The microbiota regulates hematopoietic stem and progenitor cell development by mediating inflammatory signals in the niche

Excessive heavy metal enrichment disturbs liver functions through the gut microbe in the great Himalayan leaf-nosed bat (Hipposideros armiger)

Heavy metal residues in natural ecosystems have emerged as a significant global environmental problem requiring urgent resolution. Because these elements are non-biodegradable, organisms can accumulate excessive levels of heavy metal elements into their tissues. Previous studies suggest that prolonged exposure to heavy metal enrichment poses comprehensive toxicity to various organs in vertebrates. However, few studies have focused on elucidating the molecular mechanism underlying the hepatotoxic effects of heavy metal enrichment in Chiroptera. In this study, 10 Hipposideros armiger individuals were dissected from Yingde City (YD, relatively pollution-free) and Chunwan City (CW, excessive heavy metals emission). Environmental samples were also obtained. To investigate the mechanism of heavy metal toxicity in bat livers, we employed a combination of multi-omics, pathology, and molecular biology methods. Our results revealed significant enrichment of Cd and Pb in the bat livers and food sources in the CW group (P<0.05). Furthermore, prolonged accumulation of heavy metals disrupted hepatic transcription profiles associated with the solute carriers family, the ribosome pathway, ATP usage, and heat shock proteins. Excessive heavy metal enrichment also altered the relative abundance of typical gut microbe taxa significantly (P<0.05), inhibiting tight-junction protein expression. We observed a significant decrease in the levels of superoxide dismutase, glutathione peroxidase, and glutathione (P<0.05), along with elevated reactive oxygen species (ROS) density and malondialdehyde content following excessive heavy metal enrichment. Additionally, hepatic fat accumulation and inflammation injuries were present under conditions of excessive heavy metal enrichment, while the contents of metabolism biomarkers significantly decreased (P<0.05). Consequently, prolonged heavy metal enrichment can induce hepatotoxicity by disturbing the microbes-gut-liver axis and hepatic transcription modes, leading to a decrease in overall metabolic activity in bats. Our study offers strategies for biodiversity conservation and highlights the importance of addressing environmental pollution to raise public awareness.

Aeromonas dhakensis: A Zoonotic Bacterium of Increasing Importance in Aquaculture

Aeromonas dhakensis is increasingly recognised to be an important pathogen responsible for disease losses in warm-water aquaculture and, similar to several other Aeromonas species, it can infect humans. Knowledge of A. dhakensis is accumulating, but this species remains relatively under-investigated compared to its close relative, Aeromonas hydrophila. The significance of A. dhakensis may have been overlooked in disease events of aquatic animals due to issues with reliable identification. Critical to appreciating the importance of this pathogen is the application of dependable molecular tools that enable accurate identification and discrimination from A. hydrophila and other motile aeromonads. This review aims to synthesise the key literature on A. dhakensis, particularly with relevance to aquaculture, including knowledge of the bacterium derived from disease case studies in aquatic hosts. Identification methods and strain phylogeny are discussed, with accurate detection important for prompt diagnosis and for distinguishing strains with heightened virulence. Increasing evidence suggests that A. dhakensis may be more virulent than A. hydrophila and correct identification is required to determine the zoonotic risks posed, which includes concerns for antibiotic-resistant strains. This review provides an impetus to improve species identification in the future and screen strain collections of presumptive Aeromonas spp. retrospectively to reveal the true prevalence and impact of A. dhakensis in aquaculture, the environment, and healthcare settings.

Blood and guts: how the intestinal microbiome shapes hematopoiesis and treatment of hematologic disease

ABSTRACT

Over the past 10 years, there has been a marked increase in recognition of the interplay between the intestinal microbiome and the hematopoietic system. Despite their apparent distance in the body, a large literature now supports the relevance of the normal intestinal microbiota to steady-state blood production, affecting both hematopoietic stem and progenitor cells as well as differentiated immune cells. Microbial metabolites enter the circulation where they can trigger cytokine signaling that influences hematopoiesis. Furthermore, the state of the microbiome is now recognized to affect outcomes from hematopoietic stem cell transplant, immunotherapy, and cellular therapies for hematologic malignancies. Here we review the mechanisms by which microbiotas influence hematopoiesis in development and adulthood as well as the avenues by which microbiotas are thought to impact stem cell transplant engraftment, graft-versus-host disease, and efficacy of cell and immunotherapies. We highlight areas of future research that may lead to reduced adverse effects of antibiotic use and improved outcomes for patients with hematologic conditions.

The impact of gut microbial signals on hematopoietic stem cells and the bone marrow microenvironment

Hematopoietic stem cells (HSCs) undergo self-renewal and differentiation in the bone marrow, which is tightly regulated by cues from the microenvironment. The gut microbiota, a dynamic community residing on the mucosal surface of vertebrates, plays a crucial role in maintaining host health. Recent evidence suggests that the gut microbiota influences HSCs differentiation by modulating the bone marrow microenvironment through microbial products. This paper comprehensively analyzes the impact of the gut microbiota on hematopoiesis and its effect on HSCs fate and differentiation by modifying the bone marrow microenvironment, including mechanical properties, inflammatory signals, bone marrow stromal cells, and metabolites. Furthermore, we discuss the involvement of the gut microbiota in the development of hematologic malignancies, such as leukemia, multiple myeloma, and lymphoma.

Hematopoietic stem cells through the ages: A lifetime of adaptation to organismal demands

Hematopoietic stem cells (HSCs), which govern the production of all blood lineages, transition through a series of functional states characterized by expansion during fetal development, functional quiescence in adulthood, and decline upon aging. We describe central features of HSC regulation during ontogeny to contextualize how adaptive responses over the life of the organism ultimately form the basis for HSC functional degradation with age. We particularly focus on the role of cell cycle regulation, inflammatory response pathways, epigenetic changes, and metabolic regulation. We then explore how the knowledge of age-related changes in HSC regulation can inform strategies for the rejuvenation of old HSCs.