Application of a derivative of human defensin 5 to treat ionizing radiation-induced enterogenic infection.

Enterogenic infection is a common complication for patients with radiation injury and requires efficient therapeutics in the clinic. Herein, we evaluated the promising drug candidate T7E21RHD5, which is a peptide derived from intestinal Paneth cell-secreted human defensin 5. Oral administration of this peptide alleviated the diarrhea symptoms of mice that received total abdominal irradiation (TAI, γ-ray, 12 Gy) and improved survival. Pathologic analysis revealed that T7E21RHD5 elicited an obvious mitigation of ionizing radiation (IR)-induced epithelial damage and ameliorated the reduction in the levels of claudin, zonula occluden 1 and occludin, three tight junction proteins in the ileum. Additionally, T7E21RHD5 regulated the gut microbiota in TAI mice by remodeling ß diversity, manifested as a reversal of the inverted proportion of Bacteroidota to Firmicutes caused by IR. T7E21RHD5 treatment also decreased the abundance of pathogenic Escherichia-Shigella but significantly increased the levels of Alloprevotella and Prevotellaceae_NK3B31, two short-chain fatty acid-producing bacterial genera in the gut. Accordingly, the translocation of enterobacteria and lipopolysaccharide to the blood, as well as the infectious inflammatory responses in the intestine after TAI, was all suppressed by T7E21RHD5 administration. Hence, this versatile antimicrobial peptide possesses promising application prospects in the treatment of IR-induced enterogenic infection.

Mining and rational design of psychrophilic catalases using metagenomics and deep learning models.

A complete catalase-encoding gene, designated soiCat1, was obtained from soil samples via metagenomic sequencing, assembly, and gene prediction. soiCat1 showed 73% identity to a catalase-encoding gene of Mucilaginibacter rubeus strain P1, and the amino acid sequence of soiCAT1 showed 99% similarity to the catalase of a psychrophilic bacterium, Pedobacter cryoconitis. soiCAT1 was identified as a psychrophilic enzyme due to the low optimum temperature predicted by the deep learning model Preoptem, which was subsequently validated through analysis of enzymatic properties. Experimental results showed that soiCAT1 has a very narrow range of optimum temperature, with maximal specific activity occurring at the lowest test temperature (4 °C) and decreasing with increasing reaction temperature from 4 to 50 °C. To rationally design soiCAT1 with an improved temperature range, soiCAT1 was engineered through site-directed mutagenesis based on molecular evolution data analyzed through position-specific amino acid possibility calculation. Compared with the wild type, one mutant, soiCAT1S205K, exhibited an extended range of optimum temperature ranging from 4 to 20 °C. The strategies used in this study may shed light on the mining of genes of interest and rational design of desirable proteins. KEY POINTS: • Numerous putative catalases were mined from soil samples via metagenomics. • A complete sequence encoding a psychrophilic catalase was obtained. • A mutant psychrophilic catalase with an extended range of optimum temperature was engineered through site-directed mutagenesis.

Actin polymerization inhibition by targeting ARPC2 affects intestinal stem cell homeostasis.

Background: The rapid turnover of the intestinal epithelium is driven by the proliferation and differentiation of intestinal stem cells (ISCs). The dynamics of the F-actin cytoskeleton are critical for maintaining intercellular force and the signal transduction network. However, it remains unclear how direct interference with actin polymerization impacts ISC homeostasis. This study aims to reveal the regulatory effects of the F-actin cytoskeleton on the homeostasis of intestinal epithelium, as well as the potential risks of benproperine (BPP) as an anti-tumor drug. Methods: Phalloidin fluorescence staining was utilized to test F-actin polymerization. Flow cytometry and IHC staining were employed to discriminate different types of intestinal epithelial cells. Cell proliferation was assessed through bromo-deoxyuridine (BrdU) and 5-ethynyl-2'-deoxyuridine (EdU) incorporation assays. The proliferation and differentiation of intestinal stem cells were replicated in vitro through organoid culture. Epithelial migration was evaluated through BrdU pulse labeling and chasing in mice. Results: The F-actin content was observed to significantly increase as crypt cells migrated into the villus region. Additionally, actin polymerization in secretory cells, especially in Paneth cells (PCs), was much higher than that in neighboring ISCs. Treatment with the newly identified actin-related protein 2/3 complex subunit 2 (ARPC2) inhibitor BPP led to a dose-dependent increase or inhibition of intestinal organoid growth in vitro and crypt cell proliferation in vivo. Compared with the vehicle group, BPP treatment decreased the expression of Lgr5 ISC feature genes in vivo and in organoid culture. Meanwhile, PC differentiation derived from ISCs and progenitors was decreased by inhibition of F-actin polymerization. Mechanistically, BPP-induced actin polymerization inhibition may activate the Yes1-associated transcriptional regulator pathway, which affects ISC proliferation and differentiation. Accordingly, BPP treatment affected intestinal epithelial cell migration in a dose-dependent manner. Conclusion: Our findings indicate that the regulation of cytoskeleton reorganization can affect ISC homeostasis. In addition, inhibiting ARPC2 with the Food and Drug Administration-approved drug BPP represents a novel approach to influencing the turnover of intestinal epithelial cells.

