Biology subjects

Kim, S. H.

Publications and source records attributed to Kim, S. H..

4 recordsLinked to original sources

bioRxiv2018

Pasakbumin A controls the growth of Mycobacterium tuberculosis by enhancing the autophagy and production of antibacterial mediators in mouse macrophages

Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (Mtb) and remains a major health problem worldwide. Thus, there is an urgent need to identify new and more effective drugs to treat emerging multidrug-resistant TB (MDR-TB) and to reduce the side effects of anti-TB drugs, such as liver toxicity and other detrimental changes. In this study, to develop a novel candidate drug for effective TB treatment with few side effects in the host, we selected pasakbumin A isolated from Eurycoma longifolia (E. longifolia) Jack, which protected host cells against Mtb infection-induced death. Pasakbumin A significantly inhibited intracellular Mtb growth by inducing autophagy via the ERK1/2-mediated signaling pathway in Mtb-infected macrophages. We further investigated whether pasakbumin A could be used as a potential adjuvant for TB treatment. Treatment with pasakbumin A and the anti-TB drug rifampicin (RMP) potently suppressed intracellular Mtb killing by promoting autophagy as well as TNF- production via the ERK1/2- and NF-{kappa}B-mediated signaling pathways in Mtb-infected cells. Our results suggest that pasakbumin A could be developed as a novel anti-TB drug or host-directed therapeutic (HDT) strategy to protect against host cell death and improve host defense mechanisms against Mtb infection in macrophages.

immunology↗

bioRxiv2018

Renoprotective effects Of Dexmedetomidine against ischemia-reperfusion injury in streptozotocin-induced diabetic rats

BackgroundDiabetic patients are susceptible to renal ischemia-reperfusion injury, which leads to perioperative complications. Nucleotide binding and oligomerization domain (NOD)-like receptor 3 inflammasome participates in the development of diabetes, and contributes to renal ischemia-reperfusion injury. Dexmedetomidine, a highly selective 2-adrenoreceptor agonist, shows renoprotective effects against ischemia-reperfusion injury. We aimed to elucidate the effects, underlying mechanisms, and optimal timing of dexmedetomidine treatment in diabetic rats.\n\nMethodsMale Sprague-Dawley rats (60 animals, weighing 250-300 g) were randomly divided into normal-sham, diabetes-sham, diabetes-ischemia-reperfusion-control, diabetes-ischemia-reperfusion-dexmedetomidine-pre-treatment, and diabetes-ischemia-reperfusion-dexmedetomidine-post-treatment groups. Renal ischemia-reperfusion injury was induced in diabetic rats by occlusion of both renal arteries for 45 minutes followed by reperfusion for 24 hours. Dexmedetomidine (10 g/kg) was administered intraperitoneally 1 hour before ischemia (pre-treatment) or upon reperfusion (post-treatment). After reperfusion, renal tissue was biochemically and histopathologically evaluated.\n\nResultsDexmedetomidine treatment attenuated IR-induced increase in NLRP3, caspase-1, IL-1{beta}, phospho-AKT, and phospho-ERK signaling. Moreover, oxidative stress injury, inflammatory reactions, apoptosis, and renal tubular damage were favorably modulated by dexmedetomidine treatment. Furthermore, post-reperfusion treatment with dexmedetomidine was significantly more effective than pre-treatment in modulating inflammasome, AKT and ERK signaling, and oxidative stress.\n\nConclusionsThis study shows that protective effects of dexmedetomidine in renal ischemia-reperfusion injury are preserved in diabetic conditions and may potentially provide a basis for the use of dexmedetomidine in clinical treatment of renal ischemia-reperfusion injury.

pharmacology and toxicology↗

bioRxiv2018

SAMHD1 Impairs HIV-1 Gene Expression and Reactivation of Viral Latency in CD4+ T-cells

