosis (TB) is an airborne disease caused by the intracellular bacterial pathogen Mycobacterium tuberculosis (Mtb). Alveolar epithelial cells and macrophages are the first point of contact for Mtb in the respiratory tract. However, the mechanisms of mycobacterial attachment to, and internalization by, nonprofessional phagocytes, such as epithelial cells, remain incompletely understood. We identified syndecan 4 (Sdc4) as mycobacterial attachment receptor on alveolar epithelial cells. Sdc4 mRNA expression was increased in human and mouse alveolar epithelial cells after mycobacterial infection. Sdc4 knockdown in alveolar epithelial cells or blocking with anti‐Sdc4 antibody reduced mycobacterial attachment and internalization. At the molecular level, interactions between epithelial cells and mycobacteria involved host Sdc and the mycobacterial heparin‐binding hemagglutinin adhesin. In vivo, Sdc1/Sdc4 double‐knockout mice were more resistant to Mtb colonization of the lung. Our work reveals a role for distinct Sdcs in promoting mycobacterial entry into alveolar epithelial cells with impact on outcome of TB disease.     

Serodiagnosis of environmental mycobacterial infections

To demonstrate the usefulness of enzyme-linked immunosorbent assay for serodiagnosis of mycobacterioses due to environmental mycobacteria we utilized a panel of glycolipid antigens selective for Mycobacterium avium-intracellulare, Mycobacterium kansasii, Mycobacterium xenopi, Mycobacterium scrofulaceum and Mycobacterium gordonae. The levels of circulating antibodies were determined against the environmental mycobacteria, and Mycobacterium tuberculosis in human immunodeficiency virus-negative and -positive patient sera. The method used immunomagnetic separation of the antigens, with covalent immobilization of antibodies to superparamagnetic amine and carboxyl terminated particles in solutions of the specific antigens. Enzyme-linked immunosorbent assay was performed on 195 patient sera: 34 with infections due to environmental mycobacteria, 114 with tuberculosis, 47 with other respiratory diseases. There were 46 human immunodeficiency virus-1 infected individuals. Among the 34 infections due to environmental mycobacteria, 9 patients were singularly infected with an environmental mycobacterium, and 25 co-infected with both M. tuberculosis and an environmental mycobacterium. Sensitivity, specificity and false positivity ranges were determined for each of the volunteer groups: tuberculosis positive, human immunodeficiency virus negative; tuberculosis positive, human immunodeficiency virus positive; those with infections due to individual environmental mycobacteria (such as M. scrofulaceum and M. kansasii); and those with other respiratory diseases. We demonstrate that such multiple assays, can be useful for the early diagnosis of diverse environmental mycobacterial infections to allow the start of treatment earlier than henceforth.     

MicroRNA‐495‐3p diminishes doxorubicin‐induced cardiotoxicity through activating AKT

Doxorubicin (Dox) is a broad‐spectrum antitumour agent; however, its clinical application is impeded due to the cumulative cardiotoxicity. The present study aims to investigate the role and underlying mechanisms of microRNA‐495‐3p (miR‐495‐3p) in Dox‐induced cardiotoxicity. Herein, we found that cardiac miR‐495‐3p expression was significantly decreased in Dox‐treated hearts, and that the miR‐495‐3p agomir could prevent oxidative stress, cell apoptosis, cardiac mass loss, fibrosis and cardiac dysfunction upon Dox stimulation. In contrast, the miR‐495‐3p antagomir dramatically aggravated Dox‐induced cardiotoxicity in mice. Besides, we found that the miR‐495‐3p agomir attenuated, while the miR‐495‐3p antagomir exacerbated Dox‐induced oxidative stress and cellular injury in vitro. Mechanistically, we demonstrated that miR‐495‐3p directly bound to the 3′‐untranslational region of phosphate and tension homology deleted on chromosome ten (PTEN), downregulated PTEN expression and subsequently activated protein kinase B (PKB/AKT) pathway, and that PTEN overexpression or AKT inhibition completely abolished the cardioprotective effects of the miR‐495‐3p agomir. Our study for the first time identify miR‐495‐3p as an endogenous protectant against Dox‐induced cardiotoxicity through activating AKT pathway in vivo and in vitro.     