Oxymatrine boosts hematopoietic regeneration by modulating MAPK/ERK phosphorylation after irradiation-induced hematopoietic injury.

Hematopoietic toxicity due to ionizing radiation (IR) is a leading cause of death in nuclear incidents, occupational hazards, and cancer therapy. Oxymatrine (OM), an extract originating from the root of Sophora flavescens (Kushen), possesses extensive pharmacological properties. In this study, we demonstrate that OM treatment accelerates hematological recovery and increases the survival rate of mice subjected to irradiation. This outcome is accompanied by an increase in functional hematopoietic stem cells (HSCs), resulting in enhanced hematopoietic reconstitution abilities. Mechanistically, we observed significant activation of the MAPK signaling pathway, accelerated cellular proliferation, and decreased cell apoptosis. Notably, we identified marked increases in the cell cycle transcriptional regulator Cyclin D1 (Ccnd1) and the anti-apoptotic protein BCL2 in HSCs after OM treatment. Further investigation revealed that the expression of Ccnd1 transcript and BCL2 levels were reversed upon specific inhibition of ERK1/2 phosphorylation, effectively negating the rescuing effect of OM. Moreover, we determined that targeted inhibition of ERK1/2 activation significantly counteracted the regenerative effect of OM on human HSCs. Taken together, our results suggest a crucial role for OM in hematopoietic reconstitution following IR via MAPK signaling pathway-mediated mechanisms, providing theoretical support for innovative therapeutic applications of OM in addressing IR-induced injuries in humans.

Phosphate Metabolic Inhibition Contributes to Irradiation-Induced Myelosuppression through Dampening Hematopoietic Stem Cell Survival.

Myelosuppression is a common and intractable side effect of cancer therapies including radiotherapy and chemotherapy, while the underlying mechanism remains incompletely understood. Here, using a mouse model of radiotherapy-induced myelosuppression, we show that inorganic phosphate (Pi) metabolism is acutely inhibited in hematopoietic stem cells (HSCs) during irradiation-induced myelosuppression, and closely correlated with the severity and prognosis of myelosuppression. Mechanistically, the acute Pi metabolic inhibition in HSCs results from extrinsic Pi loss in the bone marrow niche and the intrinsic transcriptional suppression of soluble carrier family 20 member 1 (SLC20A1)-mediated Pi uptake by p53. Meanwhile, Pi metabolic inhibition blunts irradiation-induced Akt hyperactivation in HSCs, thereby weakening its ability to counteract p53-mediated Pi metabolic inhibition and the apoptosis of HSCs and consequently contributing to myelosuppression progression. Conversely, the modulation of the Pi metabolism in HSCs via a high Pi diet or renal Klotho deficiency protects against irradiation-induced myelosuppression. These findings reveal that Pi metabolism and HSC survival are causally linked by the Akt/p53-SLC20A1 axis during myelosuppression and provide valuable insights into the pathogenesis and management of myelosuppression.

CDK19 regulates the proliferation of hematopoietic stem cells and acute myeloid leukemia cells by suppressing p53-mediated transcription of p21.

