Group B Streptococcus (GBS) is the major cause of human neonatal infections. A single clone, designated CC17-GBS, accounts for more than 80% of meningitis cases, the most severe form of the infection. However, the events allowing blood-borne GBS to penetrate the brain remain largely elusive. In this study, we identified the host transmembrane receptors α5β1 and αvβ3 integrins as the ligands of Srr2, a major CC17-GBS specific adhesin. Two motifs located in the binding region of Srr2 were responsible for the interaction between CC17-GBS and these integrins. We demonstrated, in a blood-brain barrier cellular model, that both integrins contributed to the adhesion and internalization of CC17-GBS. Strikingly, both integrins were overexpressed during the post-natal period in the brain vessels of the blood-brain and blood-cerebrospinal fluid barriers and contributed to the juvenile susceptibility to CC17-meningitis. Finally, blocking these integrins decreased CC17-GBS crossing into the juvenile mice central nervous system in an in vivo model of meningitis.Our study demonstrates that CC17-GBS exploits integrins for crossing the brain vessels leading to meningitis. Importantly, it provides host molecular insights into neonate’s susceptibility to CC17-GBS meningitis, thereby opening new perspectives for therapeutic and prevention strategies of GBS-elicited meningitis.
Romain Deshayes de Cambronne, Agnès Fouet, Amandine Picart, Anne-Sophie Bourrel, Cyril Anjou, Guillaume Bouvier, Cristina Candeias, Abdelouhab Bouaboud, Lionel Costa, Anne-Cécile Boulay, Martine Cohen-Salmon, Isabelle Plu, Caroline Rambaud, Eva Faurobert, Corinne Albiges-Rizo, Asmaa Tazi, Claire Poyart, Julie Guignot
The effectiveness of virus-specific strategies, including administered HIV-specific mAbs, to target cells that persistently harbor latent, rebound competent HIV genomes during combination antiretroviral therapy (cART) has been limited by inefficient induction of viral protein expression. To examine antibody-mediated viral reservoir targeting without a need for viral induction, we used an anti-CD4 mAb to deplete both infected and uninfected CD4+ T cells. Ten rhesus macaques infected with barcoded SIVmac239M received cART for 93 weeks starting 4 days post-infection. During cART, five animals received 5-6 anti-CD4 antibody administrations and CD4+ T cell populations were then allowed one year on cART to recover. Despite profound CD4+ T cell depletion in blood and lymph nodes, time to viral rebound following cART cessation was not significantly delayed in anti-CD4 treated animals compared with controls. Viral reactivation rates, determined based on rebounding SIVmac239M clonotype proportions, also were not significantly different in CD4 depleted animals. Notably, antibody-mediated depletion was limited in rectal tissue and negligible in lymphoid follicles. These results suggest that even if robust viral reactivation can be achieved, antibody-mediated viral reservoir depletion may be limited in key tissue sites.
Adrienne E. Swanstrom, Taina T. Immonen, Kelli Oswald, Cathi Pyle, James A. Thomas, William J. Bosche, Lorna Silipino, Michael Hull, Laura Newman, Vicky Coalter, Adam Wiles, Rodney Wiles, Jacob Kiser, David R. Morcock, Rebecca Shoemaker, Randy Fast, Matthew W. Breed, Joshua Kramer, Duncan Donohue, Tyler Malys, Christine M. Fennessey, Charles M. Trubey, Claire Deleage, Jacob D. Estes, Jeffrey D. Lifson, Brandon F. Keele, Gregory Q. Del Prete
Renal fibrosis, a common pathological manifestation of virtually all types of chronic kidney diseases (CKD), often results in diffuse kidney scarring and predisposes to end-stage renal disease. Currently, there is no effective therapy against renal fibrosis. Recently, our laboratory identified an ER-resident protein, thioredoxin domain containing 5 (TXNDC5), as a critical mediator of cardiac fibrosis. Transcriptome analyses of renal biopsy specimens from CKD patients revealed marked TXNDC5 upregulation in fibrotic kidneys, suggesting a potential role of TXNDC5 in renal fibrosis. Employing multiple fluorescent reporter mouse lines, we showed that TXNDC5 was specifically upregulated in collagen-secreting fibroblasts in fibrotic mouse kidneys. In addition, we showed that TXNDC5 was required for TGFβ1-induced fibrogenic responses in human kidney fibroblasts (HKF), whereas TXNDC5 over-expression was sufficient to promote HKF activation, proliferation and collagen production. Mechanistically, we showed that TXNDC5, transcriptionally controlled by ATF6-dependent ER stress pathway, mediates its pro-fibrogenic effects by enforcing TGFβ signaling activity through post-translational stabilization and upregulation of type I TGFβ receptor in kidney fibroblasts. Using a tamoxifen-inducible, fibroblast-specific Txndc5 knockout mouse line, we demonstrated that deletion of Txndc5 in kidney fibroblasts mitigated the progression of established kidney fibrosis, suggesting the therapeutic potential of TXNDC5 targeting for renal fibrosis and CKD.