Mycobacterium tuberculosis protein kinase G acts as an unusual ubiquitinating enzyme to impair host immunity

Upon Mycobacterium tuberculosis (Mtb) infection, protein kinase G (PknG), a eukaryotic‐type serine‐threonine protein kinase (STPK), is secreted into host macrophages to promote intracellular survival of the pathogen. However, the mechanisms underlying this PknG–host interaction remain unclear. Here, we demonstrate that PknG serves both as a ubiquitin‐activating enzyme (E1) and a ubiquitin ligase (E3) to trigger the ubiquitination and degradation of tumor necrosis factor receptor‐associated factor 2 (TRAF2) and TGF‐β‐activated kinase 1 (TAK1), thereby inhibiting the activation of NF‐κB signaling and host innate responses. PknG promotes the attachment of ubiquitin (Ub) to the ubiquitin‐conjugating enzyme (E2) UbcH7 via an isopeptide bond (UbcH7 K82‐Ub), rather than the usual C86‐Ub thiol‐ester bond. PknG induces the discharge of Ub from UbcH7 by acting as an isopeptidase, before attaching Ub to its substrates. These results demonstrate that PknG acts as an unusual ubiquitinating enzyme to remove key components of the innate immunity system, thus providing a potential target for tuberculosis treatment.     

The PAX5‐JAK2 translocation acts as dual‐hit mutation that promotes aggressive B‐cell leukemia via nuclear STAT5 activation

While PAX5 is an important tumor suppressor gene in B‐cell acute lymphoblastic leukemia (B‐ALL), it is also involved in oncogenic translocations coding for diverse PAX5 fusion proteins. PAX5‐JAK2 encodes a protein consisting of the PAX5 DNA‐binding region fused to the constitutively active JAK2 kinase domain. Here, we studied the oncogenic function of the PAX5‐JAK2 fusion protein in a mouse model expressing it from the endogenous Pax5 locus, resulting in inactivation of one of the two Pax5 alleles. Pax5 ^Jak2/+ mice rapidly developed an aggressive B‐ALL in the absence of another cooperating exogenous gene mutation. The DNA‐binding function and kinase activity of Pax5‐Jak2 as well as IL‐7 signaling contributed to leukemia development. Interestingly, all Pax5 ^Jak2/+ tumors lost the remaining wild‐type Pax5 allele, allowing efficient DNA‐binding of Pax5‐Jak2. While we could not find evidence for a nuclear role of Pax5‐Jak2 as an epigenetic regulator, high levels of active phosphorylated STAT5 and increased expression of STAT5 target genes were seen in Pax5 ^Jak2/+ B‐ALL tumors, implying that nuclear Pax5‐Jak2 phosphorylates STAT5. Together, these data reveal Pax5‐Jak2 as an important nuclear driver of leukemogenesis by maintaining phosphorylated STAT5 levels in the nucleus.     

MiR‐223‐3p inhibits rTp17‐induced inflammasome activation and pyroptosis by targeting NLRP3

The incidence of syphilis caused by Treponema pallidum subsp pallidum (T pallidum) infection is accompanied by inflammatory injuries of vascular endothelial cells. Studies have revealed that T pallidum infection could induce inflammasome activation and pyroptosis in macrophages. MicroRNA‐223‐3p (miR‐223‐3p) was reported to be a negative regulator in inflammatory diseases. The present study aimed to explore whether miR‐223‐3p regulates T pallidum‐induced inflammasome activation and pyroptosis in vascular endothelial cells, and determine the mechanisms which underlie this process. MiR‐223‐3p levels in syphilis and control samples were determined. The biological function of miR‐223‐3p in the NLRP3 inflammasome and pyroptosis was evaluated in T pallidum‐infected human umbilical vein endothelial cells (HUVECs). We observed a dramatic decrease in miR‐223‐3p levels in syphilis patients (n = 20) when compared to healthy controls (n = 20). Moreover, miR‐223‐3p showed a notable inhibitory effect on recombinant Tp17 (rTP17)‐induced caspase‐1 activation, resulting in decrease in IL‐1β production and pyroptosis, which was accompanied by the release of lactate dehydrogenase (LDH) in HUVECs. Additionally, the dual‐luciferase assay confirmed that NLRP3 is a direct target of miR‐223‐3p. Moreover, NLRP3 overexpression or knockdown largely blocked the effects of miR‐223‐3p on T pallidum‐induced inflammasome activation and pyroptosis in HUVECs. Most importantly, a notable negative correlation was observed between miR‐223‐3p and NLRP3, caspase‐1, and IL‐1β, respectively, in the serum of syphilis patients and healthy controls. Taken together, our results reveal that miR‐223‐3p targets NLRP3 to suppress inflammasome activation and pyroptosis in T pallidum‐infected endothelial cells, implying that miR‐223‐3p could be a potential target for syphilis patients.     

