Volume 402, Issue 7

Porphyromonas gingivalis is a bacterial species known to be involved in the pathogenesis of chronic periodontitis, that more recently has been as well associated with Alzheimer’s disease. P. gingivalis expresses a glutaminyl cyclase (PgQC) whose human ortholog is known to participate in the beta amyloid peptide metabolism. We have elucidated the crystal structure of PgQC at 1.95 Å resolution in unbound and in inhibitor-complexed forms. The structural characterization of PgQC confirmed that PgQC displays a mammalian fold rather than a bacterial fold. Our biochemical characterization indicates that PgQC uses a mammalian-like catalytic mechanism enabled by the residues Asp 149 , Glu 182 , Asp 183 , Asp 218 , Asp 267 and His 299 . In addition, we could observe that a non-conserved Trp 193 may drive differences in the binding affinity of ligands which might be useful for drug development. With a screening of a small molecule library, we have identified a benzimidazole derivative rendering PgQC inhibition in the low micromolar range that might be amenable for further medicinal chemistry development.

Bacteria are increasingly relying on biofilms to develop resistance to antibiotics thereby resulting in their failure in treating many infections. In spite of continuous research on many synthetic and natural compounds, ideal anti-biofilm molecule is still not found thereby warranting search for new class of molecules. The current study focuses on exploring anti-biofilm potential of selenocystine against respiratory tract infection (RTI)-causing bacteria. Anti-bacterial and anti-biofilm assays demonstrated that selenocystine inhibits the growth of bacteria in their planktonic state, and formation of biofilms while eradicating preformed-biofilm effectively. Selenocystine at a MIC 50 as low as 42 and 28 μg/mL effectively inhibited the growth of Klebsiella pneumonia and Pseudomonas aeruginosa . The antibacterial effect is further reconfirmed by agar cup diffusion assay and growth-kill assay. Selenocystine showed 30–60% inhibition of biofilm formation in K. pneumonia, and 44–70% in P. aeruginosa respectively. It also distorted the preformed-biofilms by degrading the eDNA component of the Extracellular Polymeric Substance matrix. Molecular docking studies of selenocystine with quorum sensing specific proteins clearly showed that through the carboxylic acid moiety it interacts and inhibits the protein function, thereby confirming its anti-biofilm potential. With further validation selenocystine can be explored as a potential candidate for the treatment of RTIs.

Diabetic nephropathy (DN) is the major life-threatening complication of diabetes, and oxidative stress takes part in its initiation and development. This study was performed to evaluate the effects of carotenoids from Sporidiobolus pararoseus (CSP) on the renal function and oxidative stress status of mice with streptozotocin (STZ)-induced DN. The results indicated that CSP significantly attenuated symptoms of STZ-induced DN shown by decreased fasting blood glucose, reduced urine volume, urine albumin, serum creatinine and serum urea nitrogen, and improved kidney histological morphology. Furthermore, biochemical analysis of serum and kidney revealed a marked increase in oxidative stress of DN mice as evidenced by reduced total antioxidant capacity (T-AOC), decreased activity of antioxidant enzyme -superoxide dismutase (SOD) and increased level of malondialdehyde (MDA). However, treatment with CSP improved oxidative stress status in DN mice as compared with the mice in model group. Exploration of the potential mechanism validated that CSP ameliorated the oxidative stress status in DN mice by activating the expressions of Nrf2, NQO-1, HO-1, GST and CAT in kidney. These data revealed that CSP may retard the progression of DN by ameliorating renal function, improving the oxidative stress status and activating the Nrf2/ARE pathway.