Yen-Ting Chen, Pei-Yu Jhao, Chen-Ting Hung, Yueh-Feng Wu, Sung-Jan Lin, Wen-Chih Chiang, Shuei-Liong Lin, Kai-Chien Yang
Chronic kidney disease (CKD) remains a major epidemiological, clinical and biomedical challenge. During CKD, renal tubular epithelial cells (TECs) suffer a persistent inﬂammatory and proﬁbrotic response. Fatty acid oxidation (FAO), the main source of energy for TECs, is reduced in kidney fibrosis and contributes to its pathogenesis. To determine if FAO gain-of-function (FAO-GOF) could protect from fibrosis, we generated a conditional transgenic mouse model with overexpression of the fatty acid shuttling enzyme carnitine palmitoyl-transferase 1 A (CPT1A) in TECs. Cpt1a knock-in mice subjected to three different models of renal fibrosis (unilateral ureteral obstruction, folic acid nephropathy-FAN and adenine induced nephrotoxicity) exhibited decreased expression of fibrotic markers, a blunted pro-inflammatory response and reduced epithelial cell damage and macrophage influx. Protection from fibrosis was also observed when Cpt1a overexpression was induced after FAN. FAO-GOF restituted oxidative metabolism and mitochondrial number and enhanced bioenergetics increasing palmitate oxidation and ATP levels, changes also recapitulated in TECs exposed to profibrotic stimuli. Studies in patients evidenced decreased CPT1 levels and increased accumulation of short and middle chain acyl-carnitines, reflecting impaired FAO in human CKD. We propose that strategies based on FAO-GOF may constitute powerful alternatives to combat fibrosis inherent to CKD.
Verónica Miguel, Jessica Tituaña, J. Ignacio Herrero, Laura Herrero, Dolors Serra, Paula Cuevas-Delgado, Coral Barbas, Diego Rodriguez-Puyol, Laura Marquez-Exposito, Marta Ruiz-Ortega, Carolina Castillo, Xin Sheng, Katalin Susztak, Miguel Ruiz-Canela, Jordi Salas-Salvado, Miguel A. Martinez-Gonzalez, Sagrario Ortega, Ricardo Ramos-Ruiz, Santiago Lamas
Leber’s hereditary optic neuropathy (LHON) is the most frequent mitochondrial disease and was the first to be genetically defined by a point mutation in the mitochondrial DNA (mtDNA). A molecular diagnosis is reached in up to 95%, the vast majority of which are accounted for by three mutations within mitochondrial complex I (CI) subunit encoding genes in the mtDNA (mtLHON). Here, we resolve the enigma of LHON in the absence of pathogenic mtDNA mutations. We describe biallelic mutations in a nuclear encoded gene, DNAJC30, in 33 unsolved patients from 29 families and establish an autosomal recessive mode of inheritance for LHON (arLHON), which to date has been a prime example of a maternally inherited disorder. Remarkably, all hallmarks of mtLHON are recapitulated, including incomplete penetrance, male predominance, and significant idebenone responsivity. Moreover, by tracking protein turnover in patient-derived cell lines and a DNAJC30-knock-out cellular model, we measure reduced turnover of specific CI N-module subunits and a resultant impairment of CI function. This demonstrates DNAJC30 is to be a chaperone protein needed for the efficient exchange of CI subunits exposed to reactive oxygen species and integral to a mitochondrial CI repair mechanism, thereby providing the first example of a disease resulting from impaired exchange of assembled respiratory chain subunits.
