Innovative Fusion: Natural Compound-Rhein and PROTACs Unleash Potent VEGFR-2 Degraders.

VEGFR-2 is a prominent therapeutic target in antitumor drug research to block tumor angiogenesis. This study focused on the synthesis and optimization of PROTACs based on the natural product rhein, resulting in the successful synthesis of 15 distinct molecules. In A549 cells, D9 exhibited remarkable antitumor efficacy with an IC50 of 5.88 ± 0.50 µM, which was 15-fold higher compared to rhein (IC50=88.45 ± 2.77 µM). An in-depth study of the effect of D9 on the degradation of VEGFR-2 revealed that D9 was able to induce the degradation of VEGFR-2 in A549 cells in a time-dependent manner. The observed effect was reversible, contingent upon the proteasome and ubiquitination system, and demonstrably linked to CRBN. Further experiments revealed that D9 induced apoptosis in A549 cells and led to cell cycle arrest in the G1 phase. Molecular docking simulations validated the binding mode of D9 to VEGFR, establishing the potential of D9 to bind to VEGFR-2 in its natural state. In summary, this study confirms the feasibility of natural product-bound PROTAC technology for the development of a new generation of VEGFR-2 degraders, offering a novel trajectory for the future development of pharmacological agents targeting VEGFR-2.

In silico and in vitro analyses of a novel FoxO1 agonist reducing Aß levels via downregulation of BACE1.

AIMS: FoxO1 is an important target in the treatment of Alzheimer's disease (AD). However, FoxO1-specific agonists and their effects on AD have not yet been reported. This study aimed to identify small molecules that upregulate the activity of FoxO1 to attenuate the symptoms of AD. METHODS: FoxO1 agonists were identified by in silico screening and molecular dynamics simulation. Western blotting and reverse transcription-quantitative polymerase chain reaction assays were used to assess protein and gene expression levels of P21, BIM, and PPARγ downstream of FoxO1 in SH-SY5Y cells, respectively. Western blotting and enzyme-linked immunoassays were performed to explore the effect of FoxO1 agonists on APP metabolism. RESULTS: N-(3-methylisothiazol-5-yl)-2-(2-oxobenzo[d]oxazol-3(2H)-yl) acetamide (compound D) had the highest affinity for FoxO1. Compound D activated FoxO1 and regulated the expression of its downstream target genes, P21, BIM, and PPARγ. In SH-SY5Y cells treated with compound D, BACE1 expression levels were downregulated, and the levels of Aß1-40 and Aß1-42 were also reduced. CONCLUSIONS: We present a novel small-molecule FoxO1 agonist with good anti-AD effects. This study highlights a promising strategy for new drug discovery for AD.

Physalin B reduces Aß secretion through down-regulation of BACE1 expression by activating FoxO1 and inhibiting STAT3 phosphorylation.

Physalin B (PB), one of the major active steroidal constituents of Solanaceae Physalis plants, has a wide variety of biological activities. We found that PB significantly down-regulated ß-amyloid (Aß) secretion in N2a/APPsw cells. However, the underlying mechanisms are not well understood. In the current study, we investigated the changes in key enzymes involved in ß-amyloid precursor protein (APP) metabolism and other APP metabolites by treating N2a/APPsw cells with PB at different concentrations. The results indicated that PB reduced Aß secretion, which was caused by down-regulation of ß-secretase (BACE1) expression, as indicated at both the protein and mRNA levels. Further research revealed that PB regulated BACE1 expression by inducing the activation of forkhead box O1 (FoxO1) and inhibiting the phosphorylation of signal transducer and activator of transcription 3 (STAT3). In addition, the effect of PB on BACE1 expression and Aß secretion was reversed by treatment with FoxO1 siRNA and STAT3 antagonist S3I-201. In conclusion, these data demonstrated that PB can effectively down-regulate the expression of BACE1 to reduce Aßsecretion by activating the expression of FoxO1 and inhibiting the phosphorylation of STAT3.

Alterations of fatty acid composition and metabolism in APP/PS1 transgenic mice.