m6A‐mediated alternative splicing coupled with nonsense‐mediated mRNA decay regulates SAM synthetase homeostasis

Alternative splicing of pre‐mRNAs can regulate gene expression levels by coupling with nonsense‐mediated mRNA decay (NMD). In order to elucidate a repertoire of mRNAs regulated by alternative splicing coupled with NMD (AS‐NMD) in an organism, we performed long‐read RNA sequencing of poly(A)⁺ RNAs from an NMD‐deficient mutant strain of Caenorhabditis elegans, and obtained full‐length sequences for mRNA isoforms from 259 high‐confidence AS‐NMD genes. Among them are the S‐adenosyl‐L‐methionine (SAM) synthetase (sams) genes sams‐3 and sams‐4. SAM synthetase activity autoregulates sams gene expression through AS‐NMD in a negative feedback loop. We furthermore find that METT‐10, the orthologue of human U6 snRNA methyltransferase METTL16, is required for the splicing regulation in␣vivo, and specifically methylates the invariant AG dinucleotide at the distal 3′ splice site (3′SS) in␣vitro. Direct RNA sequencing coupled with machine learning confirms m⁶A modification of endogenous sams mRNAs. Overall, these results indicate that homeostasis of SAM synthetase in C. elegans is maintained by alternative splicing regulation through m⁶A modification at the 3′SS of the sams genes.     

Up‐regulated SAMD9L modulated by TLR2 and HIF‐1α as a promising biomarker in tuberculosis

The aim of this study was to identify potential biomarkers of TB in blood and determine their function in Mtb‐infected macrophages. First of all, WGCNA was used to analyse 9451 genes with significant changes in TB patients’ whole blood. The 220 interferon‐γ‐related genes were identified, and then 30 key genes were screened using Cytoscape. Then, the AUC values of key genes were calculated to further narrow the gene range. Finally, we identified 9 genes from {"type":"entrez-geo","attrs":{"text":"GSE19444","term_id":"19444"}}GSE19444. ROC analysis showed that SAMD9L, among 9 genes, had a high diagnostic value (AUC = 0.925) and a differential diagnostic value (AUC>0.865). To further narrow down the range of DEGs, the top 10 hub‐connecting genes were screened from monocytes ({"type":"entrez-geo","attrs":{"text":"GSE19443","term_id":"19443"}}GSE19443). Finally, we obtained 4 genes (SAMD9L, GBP1, GBP5 and STAT1) by intersections of genes from monocytes and whole blood. Among them, it was found that the function of SAMD9L was unknown after data review, so this paper studied this gene. Our results showed that SAMD9L is up‐regulated and suppresses cell necrosis, and might be regulated by TLR2 and HIF‐1α during Mtb infection. In addition, miR‐181b‐5p is significantly up‐regulated in the peripheral blood plasma of tuberculosis patients, which has a high diagnostic value (AUC = 0.969).     