Sarah L. Stenton, Natalia L. Sheremet, Claudia B. Catarino, Natalia Andreeva, Zahra Assouline, Piero Barboni, Ortal Barel, Riccardo Berutti, Igor O. Bychkov, Leonardo Caporali, Mariantonietta Capristo, Michele Carbonelli, Maria Lucia Cascavilla, Peter Charbel Issa, Peter Freisinger, Sylvie Gerber, Daniele Ghezzi, Elisabeth Graf, Juliana Heidler, Maja Hempel, Elise Heon, Yulia S. Itkis, Elisheva Javasky, Josseline Kaplan, Robert Kopajtich, Cornelia Kornblum, Reka Kovacs-Nagy, Tatiana Krylova, Wolfram S. Kunz, Chiara La Morgia, Costanza Lamperti, Christina Ludwig, Pedro F. Malacarne, Alessandra Maresca, Johannes A. Mayr, Jana Meisterknecht, Tatiana Nevinitsyna, Flavia Palombo, Ben Pode-Shakked, Maria S. Shmelkova, Tim M. Strom, Francesca Tagliavini, Michal Tzadok, Amelie T. van der Ven, Catherine Vignal-Clermont, Matias Wagner, Ekaterina Zakharova, Nino Zhorzholadze, Jen-Michel Rozet, Valerio Carelli, Polina Tsygankova, Thomas Klopstock, Ilka Wittig, Holger Prokisch
DREAM is a transcriptional repressor complex that regulates cell proliferation and its loss causes neonatal lethality in mice. To investigate DREAM function in adult mice, we utilized an assembly defective p107 protein and conditional deletion of its redundant family member p130. In the absence of DREAM assembly, mice displayed shortened survival characterized by systemic amyloidosis, but no evidence of excessive cellular proliferation. Amyloid deposits were found in the heart, liver, spleen, and kidneys, but not the brain or bone marrow. Using laser capture microdissection followed by mass spectrometry, we identified apolipoproteins as the most abundant components of amyloids. Intriguingly, apoA-IV was the most detected amyloidogenic protein in amyloid deposits, suggesting AApoAIV amyloidosis. AApoAIV is a recently described form whereby wildtype apoA-IV has been shown to predominate in amyloid plaques. We determined that DREAM directly regulates Apoa4 by chromatin immunoprecipitation and that the histone variant H2AZ is reduced from the Apoa4 gene body in DREAM’s absence, leading to overexpression. Collectively, we describe a mechanism by which epigenetic misregulation causes apolipoprotein overexpression and amyloidosis, potentially explaining the origins of non-genetic amyloid subtypes.
Pirunthan Perampalam, Haider M. Hassan, Grace E. Lilly, Daniel T. Passos, Joseph Torchia, Patti K. Kiser, Andrea Bozovic, Vathany Kulasingam, Frederick A. Dick
Mutations affecting mitochondrial coenzyme Q (CoQ) biosynthesis lead to kidney failure due to selective loss of podocytes, essential cells of the kidney filter. Curiously, neighboring tubular epithelial cells are spared early in disease, despite higher mitochondrial content. We sought to illuminate non-canonical, cell-specific roles for CoQ, independent of the electron transport chain (ETC). Here we demonstrate that CoQ depletion caused by Pdss2 enzyme deficiency in podocytes results in perturbations in polyunsaturated fatty acid (PUFA) metabolism and the Braf/Mapk pathway, rather than ETC dysfunction. Single nucleus RNA sequencing from kidneys of Pdss2kd/kd mice with nephrotic syndrome and global CoQ-deficiency identified a podocyte-specific perturbation of the Braf/Mapk pathway. Treatment with GDC-0879, a Braf/Mapk-targeting compound ameliorated kidney disease in Pdss2kd/kd mice. Mechanistic studies in Pdss2-depleted podocytes revealed a previously unknown perturbation in PUFA metabolism that was confirmed in vivo. Gpx4, an enzyme that protects against PUFA-mediated lipid peroxidation, was elevated in disease and restored after GDC-0879 treatment. We demonstrate broader human disease relevance by uncovering patterns of GPX4 and Braf/Mapk pathway gene expression in tissue from patients with kidney diseases. Our studies reveal ETC-independent roles for CoQ in podocytes and point to Braf/Mapk as a candidate pathway for the treatment of kidney diseases.
