Biomedical subjects

Hyung Soo Han

Publications and source records attributed to Hyung Soo Han.

11 recordsLinked to original sources

PubMed2025

Pangenome analysis of Lactobacillus mulieris strains reveals distinct subspecies clusters with defined ecological adaptations.

Lactobacillus mulieris is a recently described species, reportedly isolated from human urine, vagina, and gut. Previous genomic studies of L. mulieris highlighted significant genetic diversity among its strains. To gain a deeper understanding of this genomic diversity, we conducted a comprehensive genomic comparison of 70 L. mulieris strains from diverse sources. Phylogenomic and genome relatedness analysis identified three distinct clades, each representing a potential subspecies cluster. Pangenome analysis revealed distinct gene clusters shaping the functional characteristics and unique ecological adaptations of each clade. Clade 1 demonstrated a generalist lifestyle, with strains isolated from diverse sources and enriched in serine/threonine protein kinases, suggesting adaptive versatility. Clade 2, predominantly composed of urinary isolates, displayed enrichment in genes facilitating nutrient acquisition and osmotic regulation, enabling survival in the nutrient-limited and high osmolarity conditions of the urinary tract. Clade 3, exclusively composed of vaginal isolates, exhibited significant enrichment in genes supporting glycogen metabolism, carbohydrate transport, and capsular polysaccharide biosynthesis-features indicative of adaptation to the vaginal environment. Collectively, our findings provide essential genomic insights into the ecological specialization of L. mulieris, shedding light on their genetic variability and adaptive traits within their respective ecological niches.IMPORTANCERecognizing the genomic diversity within Lactobacillus mulieris is essential for understanding its ecological specialization and adaptation strategies across distinct human-associated environments. By identifying three distinct clades with unique functional traits, our study highlights the critical role of niche-specific genetic adaptations in microbial survival. The presence of specialized gene functions within each clade underscores how evolutionary pressures shape bacterial resilience in different environments. Despite their coexistence in overlapping environments, these clades exhibit distinct genomic profiles that may influence their colonization potential and interactions with the host and within the host-associated microbiota. Our findings emphasize the need for a classification framework that accounts for these genetic and functional differences and the necessity for further investigation to understand their distinct roles and impact on human health.

Humans↗

PubMed2007

No association between dinucleotide repeat polymorphism in intron 1 of the epidermal growth factor receptor gene EGFR and risk of lung cancer.

The tyrosine kinase receptor EGFR pathway is one of the oncogenic signaling cascades involved in lung cancer, mediating the epidermal growth factor receptor gene EGFR. First-intron polymorphisms with greater numbers of CA dinucleotide repeats tend to downregulate EGFR expression, which suggests that this polymorphism may modulate susceptibility to lung cancer. The present hospital-based case-control study evaluated the possible association of CA repeat polymorphism in the EGFR gene with risk of lung cancer in a Korean population. A bimodal pattern appeared, with a frequency of 57.1% for 20 CA repeats and 18.6% for 16 CA repeats. There was, however, no significant difference in distribution of allele genotypes between all lung cancer cases and the controls, nor among histological types for the cases.

Adenocarcinoma↗

PubMed2006

MDM2 309T>G polymorphism and risk of lung cancer in a Korean population.

BACKGROUND: The MDM2 protein plays an important role in regulating cell proliferation and apoptosis by interaction with multiple proteins including p53 and Rb. A polymorphism (309T>G) in the MDM2 promoter has been shown to result in higher levels of MDM2 RNA and protein. In order to evaluate the association of the MDM2 309T>G polymorphism and lung cancer risk, we carried out a case-control study in a Korean population. METHODS: The MDM2 genotypes were determined in 582 lung cancer patients and in 582 healthy control subjects who were frequency matched for age and gender. RESULTS: The distribution of the MDM2 309T>G genotypes was not significantly different between overall lung cancer cases and controls. However, when the cases were categorized by tumor histology, the 309GG genotype was associated with a significantly increased risk of adenocarcinoma (adjusted OR=1.91, 95% CI=1.16-3.14, P=0.01) compared to the 309TT genotype. In addition, the risk of adenocarcinoma increased as the number of 309G alleles increased (P(trend)=0.01). CONCLUSION: Our findings suggest that the MDM2 309T>G polymorphism may be used as a marker for genetic susceptibility to adenocarcinoma of the lung.

