Biology subjects

Saito, T. B.

Publications and source records attributed to Saito, T. B..

5 recordsLinked to original sources

bioRxiv2026

Insights into tick-pathogen interactions - a single cell RNA sequencing approach of transcriptional changes during ehrlichial infection

Tick-borne diseases represent a significant threat to human and animal health worldwide. In the United States, the blacklegged tick, Ixodes scapularis (I. scapularis), serves as a competent vector for several bacterial pathogens, including Ehrlichia muris eauclairensis (EME). The I. scapularis embryonic cell line (ISE6) is a valuable tool for propagating tick-borne pathogens and studying tick-pathogen interactions. In this study, we examined the cellular complexity of ISE6 cells and their response to EME infection. Single-cell RNA sequencing revealed 15 distinct cell clusters present. Although ISE6 cells are heterogeneous, they do not display transcriptional similarity to any known tick tissues. Notably, this lack of similarity did not influence their susceptibility to EME infection. Our results demonstrated that EME infection induces time-dependent transcriptional changes in ISE6 cells: early infection is characterized by upregulation of genes associated with stress adaptation, mitochondrial function, and metabolic pathways, whereas late infection leads to broad downregulation of genes involved in the cell cycle, DNA replication, and cytoskeletal organization. These findings enhance our understanding of ehrlichial interactions with ISE6 cells and reinforce the utility of this cell line as a resource for isolating and propagating arthropod endosymbionts and tick-borne pathogens. IMPORTANCEThis study provides a single-cell resolution framework for interpreting tick cell line biology during infection with a medically relevant ehrlichial pathogen. Using scRNA-seq, we show that the I. scapularis embryonic-derived ISE6 cell line comprises multiple transcriptionally distinct cell states, yet these states do not map cleanly onto canonical tick tissue signatures, even when compared against a curated reference tissue atlas. Despite this heterogeneity, EME broadly infects ISE6 cell population, indicating that susceptibility is not restricted to a specific cell type. We further define a time-dependent arthropod vector response in which early infection is marked by activation of stress and metabolic adaptation response, followed by late-stage inhibition of key signaling, transcriptional, and proliferative pathways as bacterial burden increases. Together, these findings strengthen the biological interpretation of ISE6 as an in vitro model for tick-pathogen interactions and provide a resource for future mechanistic studies of ehrlichial persistence, replication, and vector competence.

molecular biology↗

bioRxiv2025

Behavioral Manipulation of Ixodes scapularis by Ehrlichia muris eauclairensis: Implications for Tick-Borne Disease Transmission

Tick-borne diseases pose significant risks to both animals and humans, with emerging pathogens like Ehrlichia muris eauclairensis (EME) underscoring the need for a deeper understanding of pathogen-vector interactions and tick fitness. This study investigates the impact of EME on Ixodes scapularis nymphs, revealing significant behavioral changes in EME-positive ticks. These ticks exhibited increased movement speed, faster bite site-seeking for attachment, and prolonged feeding durations compared to control ticks. Proteomic analyses of the tick synganglion during resting and feeding phases identified 196 differentially expressed proteins in EME-positive ticks, including multiple proteins associated with nicotinic acetylcholine signaling pathways. Our findings indicated altered neuropeptide expression related to stimulus response and activity, suggesting changes in neurophysiology. This research provides the first evidence of behavioral manipulation by an Ehrlichia species, indicating that the tick nervous system is a site of bacterial influence and a potential target for interventions. These findings offer new insights into pathogen-vector dynamics that could lead to the development of transmission-blocking therapies, significantly impacting tick fitness and disease transmission. IMPORTANCETick-borne diseases (TBDs) are increasingly affecting humans, pets, and livestock, with cases rising in recent years. Ticks can carry multiple harmful germs, and human activities and environmental are contributing to new TBDs. This study shows that the bacteria Ehrlichia muris eauclairensis (EME) can change the behavior of nymphal black-legged ticks, which spread various diseases. Infected ticks moved faster, attached to hosts more quickly, and fed longer than uninfected ticks. These changes were linked to specific proteins in the ticks nervous system, suggesting that EME manipulates tick behavior. This is the first evidence that an Ehrlichia species can influence tick behavior, potentially increasing disease transmission. Understanding these interactions can help develop strategies to prevent TBDs by targeting the bacterias influence on ticks, ultimately reducing disease spread and improving public health.

microbiology↗

bioRxiv2025

Circulating extracellular vesicles from HIV-1 gp120-treated mice act as endogenous algogens, mediating and maintaining HIV-associated chronic pain