Eriene-Heidi Sidhom, Choah Kim, Maria Kost-Alimova, May Theng Ting, Keith Keller, Julian Avila-Pacheco, Andrew J.B. Watts, Katherine A. Vernon, Jamie L. Marshall, Estefanía Reyes-Bricio, Matthew Racette, Nicolas Wieder, Giulio Kleiner, Elizabeth J. Grinkevich, Fei Chen, Astrid Weins, Clary B. Clish, Jillian L. Shaw, Catarina M. Quinzii, Anna Greka
Innate lymphoid cells (ILCs) are enriched at barrier surfaces, including the gastrointestinal tract. While most studies have focused on the balance between pathogenic group 1 ILCs (ILC1s) and protective ILC3s in maintaining gut homeostasis and during chronic intestinal inflammation, such as Crohn’s disease (CD), less is known regarding ILC2s. Using an established murine model of CD-like ileitis, i.e., SAMP1/YitFc (SAMP) strain, we showed that ILC2s, compared to ILC1s and ILC3s, were increased within draining mesenteric lymph nodes and ilea of SAMP vs. AKR (parental control) mice early, during the onset of disease. Gut-derived ILC2s from Crohn’s patients vs. healthy controls were also increased and expand, similar to ILC1s, in greater proportion compared to ILC3s. Importantly, we report that the intracellular bacterial-sensing protein, nucleotide-binding oligomerization domaining-containing protein-2, encoded by NOD2, the first and strongest susceptibility gene identified for CD, promoted ILC2 expansion, which was dramatically reduced in SAMP lacking NOD2 and SAMP raised under germ-free conditions. Furthermore, these effects occurred through a mechanism involving the IL-33/ST2 ligand-receptor pair. Collectively, our results indicate a functional link between NOD2 and ILC2s, regulated by the IL-33/ST2 axis, that mechanistically may contribute to early events leading to CD pathogenesis.
Carlo De Salvo, Kristine-Ann Buela, Brecht Creyns, Daniele Corridoni, Nitish Rana, Hannah L. Wargo, Chiara Cominelli, Peter G. Delaney, Fabio Cominelli, Alexander Rodriguez-Palacios, Séverine Vermeire, Theresa T. Pizarro
Limited evidence exists regarding the use of the currently approved COVID-19 mRNA vaccines (Pfizer-BioNtech BNT162b2 and Moderna mRNA-1273) during pregnancy. In this Viewpoint, Klein et al. discuss gaps in knowledge and make recommendations to incorporate age, sex, and pregnancy in the preclinical and clincal vaccine development pipeline.
Sabra L. Klein, Patrick S. Creisher, Irina Burd
In order to sustain proficient life-long hematopoiesis, hematopoietic stem cells (HSCs) must possess robust mechanisms to preserve their quiescence and genome integrity. DNA-damaging stress can perturb HSC homeostasis by affecting their survival, self-renewal and differentiation. Ablation of the kinase ATM, a master regulator of the DNA damage response, impairs HSC fitness. Paradoxically, we show here that loss of a single allele of Atm enhances HSC functionality in mice. To explain this observation, we explored a possible link between ATM and the tumor suppressor PTEN, which also regulates HSC function. We generated and analyzed a knock-in mouse line (PtenS398A/S398A), in which PTEN cannot be phosphorylated by ATM. Similar to Atm+/-, PtenS398A/S398A HSCs have enhanced hematopoietic reconstitution ability, accompanied by resistance to apoptosis induced by genotoxic stress. Single-cell transcriptomic analyses and functional assays revealed that dormant PtenS398A/S398A HSCs aberrantly tolerate elevated mitochondrial activity and the accumulation of reactive oxygen species, which are normally associated with HSC priming for self-renewal or differentiation. Our results unveil a molecular connection between ATM and PTEN, which couples the response to genotoxic stress and dormancy in HSC.