Adenocarcinoma↗

PubMed2006

Influence of hypothermia on post-ischemic inflammation: role of nuclear factor kappa B (NFkappaB).

Mild hypothermia is one of the most robust neuroprotectant studied in the laboratory to date. The reasons for this protective effect are likely multifactorial, but work from our laboratory and others have shown that this protection is associated with remarkable suppression of the inflammatory response that accompanies brain ischemia. Consistently, laboratories have shown that small decreases in brain temperature to 30-34 degrees C result in reduced inflammatory cell infiltrate, less microglial activation, and reduction of a variety of inflammatory mediators such as nitric oxide, inflammatory cytokines and superoxide. Nuclear factor-kappaB (NFkappaB) is a transcription factor that is activated after cerebral ischemia. NFkappaB activation leads to the expression of many inflammatory genes involved in the pathogenesis of stroke. Our laboratory has shown that hypothermia decreases NFkappaB translocation and binding activity, by affecting NFkappaB regulatory proteins. Mild hypothermia appears to suppress phosphorylation of NFkappaB's inhibitory protein (IkappaB-alpha) by decreasing expression and activity of IkappaB kinase-gamma (IKK). As a consequence, hypothermia suppressed gene expression of two NFkappaB target genes, inducible nitric oxide synthase and TNF-alpha. These data suggest that the protective effect of hypothermia on cerebral injury is, in part, related to NFkappaB inhibition due to decreased activity of IKK.

Animals↗

PubMed2005

The function and integrity of the neurovascular unit rests upon the integration of the vascular and inflammatory cell systems.

The neurovascular unit is composed of a microvascular endothelium, neuron, and glial cell elements that are in physical proximity to the endothelium. The vascular system provides oxygen, glucose, and hormones for brain cells and guides the cells to appropriately respond to the local environment. Conversely, the brain cells, especially glial cells, can regulate the function of blood vessels in response to local requirements. The disruption of the neurovascular coordination was observed in a variety of inflammation-related diseases in brain, such as infectious diseases, stroke, vascular dementia, and multiple sclerosis. Inflammatory responses resulting from infections or injury of the brain activate the endothelium and glial cells to various degrees depending on the type, titer, or strength and duration of exposure to the agents or insults. The activation of endothelial and microglial cells may be modulated by the action of cytokines or other substances secreted from these cells. In an effort to understand the pathogenesis and find rational treatments against inflammatory disorders in brain, studies have been separately carried out using either endothelial cells or microglia. Increasing evidence, however, indicates that a crosstalk between these two cell types is important for the brain inflammation. Here, we review recent advances that provide insights into the coordinated interaction between the vascular and microglial systems, including the role of the specialized endothelium in regulating the immune response that occurs within CNS, the influence of microglial cells on the properties of endothelial cells, and the effects of endothelium on the state of microglial activation.

Animals↗

PubMed2003

Mild hypothermia inhibits inflammation after experimental stroke and brain inflammation.