Accumulating evidence suggests that abnormal fatty acid composition is related to the development of Alzheimer's disease (AD). However, there is no consistency in the fatty acid profile and metabolism associated with AD pathogenesis. This study aims to define the characteristics of fatty acid composition and metabolism in AD. Using 6-month-old APP/PS1 transgenic mice with wild-type mice as a control, we examined the serum lipids, brain fatty acid composition, and the expression levels of various genes involved in liver fatty acid ß-oxidation. The results of our study demonstrate that APP/PS1 mice present decreased serum free fatty acids, altered brain fatty acid profiles, and minimal change in liver fatty acid ß-oxidation. Our results suggest that abnormal fatty acid compositions and contents may play potential roles in AD progression. This study provides further evidence for the metabolic basis of AD pathogenesis.

FoxO1 overexpression reduces Aß production and tau phosphorylation in vitro.

Forkhead box O1 (FoxO1), a key molecule in the regulation of cell growth, differentiation and metabolism, is an important transcription factor. However, the effect of FoxO1 on Alzheimer's disease (AD) needs further investigation. In this study, we aimed to explore the function and mechanism of FoxO1 in amyloid-ß (Aß) production and tau phosphorylation in AD. First, compared with the age matched wild-type (WT) mice, we showed that FoxO1 protein levels were reduced in the cortices but nearly unchanged in the hippocampi of 6-month-old APPswe/PSEN1dE9 transgenic mice expressing Swedish APP and Presenilin1 delta exon 9 mutations (APP/PS1 mice). Then, we found that overexpression of FoxO1 significantly attenuated Aß production through inhibiting the amyloidogenic processing of ß-amyloid precursor protein (APP), mediated by the key enzymes BACE1 and PS1, in N2a/APPsw cells. Furthermore, in FoxO1-overexpressing HEK293/Tau cells, the decreased levels of tau phosphorylation at selective sites (S262 and T231) were accompanied by increasing the expression of p-GSK-3ß (S9), and reducing p-ERK. In contrast, the total tau (Tau-5), non-phosphorylated tau (Tau-1), p-Tau (S404), CDK5 and PP2A levels remained unchanged. These findings indicate that FoxO1 is related to AD and suggest FoxO1 as a therapeutic target for AD that reduces the levels of both Aß expression and tau phosphorylation.

Effects of chain length of saturated fatty acids on Aß generation in SH-SY5Y cells.

Many studies have shown that saturated fat diet increases the risk of AD. Recently saturated very long chain fatty acids (VLCFAs) have been found be accumulated in AD patients. The variety of saturated fatty acids are found in the diets and human bodies. However, it is not clear which one or more fatty acids are involved in AD pathogenesis. This study investigated the effects of three saturated fatty acids with different carbon chain length (C16:0, C20:0, and C26:0) on amyloid precursor protein (APP) processing and amyloid-ß peptide (Aß) generation. Here, SH-SY5Y cells were treated with vehicle, C16:0, C20:0, and C26:0 (10 µmol/L, 24 h). Compared to the vehicle, C16:0 did not cause any significantly change in APP processing and Aß generation. C20:0 and C26:0 increased Aß levels and the expressions of APP, ß- and γ-secretase and decreased the expression of α-secretase, and C26:0 had the strongest effects among three fatty acids. Moreover, C20:0 and C26:0 significantly increased reactive oxygen species (ROS), and C16:0 had no such effect. These data indicate that saturated fatty acids with different carbon chain length (C16:0, C20:0 and C26:0) have different effects on the process of Aß generation, and fatty acids with longer chain (C20:0 and C26:0) have more potential to promote Aß production and an underlying mechanism of fatty acids action may be related to the elevated oxidative stress. This work supports saturated very long chain fatty acids may play a potential role in the pathogenesis of AD.

Effect of TCDD on the fate of epithelial cells isolated from human fetal palatal shelves (hFPECs).