Jerome Fortin, Christian Bassi, Parameswaran Ramachandran, Wanda Y. Li, Ruxiao Tian, Ida Zarrabi, Graham Hill, Bryan E. Snow, Jillian Haight, Chantal Tobin, Kelsey Hodgson, Andrew Wakeham, Vuk Stambolic, Tak W. Mak
Lymphatic filariasis is the major global cause of non-hereditary lymphoedema. We demonstrate the filarial nematode, Brugia malayi, induces lymphatic remodelling and impaired lymphatic drainage following parasitism of limb lymphatics in a mouse model. Lymphatic insufficiency was associated with elevated circulating lymphangiogenic mediators, including vascular endothelial growth factor C. Lymphatic insufficiency was dependent on type-2 adaptive immunity, interleukin-4 receptor, recruitment of C-C chemokine receptor-2 monocytes and alternatively-activated macrophages with pro-lymphangiogenic phenotype. Oral treatments with second-generation tetracyclines improved lymphatic function, while other classes of antibiotic had no significant effect. Second-generation tetracyclines directly targeted lymphatic endothelial cell proliferation and modified type-2 pro-lymphangiogenic macrophage development. Doxycycline treatment impeded monocyte recruitment, inhibited polarisation of alternatively-activated macrophages and suppressed T cell adaptive immune responses following infection. Our results determine a mechanism-of-action for the anti-morbidity effects of doxycycline in filariasis and supports clinical evaluation of second-generation tetracyclines as affordable, safe therapeutics for lymphoedemas of chronic inflammatory origin.
Julio Furlong-Silva, Stephen D. Cross, Amy E. Marriott, Nicolas Pionnier, John Archer, Andrew Steven, Stefan Schulte-Merker, Matthias Mack, Young-Kwon Hong, Mark J. Taylor, Joseph D. Turner
Characterization of the T cell response in individuals who recover from SARS-CoV-2 infection is critical to understand its contribution to protective immunity. A multiplexed peptide-MHC tetramer approach was used to screen 408 SARS-CoV-2 candidate epitopes for CD8+ T cell recognition in a cross-sectional sample of 30 COVID-19 convalescent individuals. T cells were evaluated using a 28-marker phenotypic panel, and findings were modelled against time from diagnosis, humoral and inflammatory responses. There were 132 SARS-CoV-2-specific CD8+ T cell responses detected across six different HLAs, corresponding to 52 unique epitope reactivities. CD8+ T cell responses were detected in almost all convalescent individuals and were directed against several structural and non-structural target epitopes from the entire SARS-CoV-2 proteome. A unique phenotype for SARS-CoV-2-specific T cells was observed that was distinct from other common virus-specific T cells detected in the same cross-sectional sample and characterized by early differentiation kinetics. Modelling demonstrated a coordinated and dynamic immune response characterized by a decrease in inflammation, increase in neutralizing antibody titer, and differentiation of a specific CD8+ T cell response. Overall, T cells exhibited distinct differentiation into stem-cell and transitional memory states, subsets, which may be key to developing durable protection.
Hassen Kared, Andrew D. Redd, Evan M. Bloch, Tania S. Bonny, Hermi R. Sumatoh, Faris Kairi, Daniel Carbajo, Brian Abel, Evan W. Newell, Maria Bettinotti, Sarah E. Benner, Eshan U. Patel, Kirsten Littlefield, Oliver Laeyendecker, Shmuel Shoham, David Sullivan, Arturo Casadevall, Andrew Pekosz, Alessandra Nardin, Michael Fehlings, Aaron AR Tobian, Thomas C. Quinn
Gene editing holds the potential to correct mutations and cure devastating genetic disorders. The technology has not yet proven efficacious for therapeutic use in central nervous system (CNS) diseases with ubiquitous neuronal defects. Angelman syndrome (AS), a severe neurodevelopmental disorder, is caused by a lack of maternal expression of the UBE3A gene. Due to genomic imprinting, only neurons are affected. One therapeutic approach focuses on the intact paternal UBE3A copy in AS patients that is silenced by an antisense transcript (UBE3A-ATS). We show here that gene editing of Ube3a-ATS in the mouse brain results in the formation of base pair insertions/deletions (indels) in neurons and the subsequent unsilencing of the paternal Ube3a allele in neurons, which partially corrects the behavior phenotype of a murine AS model. This study provides compelling evidence to further investigate editing of the homologous region of the human UBE3A-ATS, since this may provide a lasting therapeutic effect for AS patients.