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) restricts human immunodeficiency virus type 1 (HIV-1) replication in non-dividing cells by degrading intracellular deoxynucleoside triphosphates (dNTPs). SAMHD1 is highly expressed in resting CD4+ T-cells that are important for the HIV-1 reservoir and viral latency; however, whether SAMHD1 affects HIV-1 latency is unknown. Recombinant SAMHD1 binds HIV-1 DNA or RNA fragments in vitro, but the function of this binding remains unclear. Here we investigate the effect of SAMHD1 on HIV-1 gene expression and reactivation of viral latency. We found that endogenous SAMHD1 impaired HIV-1 LTR activity in monocytic THP-1 cells and HIV-1 reactivation in latently infected primary CD4+ T-cells. Overexpression of wild-type (WT) SAMHD1 suppressed HIV-1 long terminal repeat (LTR)-driven gene expression at the level of transcription. SAMHD1 overexpression also suppressed LTR activity from human T-cell leukemia virus type 1 (HTLV-1), but not from murine leukemia virus (MLV), suggesting specific suppression of retroviral LTR-driven gene expression. WT SAMHD1 bound to proviral DNA and impaired reactivation of HIV-1 gene expression in latently infected J-Lat cells. In contrast, a nonphosphorylated mutant (T592A) and a dNTP triphosphohydrolase (dNTPase) inactive mutant (H206D/R207N, or HD/RN) of SAMHD1 failed to efficiently suppress HIV-1 LTR-driven gene expression and reactivation of latent virus. Purified recombinant WT SAMHD1, but not T592A and HD/RN mutants, bound to fragments of the HIV-1 LTR in vitro. These findings suggest that SAMHD1-mediated suppression of HIV-1 LTR-driven gene expression contributes to regulation of viral latency in CD4+ T-cells.\n\nIMPORTANCEA critical barrier to developing a cure for HIV-1 infection is the long-lived viral reservoir that exists in resting CD4+ T-cells, the main targets of HIV-1. The viral reservoir is maintained through a variety of mechanisms, including regulation of the HIV-1 LTR promoter. The host protein SAMHD1 restricts HIV-1 replication in non-dividing cells, but its role in HIV-1 latency remains unknown. Here we report a new function of SAMHD1 in regulating HIV-1 latency. We found that SAMHD1 suppressed HIV-1 LTR promoter-driven gene expression and reactivation of viral latency in cell lines and primary CD4+ T-cells. Furthermore, SAMHD1 bound to the HIV-1 LTR in vitro and in a latently infected CD4+ T-cell line, suggesting that the binding may negatively modulate reactivation of HIV-1 latency. Our findings indicate a novel role for SAMHD1 in regulating HIV-1 latency, which enhances our understanding of the mechanisms regulating proviral gene expression in CD4+ T-cells.

microbiology↗

bioRxiv2017

DNA sequence encodes the position of DNA supercoils

The three-dimensional structure of DNA is increasingly understood to play a decisive role in gene regulation and other vital cellular processes, which has triggered an explosive growth of research on the spatial architecture of the genome. Many studies focus on the role of various DNA-packaging proteins, crowding, and confinement in organizing chromatin, but structural information might also be directly encoded in bare DNA itself. Here, we use a fluorescence-based single-molecule technique to visualize plectonemes, the extended intertwined DNA loops that form upon twisting DNA. Remarkably, we find that the underlying DNA sequence directly encodes the structure of supercoiled DNA by pinning plectonemes at specific positions. We explore a variety of DNA sequences to determine what features influence pinning, and we develop a physical model that predicts the level of plectoneme pinning in excellent agreement with the data. The intrinsic curvature measured over a range of ~70 base pairs is found to be the key property governing the supercoiled structure of DNA. Our model predicts that plectonemes are likely to localize directly upstream of prokaryotic transcription start sites, and this prediction is experimentally verified in vitro. Our results reveal a hidden code in DNA that helps to spatially organize the genome.

biophysics↗