The cell cycle progression of hematopoietic stem cells (HSCs) and acute myeloid leukemia (AML) cells is precisely controlled by multiple regulatory factors. However, the underlying mechanisms are not fully understood. Here, we find that cyclin-dependent kinase 19 (CDK19), not its paralogue CDK8, is relatively enriched in mouse HSCs, and its expression is more significantly increased than CDK8 after proliferative stresses. Furthermore, SenexinB (a CDK8/19 inhibitor) treatment impairs the proliferation and self-renewal ability of HSCs. Moreover, overexpression of CDK19 promotes HSC function better than CDK8 overexpression. Using CDK19 knockout mice, we observe that CDK19-/- HSCs exhibit similar phenotypes to those of cells treated with SenexinB. Interestingly, the p53 signaling pathway is significantly activated in HSCs lacking CDK19 expression. Further investigations show that CDK19 can interact with p53 to inhibit p53-mediated transcription of p21 in HSCs and treatment with a specific p53 inhibitor (PFTß) partially rescues the defects of CDK19-null HSCs. Importantly, SenexinB treatment markedly inhibits the proliferation of AML cells. Collectively, our findings indicate that CDK19 is involved in regulating HSC and AML cell proliferation via the p53-p21 pathway, revealing a new mechanism underlying cell cycle regulation in normal and malignant hematopoietic cells.

Srebf1c preserves hematopoietic stem cell function and survival as a switch of mitochondrial metabolism.

Mitochondria are fundamental but complex determinants for hematopoietic stem cell (HSC) maintenance. However, the factors involved in the regulation of mitochondrial metabolism in HSCs and the underlying mechanisms have not been fully elucidated. Here, we identify sterol regulatory element binding factor-1c (Srebf1c) as a key factor in maintaining HSC biology under both steady-state and stress conditions. Srebf1c knockout (Srebf1c-/-) mice display increased phenotypic HSCs and less HSC quiescence. In addition, Srebf1c deletion compromises the function and survival of HSCs in competitive transplantation or following chemotherapy and irradiation. Mechanistically, SREBF1c restrains the excessive activation of mammalian target of rapamycin (mTOR) signaling and mitochondrial metabolism in HSCs by regulating the expression of tuberous sclerosis complex 1 (Tsc1). Our study demonstrates that Srebf1c plays an important role in regulating HSC fate via the TSC1-mTOR-mitochondria axis.

CD63 acts as a functional marker in maintaining hematopoietic stem cell quiescence through supporting TGFß signaling in mice.

Hematopoietic stem cell (HSC) fate is tightly controlled by various regulators, whereas the underlying mechanism has not been fully uncovered due to the high heterogeneity of these populations. In this study, we identify tetraspanin CD63 as a novel functional marker of HSCs in mice. We show that CD63 is unevenly expressed on the cell surface in HSC populations. Importantly, HSCs with high CD63 expression (CD63hi) are more quiescent and have more robust self-renewal and myeloid differentiation abilities than those with negative/low CD63 expression (CD63-/lo). On the other hand, using CD63 knockout mice, we find that loss of CD63 leads to reduced HSC numbers in the bone marrow. In addition, CD63-deficient HSCs exhibit impaired quiescence and long-term repopulating capacity, accompanied by increased sensitivity to irradiation and 5-fluorouracil treatment. Further investigations demonstrate that CD63 is required to sustain TGFß signaling activity through its interaction with TGFß receptors I and II, thereby playing an important role in regulating the quiescence of HSCs. Collectively, our data not only reveal a previously unrecognized role of CD63 but also provide us with new insights into HSC heterogeneity.

Caffeic acid attenuates irradiation-induced hematopoietic stem cell apoptosis through inhibiting mitochondrial damage.

Hematopoietic stem cells (HSCs) are sensitive to ionizing radiation (IR) damage, and its injury is the primary cause of bone marrow (BM) hematopoietic failure and even death after exposure to a certain dose of IR. However, the underlying mechanisms remain incompletely understood. Here we show that mitochondrial oxidative damage, which is characterized by mitochondrial reactive oxygen species overproduction, mitochondrial membrane potential reduction and mitochondrial permeability transition pore opening, is rapidly induced in both human and mouse HSCs and directly accelerates HSC apoptosis after IR exposure. Mechanistically, 5-lipoxygenase (5-LOX) is induced by IR exposure and contributes to IR-induced mitochondrial oxidative damage through inducing lipid peroxidation. Intriguingly, a natural antioxidant, caffeic acid (CA), can attenuate IR-induced HSC apoptosis through suppressing 5-LOX-mediated mitochondrial oxidative damage, thus protecting against BM hematopoietic failure after IR exposure. These findings uncover a critical role for mitochondria in IR-induced HSC injury and highlight the therapeutic potential of CA in BM hematopoietic failure induced by IR.