BACKGROUND AND PURPOSE: We previously showed that mild hypothermia protects against experimental stroke, even when cooling was delayed by 2 hours. Protection may be due in part to inhibiting inflammation. To clarify, we examined leukocyte infiltration, microglial activation, and adhesion molecule expression in models of stroke and pure brain inflammation. METHODS: Rats underwent 2-hour middle cerebral artery occlusion (MCAO; n=36) or intravenous injection with 5 mg/kg lipopolysaccharide (LPS; n=22). Temperature was lowered to 33 degrees C for 2 hours or kept at 37 degrees C. In MCAO, cooling was applied intraischemically or on reperfusion (delayed). In the LPS model, cooling began after injection. One and 3 days later, brains were assessed for neutrophils, monocytes/microglia, major histocompatibility complex class II antigen, and intercellular adhesion molecule-1 (ICAM-1). RESULTS: One day after MCAO, both intraischemic and delayed hypothermia decreased ICAM-1 (51% and 60%, respectively, versus normothermia; P<0.001), monocytes (63% and 57%; P<0.01), and microglia (55% and 53%; P<0.001). Similar decreases were seen at 3 days for ICAM-1 (91% and 93%; P<0.001), monocytes (62% and 54%; P<0.01), and microglia (55% and 53%; P<0.001). In the LPS model, ED-1-positive cells were not observed in the brain, but hypothermia decreased ICAM-1 (26%; P<0.05), OX6 (56%; P<0.01), and microglia (47%; P<0.01) at 1 day. CONCLUSIONS: Mild hypothermia decreases inflammatory responses in both brain inflammation and stroke, implicating a direct anti-inflammatory effect of cooling. This suggests that hypothermia can attenuate factors contributing to delayed ischemic injury.

Animals↗

PubMed2003

Mild hypothermia inhibits nuclear factor-kappaB translocation in experimental stroke.

Nuclear factor-kappaB (NFkappaB) is a transcription factor that is activated after cerebral ischemia. NFkappaB activation leads to the expression of many inflammatory genes involved in the pathogenesis of stroke. The authors previously showed that mild hypothermia is protective even when cooling begins 2 h after stroke onset. In the present study, they examined the influence of hypothermia on NFkappaB activation. Rats underwent 2 h of transient middle cerebral artery occlusion. Brains were cooled to 33 degrees C immediately after or 2 h after occlusion, and maintained for 2 h. After normothermic ischemia (brain temperature at 38 degrees C), NFkappaB cytoplasmic expression, nuclear translocation, and binding activity were observed as early as 2 h in the ischemic hemisphere and persisted at 24 h. Hypothermia decreased NFkappaB translocation and binding activity but did not alter overall expression. Hypothermia also affected the levels of NFkappaB regulatory proteins by suppressing phosphorylation of NFkappaB's inhibitory protein (IkappaB-alpha) and IkappaB kinase (IKK-gamma) and decreasing IKK activity, but did not alter overall IKK levels. Hypothermia suppressed the expression of two NFkappaB target genes: inducible nitric oxide synthase and TNF-alpha. These data suggest that the protective effect of hypothermia on cerebral injury is, in part, related to NFkappaB inhibition due to decreased activity of IKK.

Animals↗

PubMed2003

Attenuation of nitric oxide synthase isoform expression by mild hypothermia after focal cerebral ischemia: variations depending on timing of cooling.

OBJECT: In this study the authors examined the influence of mild hypothermia on early expression of nitric oxide synthase (NOS) isoforms and peroxynitrite generation after experimental stroke. METHODS: In 82 male Sprague-Dawley rats, middle cerebral artery occlusion was performed for 2 hours by using the intraluminal suture model. The rats were maintained at their normal body temperature or exposed to 2 hours of intraischemic or postischemic (2-hour delay) mild hypothermia. Brains were collected 2, 6, and 24 hours after onset of ischemia for immunohistochemical and Western blot analysis of neuronal (n)NOS and inducible (i)NOS expression and peroxynitrite generation. CONCLUSIONS: Western blots showed significantly increased nNOS and iNOS expression in the ischemic cortex at 2, 6, and 24 hours compared with sham-operated animals. The NOS expression was highest at 24 hours. Postischemic hypothermia attenuated nNOS expression at 6 and 24 hours to a greater extent than intraischemic hypothermia. Intraischemic hypothermia reduced iNOS expression at both 2 and 24 hours, whereas postischemic hypothermia decreased iNOS expression at 24 hours. Results of immunohistochemical studies showed that nNOS colocalized with the neuronal marker MAP-2 at all time points, whereas iNOS was initially localized to vessels, and then localized to activated microglia by 24 hours. Intraischemic but not postischemic hypothermia decreased the number of nitrotyrosine-positive cells in the ischemic cortex at 24 hours. Mild hypothermia significantly but differentially attenuates increases in NOS isoforms, with more robust nNOS suppression when cooling is delayed. This may have important implications for understanding the mechanism of hypothermic neuroprotection and for stroke therapy.