Cleft palate is caused by the failure of palatal midline epithelial cells to disintegrate, which is necessary for palatal mesenchymal confluence. Although 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exposure is linked to cleft palate at a high rate, the mechanism remains to be elucidated. The present study was designed to determine the effects of TCDD on the fate of epithelial cell isolated from human fetal palatal shelves (hFPECs). We demonstrate that TCDD increased cell proliferation and promoted the progression of cells from G1 to S phase as well as increased the number of cells entering the G2/M phase. We found that TCDD has no measurable effect on apoptosis of hFPECs. The protein level assays revealed that TCDD increased cyclin-dependent kinases 4 (cdk4), cyclin D1, cyclin E and p21 (Waf1/Cip1) but not cdk2, bcl-2, cyclin B1 and cyclin A. Furthermore, TCDD activated PI3K/AKT signaling, and the PI3K inhibitor, LY294002, partially abrogated TCDD-induced cell proliferation and gene modulations. TCDD treatment increased CYP1A1 mRNA and protein levels, which indicated the activation of AhR signaling. Knockdown of the AhR with siRNA suppressed TCDD-induced cell proliferation and PI3K/AKT signaling activation. Taken together, these data demonstrated that TCDD is able to promote growth of hFPECs through AhR-dependent activation of the PI3K/AKT pathway, which may account for the underlying mechanism by which TCDD causes a failure of palatal fusion.

TCDD promoted EMT of hFPECs via AhR, which involved the activation of EGFR/ERK signaling.

One critical step of second palatal fusion is the newly formed medial epithelia seam (MES) disintegration, which involves apoptosis, epithelial to mesenchymal transition (EMT), and cell migration. Although the environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) produces cleft palate at high rates, little is known about the effects of TCDD exposure on the fate of palatal epithelial cells. By using primary epithelial cells isolated from human fetal palatal shelves (hFPECs), we show that TCDD increased cell proliferation and EMT, as demonstrated by increased the epithelial markers (E-cadherin and cytokeratin14) and enhanced the mesenchymal markers (vimentin and fibronectin), but had no effect on cell migration and apoptosis. TCDD exposure led to a dose-dependent increase in Slug protein expression. Coimmunoprecipitation revealed that TCDD promoted AhR to form a protein complex with Slug. ChIP assay confirmed that TCDD exposure recruited AhR to the xenobiotic responsive element of Slug promoter. Knockdown of AhR by siRNA remarkably weakened TCDD-induced binding of AhR to the XRE promoter of slug, thereby suppressed TCDD-induced vimentin. Further experiment showed that TCDD stimulated EGFR phosphorylation did not influence the TGFß3/Smad signaling; whereas TCDD increased phosphorylation of ERK1/2 and p38 with no effect on activation of JNK. By using varieties of inhibitors, we confirmed that TCDD promoted proliferation and EMT of hFPECs via activation of EGFR/ERK pathway. These data make a novel contribution to the molecular mechanism of cleft palate by TCDD.

Progesterone inhibits the expression of cycloxygenase-2 and interleukin-1ß in neonatal rats with hypoxic ischemic brain damage.

Recent studies found that progesterone (PROG) has a noticeable preventive effect on brain injuries. However, the underlying mechanisms of these effects, particularly on hypoxic ischemic brain damage (HIBD), remain unclear. This study observed the influence of PROG on the expression of cycloxygenase-2 (COX-2) and interleukin-1ß (IL-1ß) in HIBD neonatal rats, and explored the corresponding molecular mechanisms underlying the neuroprotective effect of PROG. Sixty 7-day-old neonatal Wistar rats were divided into sham operation (control), hypoxic ischemia (HI), and drug prophylaxis (PROG) groups, and HIBD animal models were routinely established. The PROG group was intraperitoneally injected with 0.5 g/L PROG at a dosage of 8 mg/kg 30 min before establishment of the model. All the animals were sacrificed 24 h after modeling. Changes in the COX-2 and IL-1ß contents in the brain tissues were determined using enzyme-linked immunosorbent assay. Protein expression was observed using immunohistochemistry, and mRNA expression was determined using reverse transcription polymerase chain reaction. The expression and contents of COX-2 and IL-1ß in the HI group were significantly higher than those in the control group (P < 0.01). Compared with the HI group, the PROG group showed noticeably lower expression and contents of COX-2 and IL-1ß (P < 0.05). In conclusion, PROG can inhibit the expression of COX-2 and IL-1ß in brain tissue, further reducing the level of COX-2 and IL-1ß, which may be one of the mechanisms for protection from HIBD.

Decreased liver peroxisomal ß-oxidation accompanied by changes in brain fatty acid composition in aged rats.