Grape seed proanthocyanidin extract ameliorates ionizing radiation-induced hematopoietic stem progenitor cell injury by regulating Foxo1 in mice.

Ionizing radiation (IR)-induced excessive reactive oxygen species (ROS) is an important contributor of the injury of hematopoietic system. Grape seed proanthocyanidin extract (GSPE) is a new type of antioxidant, whereas whether it could ameliorate IR-induced hematopoietic injury remains unclear. Here, we show that GSPE treatment improves the survival of irradiated mice and alleviates IR-induced myelosuppression. Meanwhile, the hematopoietic reconstituting ability of hematopoietic stem cells (HSCs) in mice following irradiation exposure is significantly increased after GSPE treatment. Furthermore, GSPE treatment can reduce IR-induced ROS production and relieve DNA damage and apoptosis in hematopoietic stem progenitor cells (HSPCs). Interestingly, we find that a critical antioxidant-associated gene fokhead box transcription factor O1 (Foxo1) is significantly decreased in HSPCs after irradiation. Consistently, hematopoietic specific deletion of Foxo1 increases the radiosensitivity of mice. Further investigations reveal that GSPE treatment specifically upregulates the expression of Foxo1, as well as its target genes superoxide dismutase 1 (SOD1), superoxide dismutase 2 (SOD2) and catalase (CAT). Importantly, Foxo1 deficiency largely abolishes the radioprotection of GSPE on HSPCs. Collectively, our data demonstrate that GSPE plays an important role in ameliorating IR-induced HSPC injury via the Foxo1-mediated pathway. Therefore, GSPE may be used as a promising radioprotective agent.

Synthesis of Mitochondria-Anchored Nitroimidazoles with a Versatile NIR Fluorophore for Hypoxic Tumor-Targeting Imaging and Chemoradiotherapy.

Nitroimidazoles are one of the most common radiosensitizers investigated to combat hypoxia-induced resistance to cancer radiotherapy. However, due to poor selectivity distinguishing cancer cells from normal cells, effective doses of radiosensitization are much closer to the doses of toxicity induced by nitroimidazoles, limiting their clinical application. In this work, a tumor-targeting near-infrared (NIR) cyanine dye (IR-808) was utilized as a targeting ligand and an NIR fluorophore tracer to chemically conjugate with different structures of hypoxia-affinic nitroimidazoles. One of the NIR fluorophore-conjugated nitroimidazoles (808-NM2) was identified to preferentially accumulate in hypoxic tumor cells, sensitively outline the tumor contour, and effectively inhibit tumor growth synergistically by chemotherapy and radiotherapy. More importantly, nitroimidazoles were successfully taken into cancer cell mitochondria via 808-NM2 conjugate to exert the synergistic effect of chemoradiotherapy. Regarding the important roles of mitochondria on cancer cell survival and metastasis under hypoxia, 808-NM2 may be hopeful to fight against hypoxic tumors.

Neutrophils-derived Spink7 as one safeguard against experimental murine colitis.

The uncontrolled abnormal intestinal immune responses play important role in eliciting inflammatory bowel disease (IBD), yet the molecular events regulating intestinal inflammation during IBD remain poorly understood. Here, we describe an endogenous, homeostatic pattern that controls inflammatory responses in experimental murine colitis. We show that Spink7 (serine peptidase inhibitor, kazal type 7), the ortholog of human SPINK7, is significantly upregulated in dextran sodium sulfate (DSS)-induced murine colitis model. Spink7-deficient mice showed highly susceptible to experimental colitis characterized by enhanced weight loss, shorter colon length, higher disease activity index and increased colonic tissue destruction. Bone marrow reconstitution experiments demonstrated that expression of Spink7 in the immune compartment makes main contribution to its protective role in colitis. What's more, neutrophils are the primary sources of Spink7 in experimental murine colitis. Loss of Spink7 leads to augmented productions of multiple chemokines and cytokines in colitis. In summary, this study identifies neutrophils-derived endogenous Spink7-mediated control of chemokines/cytokines production as a molecular mechanism contributing to inflammation resolution during colitis.

MicroRNA-21 maintains hematopoietic stem cell homeostasis through sustaining the NF-κB signaling pathway in mice.