HIV-associated chronic pain (HIV-PAIN) remains prevalent in the post combined antiretroviral therapy era, affecting 30-60% of HIV patients worldwide. The underlying mechanism responsible for the development and maintenance of chronic pain remains unclear. gp120 is a causal factor of the HIV-PAIN and functions as an exogenous algogen. The pain experienced by human HIV-PAIN has been modeled in mice (referred to as mHIV-PAIN) using intrathecal (i.t.) injections of gp120. gp120 is a relatively short-term, static, exogenous algogen that is exhaustible in vivo. In authentic infection, HIV virions serve as the primary source of exogenous gp120, which initiates the early phase of clinical HIV-PAIN. Interestingly, while the source of replenishing gp120 decreases after antiretroviral therapy by suppressing viremia, the prevalence of chronic HIV-PAIN remains stable. To induce chronic pain in mice, gp120 needs to be repeatedly applied by the i.t. route. This raises a key question: Is an endogenous inexhaustible algogen responsible for maintaining the chronicity of HIV-PAIN? In the present study, we isolated circulating small extracellular vesicles (sEV) from mice using our mHIV-PAIN model that is i.t. injected with gp120. We refer to such sEV as gp120-sEV herein. We observed that gp120 is absent in gp120-sEV. Following transfusion of gp120-sEV intrathecally, naive recipient mice exhibit an extensive pain phenotype, including cold pain tested with we newly invented dry ice vapor cold test. RNA-sequence analysis suggests that gp120-sEVs induced expression of genes related to nociception and neuroinflammation pathways. These findings provide direct evidence that circulating sEV function as endogenous long-term "dynamic" algogens that enhance initial pain and extend the chronification of HIV-PAIN in mice, suggesting that chronic HIV-PAIN requires an exogenous algogen (gp120) paired with endogenous algogen (gp120-sEV), and that these components work synchronically to initiate and extend pain chronification. This double algogen concept provides a new insight into the pathogenesis of HIV-PAIN chronification. Our new mechanistic understanding will also assist in identifying new therapeutics to alleviate HIV-PAIN by targeting pathological gp120-sEV.

neuroscience↗

bioRxiv2023

Identification of common sequence motifs shared exclusively among selectively packed exosomal pathogenic microRNAs during rickettsial infections

We previously reported that microRNA (miR)23a and miR30b are selectively sorted into rickettsia-infected, endothelial cell-derived exosomes (R-ECExos). Yet, the mechanism remains unknown. The number of cases of spotted fever rickettsioses has been increasing in recent years, and infections with these bacteria cause life-threatening diseases by targeting brain and lung tissues. Therefore, the aim of the present study is to continue to dissect the molecular mechanism underlying R-ECExos-induced barrier dysfunction of normal recipient microvascular endothelial cells (MECs), depending on their exosomal RNA cargos. Rickettsiae are transmitted to human hosts by the bite of an infected tick into the skin. In the present study we demonstrate that treatment with R-ECExos, which were derived from spotted fever group R parkeri infected human dermal MECs, induced disruptions of the paracellular adherens junctional protein VE-cadherin and breached the paracellular barrier function in recipient pulmonary MECs (PMECs) in an exosomal RNA-dependent manner. Similarly, we did not detect different levels of miRs in parent dermal MECs following rickettsial infections. However, we demonstrated that the microvasculopathy-relevant miR23a-27a-24 cluster and miR30b are selectively enriched in R-ECExos. Bioinformatic analysis revealed that common sequence motifs are shared exclusively among the exosomal, selectively-enriched miR23a cluster and miR30b at different levels. Taken together, these data warrant further functional identification and characterization of a single, bipartition, or tripartition among ACA, UCA, and CAG motifs that guide recognition of microvasculopathy-relevant miR23a-27a-24 and miR30b, and subsequently results in their selective enrichments in R-ECExos.

molecular biology↗

bioRxiv2020

EPAC regulates von Willebrand factor secretion from endothelial cells in a PI3K/eNOS-dependent manner during inflammation

Coagulopathy is associated with both inflammation and infection, including infection with the novel SARS-CoV-2 (COVID-19). Endothelial cells (ECs) fine tune hemostasis via cAMP-mediated secretion of von Willebrand factor (vWF), which promote the process of clot formation. The exchange protein directly activated by cAMP (EPAC) is a ubiquitously expressed intracellular cAMP receptor that plays a key role in stabilizing ECs and suppressing inflammation. To assess whether EPAC could regulate vWF release during inflammation, we utilized our EPAC1-null mouse model and revealed an increased secretion of vWF in endotoxemic mice in the absence of the EPAC1 gene. Pharmacological inhibition of EPAC1 in vitro mimicked the EPAC1-/- phenotype. EPAC1 regulated TNF-triggered vWF secretion from human umbilical vein endothelial cells (HUVECs) in a phosphoinositide 3-kinases (PI3K)/endothelial nitric oxide synthase (eNOS)-dependent manner. Furthermore, EPAC1 activation reduced inflammation-triggered vWF release, both in vivo and in vitro. Our data delineate a novel regulatory role of EPAC1 in vWF secretion and shed light on potential development of new strategies to controlling thrombosis during inflammation. Key PointPI3K/eNOS pathway-mediated, inflammation-triggered vWF secretion is the target of the pharmacological manipulation of the cAMP-EPAC system.

cell biology↗