Multiple studies have showed that berberine protects against heart diseases, including obesity-associated cardiomyopathy. However, it is not fully disclosed the potential molecular mechanisms of berberine on controlling cardiac remodeling. Kruppel-like factor (KLF) 4, identified as a critical transcriptional factor, participates in multiple cardiac injuries. The present study was to explore whether KLF4 determined the cardioprotective benefits of berberine in dietary-induced obese mice. High fat diet-induced obese mice were treated with berberine with or without lentivirus encoding Klf4 siRNA, and cardiac parameters were analyzed by multiple biological approaches. In dietary-induced obese mouse model, administration of berberine obviously increased cardiac level of KLF4, which closely correlated with improvement of cardiac functional parameters. Co-treatment of lentivirus encoding Klf4 siRNA abolished cardioprotective benefits of berberine, including induction of cardiac hypertrophy, fibrosis, functional disorders, inflammatory response and oxidative stress. Mechanistically, we found berberine improved cardiac mitochondrial biogenesis and activities, whereas silencing Klf4 decreased berberine-upregulated mitochondrial quality, ATP production and oxygen consumption. Our present study demonstrated that berberine protected against dietary-induced cardiac structural disorders and mitochondrial dysfunction dependent on cardiac KLF4 signaling. Cardiac KLF4 was one of potential therapeutic targets for obesity-induced cardiac injuries.

The molecular pathogenesis of colorectal cancer (CRC) has been widely investigated in recent years. Accumulating evidence has indicated that microRNA (miRNA) dysregulation participates in the processes of driving CRC initiation and progression. Aberrant expression of miR-1301 has been found in various tumor types. However, its role in CRC remains to be elucidated. In the present study, we identified miR-1301 was enriched in normal colorectal tissues and significantly down-regulated in CRC. Decreased level of miR-1301 strongly correlated with aggressive pathological characteristics, including advanced stage and metastasis. Bioinformatics and dual luciferase assay demonstrated that STAT3 is a direct target of miR-1301. Gain and loss-of-function assays showed that miR-1301 had no effect on cell proliferation. Overexpression of miR-1301 suppressed cell migration and invasion capacity of pSTAT3-positive LoVo cells, but not pSTAT3-negative SW480 cells, while inhibition of miR-1301 consistently promoted cell migration and invasion in both cell lines. Additionally, miR-1301 inhibition restored the suppressed migration and invasion of STAT3-knockdown LoVo cells. MiR-1301 functioned as a tumor suppressor to modulate the IL6/STAT3 signaling pathway. In summary, this study highlights the significant role of miR-1301/STAT3 axis in CRC metastasis.

Emerging evidence shows that histone modification and its related regulators are involved in the progression and chemoresistance of multiple tumors including acute myeloid leukemia cells (AML). Our present study found that the expression of histone lysine demethylase Jumonji domain containing-3 (JMJD3) was increased in AML cells as compared with that in human primary bone marrow (HPBM) cells. Knockdown of JMJD3 can decrease the proliferation of AML cells and increase the chemosensitivity of daunorubicin (DNR) and cytarabine (Ara-C). By screening the expression of cytokines involved in AML progression, we found that knockdown of JMJD3 can inhibit the expression of interleukin-6 (IL-6). Recombinant IL-6 (rIL-6) can attenuate si-JMJD3-suppressed proliferation of AML cells. Mechanistically, JMJD3 can positively regulate the promoter activity and transcription of IL-6 mRNA, while had no effect on its mRNA stability. Further, JMJD3 can regulate the expression of p65, which can directly bind with promoter of IL-6 to increase its transcription. Over expression of p65 significantly attenuated si-JMJD3-suppressed expression of IL-6. Collectively, we revealed that JMJD3 can regulate the proliferation and chemosensitivity of AML cells via upregulation of IL-6. It suggested that JMJD3 might be a potential therapy target for AML treatment.