Ralf S. Schmid, Xuefeng Deng, Priyalakshmi Panikker, Msema Msackyi, Camilo Breton, James M. Wilson
The emergence of drug-resistant fungi has prompted an urgent threat alert from the Centers for Disease Control. Biofilm assembly by these pathogens further impairs effective therapy. We recently identifed an antifungal, turbinmicin, that inhibits the fungal vesicle-mediated trafficking pathway and demonstrates broad-spectrum activity against planktonically growing fungi. During biofilm growth, vesicles with unique features play a critical role in the delivery of the biofilm extracellular matrix components. As these components are largely responsible for the drug resistance associated with biofilm growth, we explored the utility of turbinmicin in the biofilm setting. We found that turbinmicin disrupts extracellular vesicle delivery during biofilm growth, and this impairs the subsequent assembly of the biofilm matrix. We demonstrated that elimination of the extracellular matrix renders the drug-resistant biofilm communities susceptible to fungal killing by turbinmicin. Furthermore, the addition of turbinmicin to otherwise ineffective antifungal therapy potentiated the activity of these drugs. The underlying role of vesicles explains this dramatic activity and was supported by phenotype reversal with the addition of exogenous biofilm extracellular vesicles. This striking capacity to cripple biofilm assembly mechanisms reveals a new approach to eradicating biofilms and sheds light on turbinmicin as a promising anti-biofilm drug.
Miao Zhao, Fan Zhang, Robert Zarnowski, Kenneth J. Barns, Ryley Jones, Jen L. Fossen, Hiram Sanchez, Scott R. Rajski, Anjon Audhya, Tim S. Bugni, David R. Andes
Lysosomal dysfunction caused by mutations in lysosomal genes results in lysosomal storage disorder (LSD), characterized by accumulation of damaged proteins and organelles in cells and functional abnormalities in major organs, including the heart, skeletal muscle and liver. In LSD, autophagy is inhibited at the lysosomal degradation step and accumulation of autophagosomes is observed. Enlargement of the left ventricle (LV) and contractile dysfunction were observed in RagA/B cardiac-specific knockout (cKO) mice, a mouse model of LSD in which lysosomal acidification is impaired irreversibly. YAP, a downstream effector of the Hippo pathway, was accumulated in RagA/B cKO mouse hearts. Inhibition of YAP ameliorated cardiac hypertrophy and contractile dysfunction and attenuated accumulation of autophagosomes without affecting lysosomal function, suggesting that YAP plays an important role in mediating cardiomyopathy in RagA/B cKO mice. Cardiomyopathy was also alleviated by downregulation of Atg7, an intervention to inhibit autophagy, whereas it was exacerbated by stimulation of autophagy. YAP physically interacted with transcription factor EB (TFEB), a master transcription factor that controls autophagic and lysosomal gene expression, thereby facilitating accumulation of autophagosomes without degradation. These results indicate that accumulation of YAP in the presence of LSD promotes cardiomyopathy by stimulating accumulation of autophagosomes through activation of TFEB.