Peroxisomal ß-oxidation is primarily responsible for the degradation of very long chain fatty acids (VLCFAs), dicarboxylic acids, unsaturated fatty acids and branched fatty acids. The genes encoding ß-oxidation enzymes are transcriptionally regulated by peroxisome proliferator-activated receptor alpha (PPARα). Age-related decreases in acyl-CoA oxidase 1 (ACOX1) activity, a key enzyme involved in peroxisomal ß-oxidation, have been found in aged rodents. To determine whether decreased peroxisomal ß-oxidation with aging affects brain fatty acid composition, 22-month-old (old) and 3-month-old (young) male Sprague-Dawley rats were used. We confirmed the decreased expression of liver ACOX1 and PPARα in old rats. In addition, a gas chromatography assay showed significant changes in the percentage of fatty acids in the cerebral cortices between old and young rats. In the cerebral cortices of old rats, the increased fatty acids included VLCFAs (C20:0, C22:0, C24:0) and monounsaturated fatty acids (C16:1, C18:1, C20:1, C22:1, C24:1), whereas the decreased fatty acids included C18:0, C20:4 and C22:6. These results indicated that decreased liver peroxisomal ß-oxidation was accompanied by changes in brain fatty acid composition with aging and suggested that peroxisomal ß-oxidation dysfunction may play a potential role in the progression of brain aging.

[Mechanism of MBL inhibiting the LPS-induced DC maturation].

The study was aimed to investigate the mechanism of mannan-binding lectin (MBL) on bacterial lipopolysaccharide (LPS)-induced human peripheral blood monocyte-derived dendritic cell (DC) maturation. The monocytes were prepared from the peripheral blood of healthy adult volunteers. The immature dendritic cells (imDC) were induced by 5-day-culture in medium supplemented with rhGM-CSF and rhIL-4. FACS was used to investigate the interaction of MBL with imDC and the impact of MBL on LPS binding to imDC. ELISA and Western blot was used to analyze the interaction of MBL with soluble TLR4 ectodomain protein (sTLR4); Western blot was used to detect LPS-induced NF-κB translocation in imDC. The results showed that MBL could directly bind to imDC in the presence of calcium. sTLR4 protein or LPS could competitively inhibit the binding of MBL to imDC. ELISA and Western blot showed that MBL could evidently bind to sTLR4 protein in a concentration-dependent manner. FACS showed that MBL could competitively inhibit the binding of LPS to imDC by binding to imDC directly. Western blot showed that MBL decreased LPS-induced NF-κB translocation in imDC. It is concluded that MBL may competitively inhibit the binding of LPS to imDC by binding to TLR4 expressed on imDC, resulted in inhibition of LPS-induced DC maturation, suggesting that MBL can regulate DC maturation through ligand-binding. This study provides the good foundation to clarify the mechanism of MBL inhibiting the LPS-induced DC maturation.

[Effect of recombinant human growth hormone on the secretion of TNF-α and IL-6 by THP-1 cells and its correlation with the NF-κB pathway].

OBJECTIVE: To investigate the effect of recombinant human growth hormone (rhGH) on the secretion of TNF-α and IL-6 in THP-1 cells and analyze the correlation between the secretion and NF-κB signaling pathway. METHODS: The concentrations of TNF-α and IL-6 in the supernatants of THP-1 induced by rhGH were measured with ELISA. The effects of LPS and an NF-κB inhibitor, BAY11-7082 on the secretion of TNF-α and IL-6 were also observed. The activity of NF-κB was detected by luciferase reporter and electrophoretic mobility shift assay (EMSA) in THP-1 cells induced by rhGH. RESULTS: rhGH alone promoted the secretion of TNF-α and IL-6 in THP-1 cells while inhibited the secretion of TNF-α and IL-6 in THP-1 stimulated by LPS. BAY11-7082 inhibited the secretion of TNF-α and IL-6 in THP-1 stimulated by LPS and rhGH. The activity of NF-κB was significantly correlated with the secretion of TNF-α and IL-6. CONCLUSION: rhGH played a bidirectional role in the regulation on the secretion of TNF-α and IL-6 via NF-κB signaling pathway in THP-1 cells.

Inhibition of peroxisomal ß-oxidation by thioridazine increases the amount of VLCFAs and Aß generation in the rat brain.