Long-term hematopoietic output is dependent on hematopoietic stem cell (HSC) homeostasis which is maintained by a complex molecular network. Among these, microRNAs play crucial roles, while the underlying molecular basis has not been fully elucidated. Here, we show that miR-21 is enriched in murine HSCs, and mice with conditional knockout of miR-21 exhibit an obvious perturbation in normal hematopoiesis. Moreover, significant loss of HSC quiescence and long-term reconstituting ability are observed in the absence of miR-21. Further studies reveal that miR-21 deficiency markedly decreases the NF-κB pathway, accompanied by increased expression of PDCD4, a direct target of miR-21, in HSCs. Interestingly, overexpression of PDCD4 in wild-type HSCs generates similar phenotypes as those of miR-21-deficient HSCs. More importantly, knockdown of PDCD4 can significantly rescue the attenuation of NF-κB activity, thereby improving the defects in miR-21-null HSCs. On the other hand, we find that miR-21 is capable of preventing HSCs from ionizing radiation-induced DNA damage via activation of the NF-κB pathway. Collectively, our data demonstrate that miR-21 is involved in maintaining HSC homeostasis and function, at least in part, by regulating the PDCD4-mediated NF-κB pathway and provide a new insight into the radioprotection of HSCs.

SRC-3 Functions as a Coactivator of T-bet by Regulating the Maturation and Antitumor Activity of Natural Killer Cells.

Natural killer (NK)-cell development and maturation is a well-organized process. The steroid receptor coactivator 3 (SRC-3) is a regulator of the hematopoietic and immune systems; however, its role in NK cells is poorly understood. Here, SRC-3 displayed increased nuclear translocation in NK cells during terminal differentiation and upon inflammatory cytokine stimulation. Targeted deletion of SRC-3 altered normal NK-cell distribution and compromised NK-cell maturation. SRC-3 deficiency led to significantly impaired NK-cell functions, especially their antitumor activity. The expression of several critical T-bet target genes, including Zeb2, Prdm1, and S1pr5, but not T-bet itself, was markedly decreased in NK cells in the absence of SRC-3. There was a physiologic interaction between SRC-3 and T-bet proteins, where SRC-3 was recruited by T-bet to regulate the transcription of the aforementioned genes. Collectively, our findings unmask a previously unrecognized role of SRC-3 as a coactivator of T-bet in NK-cell biology and indicate that targeting SRC-3 may be a promising strategy to increase the tumor surveillance function of NK cells.

MicroRNA-34a deficiency leads to impaired wound closure by augmented inflammation in mice.

BACKGROUND: Proper inflammation resolution is critical for cutaneous wound healing and disordered inflammation resolution results in chronic nonhealing wounds. However, the cellular and molecular mechanisms for resolution of inflammation during skin wound healing are not well understood. MicroRNA-34a is regarded as one tumor suppressor with complexed immune regulatory effects, yet its role during skin wound repair is still unclear. METHODS: Circular full thickness excisional wounds were made on the dorsal skin of C57 mice and miR-34a expression pattern was examined by real time RT-PCR and in situ hybridization. The wound healing rates and histologic morphometric analysis were quantified and compared between wounds treated with antagomir-34a and autologous control antagomir-NC wounds, as well as wounds between miR-34a knockout (KO) and wild type (WT) mice. Immunohistochemistry (IHC) for both MPO and F4/80 were performed to examine the infiltrative neutrophils and macrophages in wounds from miR-34a KO and WT mice. Cytokines including IL-1ß, IL-6, TNF-α and IL-10, were detected and analyzed by real time RT-PCR during wound healing. IHC for IL-6 and p-STAT3 were quantified, and WB for p-STAT3 and IL-6R were examined in wounds of miR-34a KO and WT mice. RESULTS: We found miR-34a was significantly downregulated in the inflammatory phase and back to normal levels in the proliferative phase. Both topical knockdown wounds miR-34a levels by antagomir gel and systematic knockout miR-34a using KO mice resulted in impaired wound healing with delayed re-epithelialization and augmented inflammation. IHC results indicated that there were more residual infiltrative inflammatory cells in the proliferative phase. Moreover, over-activated IL-6/STAT3 signal pathway was identified in the wounds of miR-34a KO mice. CONCLUSIONS: Our findings reveal that miR-34a deficiency augments skin wound inflammation response and leads to impaired wound healing, which suggest that targeted inhibition of miR-34a for tissue repair/regeneration should be with serious consideration.

