Biology subjects

Kahl, S.

Publications and source records attributed to Kahl, S..

5 recordsLinked to original sources

bioRxiv2025

CSF single-cell RNA sequencing reveals clonally expanded CD4+ stem cell-like memory T cells in GAD65-antibody associated neurological syndromes

BackgroundGlutamic acid decarboxylase (GAD) antibody-associated autoimmune neurological syndromes (AINS) are a spectrum of autoimmune-mediated CNS disorders. While antibodies targeting the 65 kDa isoform of GAD are of high diagnostic value, T cell mediated cytotoxicity has been identified as a key component of disease pathogenesis. The precise pathophysiological mechanisms by which the disease is triggered and maintained, however, remain incompletely understood. MethodsWe performed single-cell transcriptome and immune repertoire sequencing (sc-seq) in CSF and blood of 8 anti-GAD65 AINS patients compared to 8 non-inflammatory controls. Monoclonal antibodies (mAbs) were synthesized from B cell receptor (BCR) data to evaluate the B cellular immune response. FindingsWe identified an increase and expansion of activated CD4+ stem cell-like memory T cells (TSCM) in the CSF of anti-GAD65 AINS patients. Expanded T cells showed increased expression of proinflammatory genes. The mAb analysis revealed a high frequency of GAD65-reactive BCRs in the CSF of anti-GAD65 AINS patients with increased somatic hypermutations compared to non-GAD-reactive BCRs and BCRs from controls. ConclusionsSc-seq identified clonally expanded CD4+ TSCM in the CSF of anti-GAD65 AINS patients harboring cytotoxic properties likely contributing to disease pathogenesis. GAD-reactive B cells circulate in the CSF of anti-GAD65 AINS patients further supporting the concept of an antigen-specific intrathecal immune response. Future studies need to clarify the actual pathogenicity of these immune cells and the link between T and B cellular immune mechanisms in the pathogenesis of anti-GAD65 AINS. FundingGerman Research Foundation (ERARE18-202 UltraAIE), German Federal Ministry of Education and Research (CONNECT GENERATE (2.0); 01GM1908A and 01GM2208A).

immunology↗

bioRxiv2025

Liver lipid droplet cholesterol content is a key determinant of metabolic dysfunction-associated steatohepatitis

Metabolic dysfunction-associated steatohepatitis (MASH) represents a progressive form of steatotic liver disease which increases the risk for fibrosis and advanced liver disease. The accumulation of discrete species of bioactive lipids has been postulated to activate signaling pathways that promote inflammation and fibrosis. However, the key pathogenic lipid species is a matter of debate. We explored candidates using various dietary, molecular, and genetic models. Mice fed a choline-deficient L-amino acid-defined high-fat diet (CDAHFD) developed steatohepatitis and manifested early markers of liver fibrosis associated with increased cholesterol content in liver lipid droplets within 5 days without any changes in total liver cholesterol content. Treating mice with antisense oligonucleotides (ASOs) against Coenzyme A synthase (Cosay) or treatment with bempedoic acid or atorvastatin decreased liver lipid droplet cholesterol content and prevented CDAHFD-induced MASH and the fibrotic response. All these salutary effects were abrogated with dietary cholesterol supplementation. Analysis of human liver samples demonstrated that cholesterol in liver lipid droplets was increased in humans with MASH and liver fibrosis and was higher in PNPLA3 I148M (variants rs738409) than in HSD17B13 variants (rs72613567). Together, these data identify cholesterol in liver lipid droplets as a critical mediator of MASH and demonstrate that COASY knockdown and bempedoic acid are novel therapeutic approaches to reduce liver lipid droplet cholesterol content and thereby prevent the development of MASH and liver fibrosis. Significance StatementMetabolic dysfunction-associated steatohepatitis (MASH) is a progressive liver disease linked to fibrosis. The role of specific lipid species in its pathogenesis remains debated. Using dietary, molecular, and genetic models, we found that mice on a choline-deficient, high-fat diet (CDAHFD) developed steatohepatitis and early fibrosis, marked by increased cholesterol in liver lipid droplets within five days. Targeting COASY with antisense oligonucleotides or treating with bempedoic acid or atorvastatin reduced lipid droplet cholesterol and prevented MASH. However, dietary cholesterol supplementation negated these effects. Human liver samples confirmed elevated lipid droplet cholesterol in MASH and fibrosis, especially in PNPLA3 I148M carriers. These findings highlight cholesterol reduction as a potential MASH therapy.

pathology↗

bioRxiv2024

Adaptation and acclimation of gametophytic traits to heat stress in a widely distributed wild plant along a steep climatic gradient