Characterization of an aminotransferase from Acanthamoeba polyphaga Mimivirus

Acanthamoeba polyphaga Mimivirus, a complex virus that infects amoeba, was first reported in 2003. It is now known that its DNA genome encodes for nearly 1,000 proteins including enzymes that are required for the biosynthesis of the unusual sugar 4‐amino‐4,6‐dideoxy‐d‐glucose, also known as d‐viosamine. As observed in some bacteria, the pathway for the production of this sugar initiates with a nucleotide‐linked sugar, which in the Mimivirus is thought to be UDP‐d‐glucose. The enzyme required for the installment of the amino group at the C‐4′ position of the pyranosyl moiety is encoded in the Mimivirus by the L136 gene. Here, we describe a structural and functional analysis of this pyridoxal 5′‐phosphate‐dependent enzyme, referred to as L136. For this analysis, three high‐resolution X‐ray structures were determined: the wildtype enzyme/pyridoxamine 5′‐phosphate/dTDP complex and the site‐directed mutant variant K185A in the presence of either UDP‐4‐amino‐4,6‐dideoxy‐d‐glucose or dTDP‐4‐amino‐4,6‐dideoxy‐d‐glucose. Additionally, the kinetic parameters of the enzyme utilizing either UDP‐d‐glucose or dTDP‐d‐glucose were measured and demonstrated that L136 is efficient with both substrates. This is in sharp contrast to the structurally related DesI from Streptomyces venezuelae, whose three‐dimensional architecture was previously reported by this laboratory. As determined in this investigation,DesI shows a profound preference in its catalytic efficiency for the dTDP‐linked sugar substrate. This difference can be explained in part by a hydrophobic patch in DesI that is missing in L136. Notably, the structure of L136 reported here represents the first three‐dimensional model for a virally encoded PLP‐dependent enzyme and thus provides new information on sugar aminotransferases in general.     

Biosynthesis of (R)‐(+)‐perillyl alcohol by Escherichia coli expressing neryl pyrophosphate synthase

(R)‐(+)‐perillyl alcohol is widely used in agricultural and anticarcinogenic fields. Microbial production of (R)‐(+)‐perillyl alcohol was investigated in this study. We optimized biosynthesis of (R)‐(+)‐perillyl alcohol in Escherichia coli by using neryl pyrophosphate synthase and NADPH regeneration. Engineering neryl pyrophosphate (NPP)‐supplied pathway resulted in a 4‐fold improvement of (R)‐(+)‐perillyl alcohol titer. Subsequently, combined engineering of p‐cymene monooxygenase (CymA) expression and module for NADPH regeneration exhibited a 15.4‐fold increase of titer over the initial strain S02. Finally, 453 mg/L (R)‐(+)‐perillyl alcohol was achieved in fed‐batch fermentation, which is the highest (R)‐(+)‐perillyl alcohol titer in E. coli.     

Cask methylation involved in the injury of insulin secretion function caused by interleukin1‐β

Islet inflammation severely impairs pancreatic β‐cell function, but the specific mechanisms are still unclear. Interleukin1‐β (IL‐1β), an essential inflammatory factor, exerts a vital role in multiple physio‐pathologic processes, including diabetes. Calcium/calmodulin‐dependent serine protein kinase (CASK) is an important regulator especially in insulin secretion process. This study aims to unveil the function of CASK in IL‐1β–induced insulin secretion dysfunction and the possible mechanism thereof. Islets of Sprague‐Dawley (SD) rats and INS‐1 cells stimulated with IL‐1β were utilized as models of chronic inflammation. Insulin secretion function associated with Cask and DNA methyltransferases (DNMT) expression were assessed. The possible mechanisms of IL‐1β‐induced pancreatic β‐cell dysfunction were also explored. In this study, CASK overexpression effectively improved IL‐1β‐induced islet β‐cells dysfunction, increased insulin secretion. DNA methyltransferases and the level of methylation in the promoter region of Cask were elevated after IL‐1β administration. Methyltransferase inhibitor 5‐Aza‐2’‐deoxycytidine (5‐Aza‐dC) and si‐DNMTs partially up‐regulated CASK expression and reversed potassium stimulated insulin secretion (KSIS) and glucose‐stimulated insulin secretion (GSIS) function under IL‐1β treatment in INS‐1 and rat islets. These results reveal a previously unknown effect of IL‐1β on insulin secretion dysfunction and demonstrate a novel pathway for Cask silencing based on activation of DNA methyltransferases via inducible nitric oxide synthase (iNOS) and modification of gene promoter methylation.     