Megakaryocytes promote bone formation through coupling osteogenesis with angiogenesis by secreting TGF-ß1.

Rationale: The hematopoietic system and skeletal system have a close relationship, and megakaryocytes (MKs) may be involved in maintaining bone homeostasis. However, the exact role and underlying mechanism of MKs in bone formation during steady-state and stress conditions are still unclear. Methods: We first evaluated the bone phenotype with MKs deficiency in bone marrow by using c-Mpl-deficient mice and MKs-conditionally deleted mice. Then, osteoblasts (OBs) proliferation and differentiation and CD31hiEmcnhi tube formation were assessed. The expression of growth factors related to bone formation in MKs was detected by RNA-sequencing and enzyme-linked immunosorbent assays (ELISAs). Mice with specific depletion of TGF-ß1 in MKs were used to further verify the effect of MKs on osteogenesis and angiogenesis. Finally, MKs treatment of irradiation-induced bone injury was tested in a mouse model. Results: We found that MKs deficiency significantly impaired bone formation. Further investigations revealed that MKs could promote OBs proliferation and differentiation, as well as CD31hiEmcnhi vessels formation, by secreting high levels of TGF-ß1. Consistent with these findings, mice with specific depletion of TGF-ß1 in MKs displayed significantly decreased bone mass and strength. Importantly, treatment with MKs or thrombopoietin (TPO) substantially attenuated radioactive bone injury in mice by directly or indirectly increasing the level of TGF-ß1 in bone marrow. MKs-derived TGF-ß1 was also involved in suppressing apoptosis and promoting DNA damage repair in OBs after irradiation exposure. Conclusions: Our findings demonstrate that MKs contribute to bone formation through coupling osteogenesis with angiogenesis by secreting TGF-ß1, which may offer a potential therapeutic strategy for the treatment of irradiation-induced osteoporosis.

AIBP and APOA-I synergistically inhibit intestinal tumor growth and metastasis by promoting cholesterol efflux.

BACKGROUND: The roles played by cholesterol in cancer development and progression represent a popular field in the cancer community. High cholesterol levels are positively correlated with the risk of various types of cancer. APOA-I binding protein (AIBP) promotes the reverse cholesterol transport pathway (RCT) in cooperation with Apolipoprotein A-I (APOA-I) or high-density lipoprotein cholesterol. However, the combined effect of AIBP and APOA-I on intestinal tumor cells is still unclear. METHODS: Immunohistochemistry, western blot and qPCR were performed to investigate the expression of AIBP and APOA-I in intestinal tumor tissues and cell lines. The anti-tumor activity of AIBP and APOA-I was evaluated by overexpression or recombinant protein treatment. Cholesterol efflux and localization of lipid raft-related proteins were analyzed by a cholesterol efflux assay and lipid raft fraction assay, respectively. RESULTS: Here, we reported that both AIBP expression and APOA-I expression were associated with the degree of malignancy in intestinal tumors. Co-overexpression of AIBP and APOA-I more potently inhibited colon cancer cell-mediated tumor growth and metastasis compared to overexpression of each protein individually. Additionally, the recombinant fusion proteins of AIBP and APOA-I exhibited a significant therapeutic effect on tumor growth in Apcmin/+ mice as an inherited intestinal tumor model. The synergistic effect of the two proteins inhibited colon cancer cell migration, invasion and tumor-induced angiogenesis by promoting cholesterol efflux, reducing the membrane raft content, and eventually disrupting the proper localization of migration- and invasion-related proteins on the membrane raft. Moreover, cyclosporine A, a cholesterol efflux inhibitor, rescued the inhibitory effect induced by the combination of AIBP and APOA-I. CONCLUSIONS: These results indicate that the combination of APOA-I and AIBP has an obvious anticancer effect on colorectal cancer by promoting cholesterol efflux.

Succinylated casein-coated peptide-mesoporous silica nanoparticles as an antibiotic against intestinal bacterial infection.