Animals↗

PubMed2003

Cellular targets of brain inflammation in stroke.

Ischemia elicits an inflammatory response in the injured brain that is mediated by various factors, leading to the accumulation of inflammatory cells. These cells, in turn, generate both toxic and reparative substances. The inflammatory reaction, which has a rapid onset and continues after the stroke, is thought to acutely contribute to the evolution of tissue injury. Knowledge of these signaling pathways has led to the identification of a variety of therapeutic targets for stroke treatment, particularly during the reperfusion phase. Whether these targets will be useful in the development of therapies for the treatment of stroke in humans is far from clear, but they provide fertile ground for scientific investigation.

Animals↗

PubMed2002

Gene expression profile analysis in human hepatocellular carcinoma by cDNA microarray.

We performed gene expression profiling of normal and hepatocellular carcinoma (HCC) liver tissues using a high-density microarray that contained 3,063 human cDNA. The results of a microarray hybridization experiment from eight different HCC tissues were analyzed and classified by the Cluster program. Among these differentially-expressed genes, the galectin-3, serine/threonine kinase SGK, translation factor eIF-4A, -4B, -3, fibroblast growth factor receptor, and ribosomal protein L35A were up-regulated; the mRNAs of Nip3, decorin, and the insulin-like growth factor binding protein-3 were down-regulated in HCC. The differential expression of these genes was further confirmed by an RT-PCR analysis. In addition, our data suggest that the gene expression profile of HCC varies according to the histological types.

Carcinoma, Hepatocellular↗

PubMed2002

Influence of mild hypothermia on inducible nitric oxide synthase expression and reactive nitrogen production in experimental stroke and inflammation.

Mild hypothermia is neuroprotective, but the reasons are not well known. Inflammation contributes to ischemic damage; therefore, we examined whether the protection by hypothermia may be attributable to alterations in the inflammation. We examined whether hypothermia might alter the inflammatory cell-associated inducible nitric oxide synthase (iNOS) and subsequent nitric oxide (NO) and peroxynitrite generation in experimental stroke and inflammation. Rats underwent 2 hr of middle cerebral artery occlusion (MCAO). Brain inflammation was modeled by intravenous lipopolysaccharide (LPS) (2 mg/kg) injection. Temperature was maintained at 33 degrees C for 2 hr immediately after MCAO and LPS injection, delayed 2 hr after MCAO or maintained at 38 degrees C. Cultured microglia were activated with LPS and then incubated at 33 or 37 degrees C. Both intraischemic and delayed mild hypothermia attenuated infarct size by 40% (p < 0.05). Immunohistochemistry was performed to identify cell type, iNOS, and peroxynitrite. The majority of iNOS- and peroxynitrite-positive cells were activated microglia-macrophages, and mild hypothermia significantly decreased the numbers of immunoreactive cells at 72 hr by >50% (p < 0.05). After ischemia, mild hypothermia decreased NO production by 40%. Similarly, hypothermia attenuated NO and iNOS in LPS-injected rats, as well as in cultured microglia. Aminoguanidine, an iNOS inhibitor, also attenuated infarct size and NO in ischemic and inflammation models. We conclude that mild hypothermia significantly inhibits the inflammatory response by affecting microglial iNOS-NO generation. Therapies directed against microglia or their activation may be useful in treating stroke.

Animals↗