PknG supports mycobacterial adaptation in acidic environment

Mycobacterium tuberculosis (Mtb), causative agent of human tuberculosis (TB), has the remarkable ability to adapt to the hostile environment inside host cells. Eleven eukaryotic like serine-threonine protein kinases (STPKs) are present in Mtb. Protein kinase G (PknG) has been shown to promote mycobacterial survival inside host cells. A homolog of PknG is also present in Mycobacterium smegmatis (MS), a fast grower, non-pathogenic mycobacterium. In the present study, we have analyzed the role of PknG in mycobacteria during exposure to acidic environment. Expression of pknG in MS was decreased in acidic medium. Recombinant MS ectopically expressing pknG (MS-G) showed higher growth in acidic medium compared to wild type counterpart. MS-G also showed higher resistance upon exposure to 3.0 pH and better adaptability to acidic pH. Western blot analysis showed differential threonine but not serine phosphorylation of cellular proteins in MS at acidic pH which was restored by ectopic expression of pknG in MS. In Mtb H37Ra (Mtb-Ra), expression of pknG was increased at acidic pH. We also observed decreased expression of pknG in MS during infection in macrophages while the expression of pknG in Mtb-Ra was increased in similar conditions. Taken together, our data strongly suggests that pknG regulates growth of mycobacteria in acidic environment and is differentially transcribed in MS and Mtb under these conditions.     

LOXL1‐AS1 communicating with TIAR modulates vasculogenic mimicry in glioma via regulation of the miR‐374b‐5p/MMP14 axis

At present, growing evidence indicates that long non‐coding RNAs (lncRNAs) participate in the progression of glioma. The function of LOXL1‐AS1 in vasculogenic mimicry (VM) in glioma remains unclear. First, the expressions of TIAR, the lncRNA LOXL1‐AS1, miR‐374b‐5p and MMP14 were examined by qRT‐PCR and Western blot in both, glioma tissues and glioma cell lines. Proliferation, migration, invasion and tube formation assays were conducted to evaluate the roles of TIAR, LOXL1‐AS1, miR‐374b‐5p and MMP14 in malignant cellular behaviours in glioma cells. A nude mouse xenograft model and dual staining for CD34 and PAS were used to assess whether VM was affected by TIAR, LOXL1‐AS1 or miR‐374b‐5p in vivo. In this study, low levels of TIAR and high levels of LOXL1‐AS1 were found in glioma cells and tissues. TIAR downregulated the expression of LOXL1‐AS1 by destabilizing it. LOXL1‐AS1 acted like a miRNA sponge towards miR‐374b‐5p so that downregulation of the former greatly inhibited cell proliferation, migration, invasion and VM. Additionally, miR‐374b‐5p overexpression repressed malignant biological behaviours and VM in glioma by modifying MMP14. In summary, we demonstrated that TIAR combined with LOXL1‐AS1 modulates VM in glioma via the miR‐374b‐5p/MMP14 axis, revealing novel targets for glioma therapy.     

Mycobacterium tuberculosis: the honey badger of pathogens

Mycobacterium tuberculosis is a fascinating object of study: it is one of the deadliest pathogens of humankind, able to fend off persistent attacks by the immune system or drugs Subject Categories: Immunology, Microbiology, Virology & Host Pathogen Interaction, Chemical Biology

