Mice with dysfunctional TGF-β signaling develop altered intestinal microbiome and colorectal cancer resistant to 5FU

Emerging data show a rise in colorectal cancer (CRC) incidence in young men and women that is often chemoresistant. One potential risk factor is an alteration in the microbiome. Here, we investigated the role of TGF-β signaling on the intestinal microbiome and the efficacy of chemotherapy for CRC induced by azoxymethane and dextran sodium sulfate in mice. We used two genotypes of TGF-β-signaling-deficient mice (Smad4^+/? and Smad4^+/?Sptbn1^+/?), which developed CRC with similar phenotypes and had similar alterations in the intestinal microbiome. Using these mice, we evaluated the intestinal microbiome and determined the effect of dysfunctional TGF-β signaling on the response to the chemotherapeutic agent 5-Fluoro-uracil (5FU) after induction of CRC. Using shotgun metagenomic sequencing, we determined gut microbiota composition in mice with CRC and found reduced amounts of beneficial species of Bacteroides and Parabacteroides in the mutants compared to the wild-type (WT) mice. Furthermore, the mutant mice with CRC were resistant to 5FU. Whereas the abundances of E. boltae, B.dorei, Lachnoclostridium sp., and Mordavella sp. were significantly reduced in mice with CRC, these species only recovered to basal amounts after 5FU treatment in WT mice, suggesting that the alterations in the intestinal microbiome resulting from compromised TGF-β signaling impaired the response to 5FU. These findings could have implications for inhibiting the TGF-β pathway in the treatment of CRC or other cancers.     

Sulfated glycosaminoglycans and low-density lipoprotein receptor mediate the cellular entry of Clostridium novyi alpha-toxin

Dear Editor, Clostridium novyi(C.novyi)is a spore-forming anaerobic bacterium and opportunistic pathogen causing severe infectious diseases in humans and animal...     

MicroRNA-99a-3p/GRP94 axis affects metastatic progression of human papillary thyroid carcinoma by regulating ITGA2 expression and localization

Papillary thyroid cancer (PTC) usually has favorable prognosis;however,distant metastasis is a leading cause of death associated with PTC.MicroRNA-99a-3p (miR-9...     

Biodesulfurization of dibenzothiophene by growing cells of Gordonia sp. in batch cultures

A new isolate, identified as Gordonia sp. ZD-7 by 16S rDNA sequence analysis, grew in n-hexadecane containing dibenzothiophene (DBT) which was degraded from 2.8 mM to 0.2 mM within 48 h. Biodesulfurization could be repeatedly performed for more than 190 h, with average desulfurization rates of 5 mmol DBT kg cells (dry wt)⁻¹ h⁻¹.     

Tropic 1808基因重组蛋白对大鼠坐骨神经再生的影响

目的观察Tropic1808基因重组蛋白对坐骨神经损伤后再生的影响。方法SD大鼠16只,分为Tropic1808基因重组蛋白组和生理盐水组,切断左侧坐骨神经,硅胶管套接后两神经断端间距10mm,再生室内注入Tropic 1808基因重组蛋白液(500μg/ml)或生理盐水13μl。术后每4周做一次足迹试验,16周时作神经干动作电位、脊髓前角运动神经元数、腓肠肌纤维截面积、硅胶管中段再生神经等检测。结果Tropic1808基因重组蛋白组SFI的恢复、神经干动作电位、脊髓前角运动神经元数、腓肠肌纤维截面积、硅胶管中段再生神经有髓神经纤维数等结果均明显优于生理盐水组,有统计学意义。电镜观察表明Tropic1808组再生轴突较NS组粗,髓鞘较生理盐水组厚。结论Tropic1808基因重组蛋白有促进大鼠坐骨神经再生的作用。     

Permeation of styryl dyes through nanometer-scale pores in membranes

Styryl dyes are widely used to study synaptic vesicle (SV) recycling in neurons; vesicles are loaded with dye during endocytosis, and dye is subsequently released via exocytosis. During putative kiss-and-run exocytosis, efflux of dye from individual SVs has been proposed to occur via two sequential steps: dissociation from the membrane followed by permeation through a small fusion pore. To improve our understanding of the kinetics of efflux of dye from vesicles during kiss-and-run events, we examined the rates of efflux of different dyes through nanometer-scale pores formed in membranes by the toxins melittin and α-hemolysin; these pores approximate the size of fusion pores measured in neuroendocrine cells. We found that the axial diameter of each dye was a crucial determinant for permeation. Moreover, the two dyes with the largest cross-sectional areas were completely unable to pass through pores formed by a mutant α-hemolysin that has a slightly smaller pore than the wild-type toxin. The overall time constant for efflux (seconds) of each dye was orders of magnitude slower than the time constant for dissociation from membranes (milliseconds). Thus, the permeation step is rate-limiting, and this observation was further supported by atomistic molecular dynamics simulations. Together, the data reported here help provide a framework for interpreting dye destaining rates from secretory vesicles.     

Model development and behavioral assessment of focal cerebral ischemia in rats

Stroke in humans is usually focal and occurs in the Middle Cerebral Artery (MCA) distribution. There are several rat models that mimic strokes clinically seen in human. Severity of ischemia can be determined by occlusion time, arteries occluded i.e. MCA alone or combined with one or both Common Carotid Arteries (CCA), and/or location of the occlusion. In this study three focal cerebral infarctions (stroke) were induced for 90 and 120 minutes due to the occlusion of: the MCA alone (MCAo); MCA plus unilateral CCA (MCAo+1CCAo); and MCA plus bilateral CCA (MCAo+2CCAo). Histological parameters included infarct lesion size and hemispheric swelling. Since functional recovery of clinical deficits in stroke often correlates with the efficacy of anti-ischemic therapy, we focused on the behavioral recovery. We combined many sources to obtain comprehensive guidelines for clinical behavior evaluation. Tests included limb flexion, torso twisting, circling, lateral push resistance, beam balancing and walking, hindlimb placing, and inverted angle-board gripping. Occlusion lasting 90 minutes was found to have consistent and repeatable deficits. Results from our study demonstrate 120 minutes of occlusion produced a 60% morality rate and was therefore dropped. Body weight changes between groups showed that increased occlusion time produced more weight loss. Behavior changes indicated that MCAo+2CCAo for 90 minutes demonstrated assessable and consistent clinical deficits for the screening of potential therapeutics.     

Chemo-enzymatic synthesis of the exocyclic olefin isomer of thymidine monophosphate

Exocyclic olefin variants of thymidylate (dTMP) recently have been proposed as reaction intermediates for the thymidyl biosynthesis enzymes found in many pathogenic organisms, yet synthetic reports on these materials are lacking. Here we report two strategies to prepare the exocyclic olefin isomer of dTMP, which is a putative reaction intermediate in pathogenic thymidylate biosynthesis and a novel nucleotide analog. Our most effective strategy involves preserving the existing glyosidic bond of thymidine and manipulating the base to generate the exocyclic methylene moiety. We also report a successful enzymatic deoxyribosylation of a non-aromatic nucleobase isomer of thymine, which provides an additional strategy to access nucleotide analogs with disrupted ring conjugation or with reduced heterocyclic bases. The strategies reported here are straightforward and extendable towards the synthesis of various pyrimidine nucleotide analogs, which could lead to compounds of value in studies of enzyme reaction mechanisms or serve as templates for rational drug design.