The inhibitory glycine receptor (GlyR) is a principal mediator of fast synaptic inhibition in mammalian spinal cord, brainstem, and higher brain centres. Flavonoids are secondary plant metabolites that exhibit many beneficial physiological effects, including modulatory action on neuronal receptors. Using whole-cell current recordings from recombinant human α 1 GlyRs, expressed in HEK293 cells, we compared the flavonols kaempferol and quercetin, the flavanone naringenin, the flavones apigenin and nobiletin, the isoflavone genistein, and two gingerols, 6-gingerol and 8-gingerol for their modulation of receptor currents. All compounds were inhibitors of the GlyR with IC 50 values ranging between 9.3 ± 2.6 µM (kaempferol) and 46.7 ± 6.5 µM (genistein), following a mixed mode of inhibition. Co-application of two inhibitors revealed distinct binding sites for flavonoids and gingerols. Pore-lining mutants T258A and T258S were strongly inhibited by quercetin and naringenin, but not by 6-gingerol, confirming the existence of distinct binding sites for flavonoids and gingerols. Apigenin, kaempferol, nobiletin, naringenin and 6-gingerol showed biphasic action, potentiating glycine-induced currents at low concentration of both, modulator and glycine, and inhibiting at higher concentrations. Identification of distinct modulatory sites for flavonoids and related compounds may present pharmacological target sites and aid the discovery of novel glycinergic drugs.

Glioblastoma (GBM) is the most common and fatal type of primary malignant tumours in the central nervous system. Cytokines such as interleukins (ILs) play an important role in GBM progression. Our present study found that IL-24 is down-regulated in GBM cells. Recombinant IL-24 (rIL-24) can suppress the in vitro migration and invasion of GBM cells while increase its chemo-sensitivity to temozolomide (TMZ) treatment. rIL-24 negatively regulates the expression of Zeb1, one well known transcription factors of epithelial to mesenchymal transition (EMT) of cancer cells. Over expression of Zeb1 can attenuate IL-24-suppressed malignancy of GBM cells. Mechanistically, IL-24 decreases the protein stability of Zeb1 while has no effect on its mRNA stability. It is due to that IL-24 can increase the expression of FBXO45, which can destabilize Zeb1 in cancer cells. Collectively, we reveal that IL-24 can suppress the malignancy of GBM cells via decreasing the expression of Zeb1. It suggests that targeted activation of IL-24 signals might be a potential therapy approach for GBM treatment.

Meningiomas are the most common non-malignant intracranial tumors. Like most tumors, meningiomas prefer anaerobic glycolysis for energy production (Warburg effect). This leads to an increased synthesis of the metabolite methylglyoxal (MGO). This metabolite is known to react with amino groups of proteins. This reaction is called glycation, thereby building advanced glycation endproducts (AGEs). In this study, we investigated the influence of glycation on two meningioma cell lines, representing the WHO grade I (BEN-MEN-1) and the WHO grade III (IOMM-Lee). Increasing MGO concentrations led to the formation of AGEs and decreased growth in both cell lines. When analyzing the influence of glycation on adhesion, chemotaxis and invasion, we could show that the glycation of meningioma cells resulted in increased invasive potential of the benign meningioma cell line, whereas the invasive potential of the malignant cell line was reduced. In addition, glycation increased the E-cadherin- and decreased the N-cadherin-expression in BEN-MEN-1 cells, but did not affect the cadherin-expression in IOMM-Lee cells.

In order for the intestinal mucosa to absorb dietary proteins they have to be digested into single amino acids or very short peptides of a length of not more than four amino acids. In order to study the efficiency of the digestive endopeptidases to digest folded proteins we have analyzed several target proteins under different conditions, native proteins, heat denatured and acid treated. The three pancreatic serine proteases, trypsin, chymotrypsin, and pancreatic elastase, were found to be remarkable inefficient in cleaving native folded proteins whereas pepsin, which acts at a very low pH (pH 1.2) was much more efficient, possibly due to the denaturing conditions and thereby better accessibility to internal cleavage sites at the low pH. Heat treatment improved the cleavage considerably by all three pancreatic enzymes, but acid treatment followed by return to neutral pH did not have any major effect. Cleavage at the low pH when the protein is in a denatured state, is apparently very efficient. This indicates that pepsin is the prime enzyme cleaving the properly folded native proteins and that the pancreatic enzymes primarily are involved in generating single amino acids or very short peptides for efficient uptake by the intestinal mucosa.