I have always been interested in infectious diseases since I began to study biology. As a graduate student, my pathogen of choice was Salmonella typhimurium, which typically causes diarrhea that can potentially lead to death. Salmonella''s rapid doubling time, and the availability of elegant genetic tools, a wealth of reagents, and a robust animal infection model put this bug at the apex of ideal host–pathogen systems to study. After I finished my PhD studies—and for reasons to be told another day—my career took an unexpected detour into an area of research I never thought I would be interested in: I went from the sublime to the ridiculous, from Salmonella to Mycobacterium tuberculosis (Mtb), an excruciatingly slow‐growing bacillus with few genetic tools, a paucity of reagents, and an animal model in which an experiment can take a year or longer. Having said all of that, I love working on this pathogen.For those of you who do not know much about Mtb, it is the world''s deadliest bacterium that causes the disease tuberculosis (TB). As Mtb is spread in aerosol droplets coughed up by infected individuals, TB is highly contagious, and about one‐third of the world''s population may be infected with Mtb, although this number has been reasonably challenged (Behr et al, 2021). Even if the numbers of latent or asymptomatic infections are debated, there are some back‐of‐the‐envelope estimates that Mtb has killed more than a billion humans over the millennia. Although TB is often treatable with antibiotics and most Mtb‐infected healthy individuals are asymptomatic, the appearance of multi‐drug‐resistant Mtb and HIV/AIDS has further increased the number of deaths caused by this pathogen.How has Mtb become such a successful pathogen? For one, we lack an effective vaccine to prevent infection. Many readers may point out that they have themselves been given a TB vaccine; known as “BCG” for bacille Calmette–Guérin, this is a laboratory‐attenuated strain of a species related to Mtb called Mycobacterium bovis. While BCG does provide some protection for children against TB, BCG is essentially ineffective against pulmonary TB in adults. For this reason, it is not used in the USA and many other countries.Another major challenge to treating TB has been a lack of antimicrobials that can access Mtb bacilli in privileged sites known as granulomas, which are cell‐fortified structures our immune system builds to contain microbial growth. In addition to the granuloma walls, Mtb has a highly complex cell envelope that protects it from many small molecules. I imagine that antimicrobial molecules have the challenging task of reaching an enemy shielded in armor, hiding deep inside a castle keep, and surrounded by a vast moat, and an army of orcs.On top of these therapeutic barriers, most antimicrobials work on metabolically active or growing bacteria. Mtb, however, grows very slowly, with a doubling time under optimal laboratory conditions of about 20 h—compared with 20 min for Salmonella. Moreover, Mtb is believed to enter a “persistent” or “latent” state in its natural host with limited cell divisions. This extremely slow growth makes treatment a long and tedious prospect: 6–12 months of antibiotic treatment are generally required, during which time one cannot drink alcohol due to the potential liver toxicity of the drugs. Believe it or not, there are people who would rather refuse TB treatment than give up alcohol for a few months. Additionally, the perception of “feeling cured” after a few weeks of TB therapy can also lead to a lapse in compliance. The consequence of failing to clear a partially treated infection is the emergence of drug resistance, which has created strains that are extensively resistant to most frontline TB drugs.When thinking about the difficulty of curing Mtb infections, I am reminded of the fierce and fearless honey badger, which came to fame through a viral YouTube video. The narrator points out how honey badgers “don''t care” about battling vicious predators in order to get food: venomous snakes, stinging bees—you name it. I once saw a photo of a honey badger that looked more like a pin cushion, harpooned with numerous porcupine quills. This battle royale of the wilderness is a perfect analogy of Mtb versus the immune system: Like the honey badger, Mtb really don''t care.Vaccines primarily work by coaxing our immune system to make antibodies that neutralize foreign invaders, most typically viruses, but also bacteria, some of which have evolved mechanisms to evade detection by antibodies or otherwise render them useless. In most cases, phagocytes then gobble up and kill invading bacteria. While phagocytes are critical in controlling Mtb infections, it is unclear which of their molecules or “effectors” act as executioners of Mtb. For example, nitric oxide and copper play roles in controlling Mtb in a mouse model, but it is unknown how these molecules exert their host‐protective activity, and whether or not they play a similar role in humans. Furthermore, despite the production of these antibacterial effectors—the “porcupine quills”—Mtb often persists due to intrinsic resistance mechanisms. Thus, while our immune system may have the tools to keep Mtb under control, it falls short of eradicating it from our bodies and, in many cases, fails to prevent the progression of the disease. Perhaps a most worrying observation is that prior infection, which is generally considered the most effective path to immunity for many infectious diseases, does not consistently protect against reinfection with Mtb.The above facts have left the TB field scrambling to identify new ways to fight this disease. Much of this work requires that researchers understand both the fundamental processes of the bacterium and its host. Studies of human populations around the globe have revealed differences in susceptibility to infection, the genetic and immunological bases of which are being investigated (Bellamy et al, 2000; Berry et al, 2010; Möller et al, 2010). These studies have made researchers increasingly aware that how the immune system responds to Mtb may play a critical role in disease control. For example, understanding why some individuals or populations are more or less susceptible to TB may help in the development of better vaccines. Also, the more we understand what makes this pathogen so resilient to the immune system could facilitate the development of new antibacterial drugs or host‐directed therapies. These questions can only be answered once we fully understand how the host combats Mtb infections, and how the bacteria counteract these host defenses. While it is a daunting endeavor, my hope is that the efforts of many laboratories around the world will get a better understanding of the host–Mtb interface and ultimately help to eradicate this disease for good.     