Shohei Ikeda, Jihoon Nah, Akihiro Shirakabe, Peiyong Zhai, Shin-ichi Oka, Sebastiano Sciarretta, Kun-Liang Guan, Hiroaki Shimokawa, Junichi Sadoshima
Human metabolic incorporation of non-human sialic acid (Sia) N-glycolylneuraminic acid into endogenous glycans generates inflammation via pre-existing antibodies, likely contributing to red-meat-induced atherosclerosis acceleration. Exploring if this mechanism affects atherosclerosis in end-stage renal disease (ESRD), we instead found serum accumulation of 2-keto-3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (Kdn), a Sia prominently expressed in cold-blooded vertebrates. Levels of Kdn precursor mannose also increased but within normal range in ESRD patients. Mannose ingestion by healthy volunteers raised urinary mannose and Kdn. Kdn production pathways remain conserved in mammals but were diminished by a M42T substitution in a key biosynthetic enzyme, N-acetylneuraminate synthase. Remarkably, reversion to the ancestral methionine then occurred independently in two lineages, including humans. However, mammalian glycan databases contain no Kdn-glycans. We hypothesize that potential toxicities of excess mannose in mammals is partly buffered by conversion to free Kdn. Thus, mammals likely conserved Kdn biosynthesis and modulated it in lineage-specific manner, not for glycosylation, but to control physiological mannose intermediates/metabolites. However, human cells can be forced to express Kdn-glycans, via genetic mutations enhancing Kdn utilization, or by transfection with fish enzymes producing CMP-Kdn. Antibodies against Kdn-glycans occur in pooled human immunoglobulins. Pathological conditions that elevate Kdn levels could therefore result in antibody-mediated inflammatory pathologies.
Kunio Kawanishi, Sudeshna Saha, Sandra Diaz, Michael Vaill, Aniruddha Sasmal, Shoib S. Siddiqui, Biswa P. Choudhury, Kumar Sharma, Xi Chen, Ian C. Schoenhofen, Chihiro Sato, Ken Kitajima, Hudson H. Freeze, Anja Münster-Kühnel, Ajit Varki
Previous studies have shown that nitric oxide (NO) supplements may prevent bone loss and fractures in preclinical models of estrogen deficiency. However, the mechanisms by which NO modulates bone anabolism remain largely unclear. Argininosuccinate lyase (ASL) is the only mammalian enzyme capable of synthesizing arginine, the sole precursor for nitric oxide synthase (NOS)-dependent NO synthesis. Moreover, ASL is also required for channeling extracellular arginine to NOS for NO production. ASL deficiency (ASLD) is thus a model to study cell-autonomous, NOS-dependent NO deficiency. Here, we report that loss of ASL led to decreased NO production and impairment of osteoblast differentiation. Mechanistically, the bone phenotype was at least in part driven by the loss of NO-mediated activation of the glycolysis pathway in osteoblasts that led to decreased osteoblast differentiation and function. Heterozygous deletion of Caveolin-1, a negative regulator of NO synthesis, restored NO production, osteoblast differentiation, glycolysis, and bone mass in a hypomorphic mouse model of ASLD. The translational significance of these preclinical studies was further reiterated by studies conducted in induced pluripotent stem cells (iPSCs) from an individual with ASLD. Taken together, our findings suggest that ASLD is a unique genetic model for studying NO-dependent osteoblast function and that the NO-glycolysis pathway may be a new target to modulate bone anabolism.
Zixue Jin, Jordan Kho, Brian Dawson, Ming-Ming Jiang, Yuqing Chen-Evenson, Saima Ali, Lindsay C. Burrage, Monica Grover, Donna J. Palmer, Dustin L. Turner, Philip Ng, Sandesh C.S. Nagamani, Brendan Lee
Autosomal dominant "sterile alpha motif domain containing 9 (Samd9) and Samd9L (Samd9/9L) syndromes" are a large subgroup of currently established inherited bone marrow failure syndromes that include MIRAGE, ataxia pancytopenia, and familial monosomy 7 syndromes. Samd9/9L genes are located in tandem on chromosome 7 and have been known to be the genes responsible for myeloid malignancies associated with monosomy 7. Additionally, as interferon-inducible genes, Samd9/9L are crucial for protection against viruses. Samd9/9L syndromes are caused by gain-of-function mutations and develop into infantile myelodysplastic syndromes associated with monosomy 7 (MDS/-7) at extraordinarily high frequencies. We generated mice expressing Samd9LD764N, which mimic the MIRAGE syndrome presenting with growth retardation, a short life, bone marrow failure, and multi-organ degeneration. In hematopoietic cells, Samd9LD764N downregulates the endocytosis of transferrin and c-Kit resulting in a rare cause of anemia and a low bone marrow reconstitutive potential that ultimately causes MDS/-7. By contrast, in non-hematopoietic cells we tested, Samd9LD764N upregulated the endocytosis of EGFR by Ship2 phosphatase translocation to the cytomembrane and activated lysosomes, resulting in the reduced expression of surface receptors and signaling. Thus Samd9/9L is a downstream regulator of interferon that controls receptor metabolism, with constitutive activation leading to multi-organ dysfunction.