Increasing drug resistance necessitates the discovery of novel bactericides. Human defensin (HD) peptides can eliminate resistant bacteria and are promising candidates for next-generation antibiotics. T7E21R-HD5 is a potent bactericide designed by site mutations at enteric HD5. To facilitate the development of T7E21R-HD5 into an intestinal antibiotic, we employed a mesoporous silica nanoparticle (MSN) as the peptide carrier. Despite its ineffectiveness at killing bacteria, the MSN intensified the outer membrane penetration and inner membrane permeabilization abilities of T7E21R-HD5 and thus enhanced its antibacterial action against multidrug resistant (MDR) E. coli, which broadened the role of MSNs in drug delivery. For the reduction in T7E21R-HD5 losses in the stomach, we further modified MSN@T7E21R-HD5 with succinylated casein (SCN), a milk protein that can be specifically degraded by intestinal protease. SCN coating decreased T7E21R-HD5 release from the MSNs, especially in a highly acidic environment. The controlled release of MSN@T7E21R-HD5 from SCN encapsulation was confirmed in the presence of trypsin. MSN@T7E21R-HD5@SCN was nontoxic to host cells, and it was capable of inactivating MDR E. coli in vivo and alleviating intestinal inflammation by suppressing the production of inflammatory factors TNF-α, IL-1ß, and MMP-9. This study provides a peptide-based nanobiotic with efficacy to combat intestinal infection, especially against drug-resistant bacteria. The biocompatible and readily prepared MSN/SCN delivery system may benefit further intestinal antibiotic design and promote the drug transformation of additional enterogenic functional molecules.

MicroRNA 34a promotes ionizing radiation-induced DNA damage repair in murine hematopoietic stem cells.

Hematopoietic stem cells (HSCs) establish the entire hematopoietic system and maintain lifelong hematopoiesis. Previous studies have reported the significance of microRNAs (miRNAs) in the regulation of self-renewal and differentiation of HSCs. In this study, we show that the expression of miRNA 34a (miR-34a) is markedly up-regulated in HSCs from mice subjected to ionizing radiation (IR). Reduced numbers and DNA damage repair, as well as increased apoptosis, are observed in HSCs from miR-34a-deficient mice induced by irradiation, although miR-34a is dispensable for steady-state hematopoiesis. Further investigations show that HSCs deficient in miR-34a exhibit decreased expressions of DNA repair-associated genes involved in homologous recombination and nonhomologous end joining. Competitive transplantation confirms that loss of miR-34a leads to more severe impairment of the long-term hematopoietic function of HSCs after irradiation exposure. Consistently, treating mice with an miR-34a agomir can significantly alleviate irradiation-induced DNA damage in HSCs. Our findings demonstrate that miR-34a contributes to promoting HSCs' survival after irradiation, which provides a promising approach for protecting HSCs from IR.-Zeng, H., Hu, M., Lu, Y., Zhang, Z., Xu, Y., Wang, S., Chen, M., Shen, M., Wang, C., Chen, F., Du, C., Tang, Y., Su,Y., Chen, S., Wang, J. MicroRNA 34a promotes ionizing radiation-induced DNA damage repair in murine hematopoietic stem cells.

dTMP-GH Fusion Protein Therapy Improves Survival after Radiation Injury Combined with Skin-Burn Trauma in Mice.

Exposure to ionizing radiation combined with traumatic tissue injury is an important life-threatening condition found in the civilian populations after nuclear and radiological events. The significance feature of radiation combined injury (RCI) is the severe combined effect, which makes the injury more complicated. At present, there are limited measures available to treat RCI. Here we show that a chimeric protein dTMP-GH, fusing human growth hormone (hGH) with a tandem dimer of thrombopoietin mimetic peptide (dTMP), could be an effective therapy agent for RCI in a mice model. In this study, using a RCI mouse model exposed to 60Co γ-ray photons (6.0 Gy, 0.3 Gy/min) followed by a 20% total-body-surface-area burns (henceforth called: RB-CI) was established. Administration of dTMP-GH (200 ug/kg) for 10 consecutive days beginning at 24 h after injury improved survival rate during a 30-day observation period compared with the control vehicle group. dTMP-GH treatment also showed enhanced bone marrow hematopoiesis recovery determined by peripheral blood analysis and bone marrow histopathology. Meanwhile, dTMP-GH treatment accelerated skin wound closure and mitigated ileum injury in the RCI model. These results suggest that dTMP-GH may prove to be an effective therapeutic drug for RCI.