miR‐9‐5p suppresses pro‐fibrogenic transformation of fibroblasts and prevents organ fibrosis by targeting NOX4 and TGFBR2

Uncontrolled extracellular matrix (ECM) production by fibroblasts in response to injury contributes to fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). Reactive oxygen species (ROS) generation is involved in the pathogenesis of IPF. Transforming growth factor‐β1 (TGF‐β1) stimulates the production of NADPH oxidase 4 (NOX4)‐dependent ROS, promoting lung fibrosis (LF). Dysregulation of microRNAs (miRNAs) has been shown to contribute to LF. To identify miRNAs involved in redox regulation relevant for IPF, we performed arrays in human lung fibroblasts exposed to ROS. miR‐9‐5p was selected as the best candidate and we demonstrate its inhibitory effect on TGF‐β receptor type II (TGFBR2) and NOX4 expression. Increased expression of miR‐9‐5p abrogates TGF‐β1‐dependent myofibroblast phenotypic transformation. In the mouse model of bleomycin‐induced LF, miR‐9‐5p dramatically reduces fibrogenesis and inhibition of miR‐9‐5p and prevents its anti‐fibrotic effect both in vitro and in vivo. In lung specimens from patients with IPF, high levels of miR‐9‐5p are found. In omentum‐derived mesothelial cells (MCs) from patients subjected to peritoneal dialysis (PD), miR‐9‐5p also inhibits mesothelial to myofibroblast transformation. We propose that TGF‐β1 induces miR‐9‐5p expression as a self‐limiting homeostatic response.     

Coinfection with a virus constrains within‐host infection load but increases transmission potential of a highly virulent fungal plant pathogen

The trade‐off between within‐host infection rate and transmission to new hosts is predicted to constrain pathogen evolution, and to maintain polymorphism in pathogen populations. Pathogen life‐history stages and their correlations that underpin infection development may change under coinfection with other parasites as they compete for the same limited host resources. Cross‐kingdom interactions are common among pathogens in both natural and cultivated systems, yet their impacts on disease ecology and evolution are rarely studied. The host plant Plantago lanceolata is naturally infected by both Phomopsis subordinaria, a seed killing fungus, as well as Plantago lanceolata latent virus (PlLV) in the Åland Islands, SW Finland. We performed an inoculation assay to test whether coinfection with PlLV affects performance of two P. subordinaria strains, and the correlation between within‐host infection rate and transmission potential. The strains differed in the measured life‐history traits and their correlations. Moreover, we found that under virus coinfection, within‐host infection rate of P. subordinaria was smaller but transmission potential was higher compared to strains under single infection. The negative correlation between within‐host infection rate and transmission potential detected under single infection became positive under coinfection with PlLV. To understand whether within‐host and between‐host dynamics are correlated in wild populations, we surveyed 260 natural populations of P. lanceolata for P. subordinaria infection occurrence. When infections were found, we estimated between‐hosts dynamics by determining pathogen population size as the proportion of infected individuals, and within‐host dynamics by counting the proportion of infected flower stalks in 10 infected plants. In wild populations, the proportion of infected flower stalks was positively associated with pathogen population size. Jointly, our results suggest that the trade‐off between within‐host infection load and transmission may be strain specific, and that the pathogen life‐history that underpin epidemics may change depending on the diversity of infection, generating variation in disease dynamics.