Alzheimer's disease (AD) is characterized by the accumulation of the ß-amyloid peptide (Aß), which is generated from sequential cleavages of the amyloid precursor protein (APP) by ß-secretase (BACE1) and γ-secretase. Fatty acid alterations in AD brains have recently received substantial attention. Because increased very long chain fatty acid (VLCFA) levels in AD brains imply that peroxisomal ß-oxidation dysfunction may be associated with AD pathogenesis, we investigated the effects of impaired peroxisomal ß-oxidation on Aß generation in vivo and in vitro using thioridazine, a selective peroxisomal ß-oxidation inhibitor. Under the experimental conditions, thioridazine caused VLCFA accumulation and increases in Aß(40) content, APP immunoreactivity and APP(751+770) mRNA expressions in the rat cerebral cortex. A correlation analysis showed that the Aß(40) levels were positively correlated with the cortex C(24:0) and C(26:0) levels. Additionally, the primary cerebral cortex neurons treated with this compound showed increases in APP(751+770) mRNA, APP protein, BACE1 mRNA and protein, and secreted Aß40 levels. This work supports an emerging viewpoint that impaired peroxisomal function may play an important role in the progression of AD pathology.

[Effects of activation of liver X receptor and peroxisome proliferator-activated receptor alpha on bile acid synthesis in rats].

OBJECTIVE: To explore the effects of the simultaneous activation of liver X receptor (LXR) and peroxisome proliferator-activated receptor alpha (PPARalpha) on bile acid biosynthesis in rats. METHODS: Totally 36 male SD rats were divided into three groups with 12 rats in each group: control group, high cholesterol (HC) group, and high cholesterol + fenofibrate (HC + FENO) group. Total bile acids (serum bile acids plus fecal bile acids) level was assayed. The levels of mRNA for peroxisomal palmitoyl-CoA oxidase (Acox1), LXR, cholesterol 7alpha-hydroxylase (CYP7A1), D-bifunctional protein (DBP), trihydroxycoprostanoyl-CoA oxidase (Acox2), sterol 12alpha-hydroxylase (CYP8B1), and sterol 27-hydroxylase (CYP27A1) in liver were detected by RT-PCR. RESULTS: Total bile acid level was significantly higher in HC + FENO group than in HC group (P < 0.01), and both were significantly higher than that in control group (P < 0.01). Compared with HC group, the mRNA expression of Acox1 and DBP was significantly higher in HC + FENO group (P < 0.01), but no statistical differences was found between HC group and control group. The mRNA levels of LXR and CYP7A1 in HC + FENO group and HC group were not significantly different but were both significantly higher than that in control group (P < 0.01, P < 0.05). No changes were observed in Acox2, CYPSB1, and CYP27A1 mRNA levels among these three groups. CONCLUSION: Simultaneous activation of LXR and PPARalpha can increase of CYP7A1 and DBP mRNA exDression and thus accelerates the biosynthesis of bile acid.

[Relationship between the increase of hepatic D-bifunctional protein activity and bile acid biosynthesis in rats].

OBJECTIVE: To determine the physiological role of D-bifunctional protein (DBP) in bile acid biosynthesis through investigating the effect of increasing activity of DBP on bile acid biosynthesis. METHODS: Twenty male Wistar rats were divided into two groups: diethylhexyl phthalate (DEHP) group (n = 10) and control group (n = 10). Serum triglyceride, total cholesterol, hepatic DBP activity, and fecal bile acids were assayed. The mRNA levels of hepatic peroxisome proliferator-activated receptor alpha (PPARalpha), DBP, and cholesterol 7alpha-hydroxylase (CYP7A1) were detected by RT-PCR. RESULTS: Compared with control group, serum triglyceride level was decreased significantly and PPARalphamRNA level was increased significantly in DEHP group (P < 0.01). Together with a sharp induction of DBP mRNA expression and DBP activity in DEHP group (P < 0.01), the levels of CYP7A1 mRNA and fecal bile acids were significantly increased by 1.9 times and 1.6 times respectively compared to control group (P < 0.01). There was a significantly positive correlation between DBP mRNA level or DBP activity and CYP7A1 mRNA level (r = 0.89, P < 0.01; r = 0.95, P < 0.01). CONCLUSION: The up-regulation of DBP mRNA and activity in liver can result in the increase in CYP7A1 mRNA expression and bile acid biosynthesis, suggesting that DBP may be involved in bile acid biosynthesis together with CYP7A1.