Akiko Nagamachi, Akinori Kanai, Megumi Nakamura, Hiroshi Okuda, Akihiko Yokoyama, Satoru Shinriki, Hirotaka Matsui, Toshiya Inaba
Chronic pancreatitis affects over 250,000 people in the US and millions worldwide. It is associated with chronic debilitating pain, pancreatic exocrine failure, high-risk of pancreatic cancer, and usually progresses to diabetes. Treatment options are limited and ineffective. We developed a new potential therapy, wherein a pancreatic ductal infusion of 1-2% acetic acid in mice and non-human primates resulted in a non-regenerative, near-complete ablation of the exocrine pancreas, with complete preservation of the islets. Pancreatic ductal infusion of acetic acid in a mouse model of chronic pancreatitis led to resolution of chronic inflammation and pancreatitis-associated pain. Furthermore, acetic acid-treated animals showed improved glucose tolerance and insulin secretion. The loss of exocrine tissue in this procedure would not typically require further management in patients with chronic pancreatitis because they usually have pancreatic exocrine failure requiring dietary enzyme supplements. Thus, this procedure, which should be readily translatable to humans through an endoscopic retrograde cholangiopancreatography (ERCP), may offer a potential innovative non-surgical therapy for chronic pancreatitis that relieves pain and prevents the progression of pancreatic diabetes.
Mohamed Saleh, Kartikeya Sharma, Ranjeet S. Kalsi, Joseph C. Fusco, Anuradha Sehrawat, Jami L. Saloman, Ping Guo, Ting Zhang, Nada Mohamed, Yan Wang, Krishna Prasadan, George Gittes
Primary membranous nephropathy (pMN) is a leading cause of the nephrotic syndrome in adults. In most cases, this autoimmune kidney disease is associated with autoantibodies against the M-type phospholipase A2 receptor (PLA2R1) expressed on kidney podocytes, but the mechanisms leading to glomerular damage remain elusive. Here, we developed a cell culture model using human podocytes and found that anti-PLA2R1 positive pMN patient sera or isolated IgG4, but not IgG4-depleted sera, induce proteolysis of the two essential podocyte proteins synaptopodin and NEPH1 in the presence of complement, resulting in perturbations of the podocyte cytoskeleton. Specific blockade of the lectin pathway prevented degradation of synaptopodin and NEPH1. Anti-PLA2R1-IgG4 directly bound mannose-binding lectin in a glycosylation-dependent manner. In a cohort of pMN patients, we identified increased levels of galactose-deficient IgG4, which correlated with anti-PLA2R1-titers and podocyte damage induced by patient sera. Assembly of the terminal C5b-9 complement complex and activation of the complement receptors C3aR1 or C5aR1 was required to induce proteolysis of synaptopodin and NEPH1 by two distinct proteolytic pathways, mediated by cysteine and aspartic proteinases, respectively. Together, these results demonstrate a mechanism by which aberrantly glycosylated IgG4 activates the lectin pathway and induces podocyte injury in primary membranous nephropathy.
George Haddad, Johan M. Lorenzen, Hong Ma, Noortje de Haan, Harald Seeger, Christelle Zaghrini, Simone Brandt, Malte Kölling, Urs Wegmann, Bence Kiss, Gábor Pál, Péter Gál, Rudolf P. Wuthrich, Manfred Wuhrer, Laurence H. Beck, David J. Salant, Gérard Lambeau, Andreas D. Kistler