O_LIClimate change-induced heat waves often result in reduced seed yields and quality via high-temperature effects in the gametophytic phase. Surprisingly, the ability of pollen and ovules, particularly among wild plant populations, to adapt or acclimate to heat stress remains poorly understood. C_LIO_LITo address this gap, we examined the adaptive and acclimation potential of six gametophytic traits in eleven distinct populations of wild Silene vulgaris across a temperature gradient in Europe. First, we cultivated plants in a common garden to reveal differences in gametophytic traits indicative of adaptation. Next, we assessed the acclimation potential of these traits to heat stress by subjecting flowering plants to two chronic heat stress (CHS) treatments: moderate (35/30 {degrees}C) and severe (40/35 {degrees}C), for 18 days. C_LIO_LIFindings from the common garden experiment indicated no intraspecific variation in gametophytic traits across the temperature gradient, suggesting that these traits may not influence the plants sexual adaptation to its local habitat. Plants originating from colder climates produced more and larger seeds than those from warmer climates. During CHS treatments, the female gametophyte was less temperature sensitive compared to the male gametophyte. Moderate CHS led to larger ovaries with more, large-sized ovules, while severe CHS reduced ovule numbers but increased their size. In contrast, both CHS treatments decreased pollen grain numbers, size, and anther length, with severe CHS causing more significant reductions. These reductions in gametophytic traits ultimately translated to lower seed yield and quality, which may threaten the sustained existence of natural plant populations over time. Under both CHS treatments, the acclimation potential did not vary among plant populations along the temperature gradient, except for pollen size under severe CHS, with larger pollen size in warmer climates than in colder regions. C_LIO_LIOur findings suggest that the lack of adaptation and acclimation mechanisms in the gametophytic traits (except for pollen size) of wild Silene vulgaris populations along the temperature gradient indicates that these plants may rely on alternative strategies, such as shifts in flowering time, to respond to thermal stress. C_LI

plant biology↗

bioRxiv2024

High-resolution respirometry reveals altered mammalian tissue ketone body oxidation in different cardiometabolic diseases

Background and aimsReduced mitochondrial function has been implicated in metabolic disorders like type 2 diabetes (T2D), obesity, and metabolic dysfunction-associated steatotic liver disease (MASLD), which are tightly linked to insulin resistance and impaired metabolic flexibility. However, the contribution of the ketone bodies (KBs) {beta}-hydroxybutyrate (HBA) and acetoacetate (ACA) as substrates for mitochondrial oxidative phosphorylation (OXPHOS) in these insulin resistant states remains unclear. MethodsTargeted high-resolution respirometry protocols were applied to detect the differential contribution of HBA and ACA to OXPHOS capacity in heart, skeletal muscle, kidney, and liver of distinct human and mouse cohorts with T2D, obesity, and MASLD. ResultsIn humans with T2D, KB-driven mitochondrial OXPHOS capacity was [~]30% lower in the heart (p<0.05) and skeletal muscle (p<0.05) compared to non-diabetic controls. The relative contribution of KB to maximal OXPHOS capacity in T2D was also lower in both the heart ([~]25%, p<0.05) and skeletal muscle ([~]50%, p<0.05). Similarly, in kidney cortex from high-fat diet-induced obese mice, both the absolute and relative contribution of KB to OXPHOS capacity was [~]15% lower (p<0.05). Finally, hepatic HBA-driven mitochondrial OXPHOS capacity was 29% lower (p<0.05) in obese humans with MASLD compared to humans without MASLD. ConclusionsMitochondrial KB-driven OXPHOS capacity is impaired in insulin resistant states in various organs in absolute and relative terms, likely reflecting impaired mitochondrial metabolic flexibility. Our data suggest that KB respirometry can provide a sensitive readout of impaired mitochondrial function in diabetes, obesity, and MASLD.

cell biology↗

bioRxiv2023

Infection and antibiotic-associated changes in the fecal microbiota of C. rodentium {Phi}stx2dact-infected C57BL/6 mice

Enterohemorrhagic E. coli causes watery to bloody diarrhea, which may progress to hemorrhagic colitis and hemolytic-uremic syndrome. While early studies suggested that antibiotic treatment may worsen the pathology of an EHEC infection, recent work has shown that certain non-Shiga toxin-inducing antibiotics avert disease progression. Unfortunately, both intestinal bacterial infections and antibiotic treatment are associated with dysbiosis. This can alleviate colonization resistance, facilitate secondary infections, and potentially lead to more severe illness. To address the consequences in the context of an EHEC infection, we used the established mouse infection model organism C. rodentium {phi}stx2dact and monitored changes in fecal microbiota composition during infection and antibiotic treatment. C. rodentium {phi}stx2dact infection resulted in minor changes compared to antibiotic treatment. The infection caused clear alterations in the microbial community, leading mainly to a reduction of Muribaculaceae and a transient increase in Enterobacteriaceae distinct from Citrobacter. Antibiotic treatments of the infection resulted in marked and distinct variations in microbiota composition, diversity, and dispersion. Enrofloxacin and trimethoprim/sulfamethoxazole, which did not prevent Stx-mediated organ damage, had the least disruptive effects on the intestinal microbiota, while kanamycin and tetracycline, which rapidly cleared the infection, caused a severe reduction in diversity. Kanamycin treatment resulted in the depletion of all but Bacteroidetes genera, whereas tetracycline effects on Clostridia were less severe. Together, these data highlight the need to address the impact of individual antibiotics in the clinical care of life-threatening infections and consider microbiota-regenerating therapies. IMPORTANCEUnderstanding the impact of antibiotic treatment on enterohemorrhagic E. coli (EHEC) infections is crucial for appropriate clinical care. While discouraged by early studies, recent findings suggest certain antibiotics can impede disease progression. Here, we investigated the impact of individual antibiotics on the fecal microbiota in the context of an established EHEC mouse model using C. rodentium {phi}stx2dact. The infection caused significant variations in the microbiota, leading to a transient increase in Enterobacteriaceae distinct from Citrobacter. However, these effects were minor compared to those observed for antibiotic treatments. Indeed, antibiotics that most efficiently cleared the infection also had the most detrimental effect on the fecal microbiota, causing a substantial reduction in microbial diversity. Conversely, antibiotics showing adverse effects or incomplete bacterial clearance had a reduced impact on microbiota composition and diversity. Taken together, our findings emphasize the delicate balance required to weigh the harmful effects of infection and antibiosis in treatment.

microbiology↗