Sclareol protected against intestinal barrier dysfunction ameliorating Crohn's disease-like colitis via Nrf2/NF-B/MLCK signalling

BACKGROUND

Inflammation-induced intestinal barrier dysfunction is not only a pathological feature of Crohn's disease (CD) but also an important therapeutic target. Sclareol (SCL) is a nontoxic natural plant compound with anti-inflammatory effect, but its role in CD has not been established.

METHODS

In vivo studies of mice with TNBS-induced colitis were carried out to evaluate the effects of SCL on CD-like colitis and intestinal barrier function. In vitro, a TNF-α-induced colonic organoid model was established to test the direct effect of SCL on inflammation-induced intestinal barrier injure and inflammatory response. The Nrf2/NF-κB/MLCK signalling was analysed to explore the mechanism of SCL.

RESULTS

In vivo, SCL largely alleviated the colitis in TNBS mice, as evidenced by improvements in the weight loss, colitis symptoms, endoscopic score, macroscopic histological score, and histological inflammation score. Moreover, SCL significantly improved intestinal barrier dysfunction, manifested as reduced intestinal permeability and decreased intestinal bacterial translocation in TNBS mice. Importantly, SCL antagonised the intestinal mucosal inflammation while protecting tight junctions in TNBS mice. In vitro, SCL largely depressed pro-inflammatory cytokines levels and improved intestinal epithelial permeability in a TNF-α-induced colonic organoid model. In the context of CD, the protective effects of SCL against inflammation and intestinal barrier damage are at least partially results from the Nrf2 signalling activation and the NF-κB/MLCK signalling inhibition.

CONCLUSIONS

SCL improved intestinal barrier dysfunction and alleviated CD-like colitis, possibly through modulation of Nrf2/NF-κB/MLCK signalling. In view of SCL's safety profile, there is hope that it will be useful in the clinic.

Hemisynthesis and cytotoxic evaluation of manoyl oxide analogs from sclareol: effect of two tertiary hydroxyls & Heck coupling on cytotoxicity

Sclareol, a bioactive diterpene alcohol isolated from Salvia sclarea, was subjected to structural modification and cytotoxic evaluation. Boron-Heck-coupled analogs of manoyl oxide were prepared from sclareol in a two-step reaction scheme. In the first step manoyl oxide was prepared from sclareol using cerium (IV) ammonium nitrate. Further the structural modification of manoyl oxide via Palladium (II) catalysed Boron-Heck coupling reaction produced a new series of compounds. All the synthesised compounds were screened for in vitro cytotoxic evaluation against four cancer cell lines HCT-116, MCF-7, MDA-MB231and MDA-MB468. The results showed that manoyl oxide is less active than sclareol. Sclareol shows an IC50 of 2.0 µM compared to manoyl oxide with an IC50 of 50 µM against the MCF-7 cell line. From the results it was inferred that the presence of two tertiary hydroxyls in sclareol are necessary for its cytotoxic activity and Heck coupled analogs are more active than sclareol and manoyl oxide.

The potential of R. toruloides mevalonate pathway genes in increasing isoprenoid yields in S. cerevisiae: Evaluation of GGPPS and HMG-CoA reductase

The enzymes of the mevalonate pathway need to be improved to achieve high yields of isoprenoids in the yeast Saccharomyces cerevisiae. The red yeast Rhodosporidium toruloides produces high levels of carotenoids and may have evolved to carry a naturally high flux of isoprenoids. Enzymes from such yeasts are likely to be promising candidates for improvement. Towards this end, we have systematically investigated the various enzymes of the mevalonate pathway of R. toruloides and custom synthesized, expressed, and evaluated six key enzymes in S. cerevisiae. The two nodal enzymes geranyl pyrophosphate synthase (RtGGPPS) and truncated HMG-CoA reductase (RttHMG) of R. toruloides showed a significant advantage to the cells for isoprenoid production as seen by a visual carotenoid screen. These two were analyzed further, and attempts were also made at further improvement. RtGGPPS was confirmed to be superior to the S. cerevisiae enzyme, as seen from in vitro activity determinations and in vivo production of the heterologous diterpenoid sclareol. Four mutants were created through rational mutagenesis but were unable to improve the activity further. In the case of RttHMG, functional evaluation of the enzyme revealed that it was very unstable despite functioning very well in S. cerevisiae. We succeeded in stabilizing the enzyme through mutation of a conserved serine in the catalytic region, which did not alter the enzyme activity per se. In vivo evaluation of the mutant revealed that it could enable better sclareol yields. Therefore, these two enzymes from the red yeast are excellent candidates for heterologous isoprenoid production.

Sclareol induces cell cycle arrest and ROS-mediated apoptosis and ferroptosis in lung adenocarcinoma cells

Sclareol (SC) has shown significant anticancer activity against breast and colon cancers among others. However, its ability to precipitate similar anticancer effects in lung cancer has yet to be investigated. To address this issue, SC-treated lung adenocarcinoma cells (A549) were assessed for viability and functional competence as well as the expression of genes related to apoptosis and cell cycling. Our results demonstrated that SC treatment inhibited A549 cell clonogenic features and reduced their migration and invasion potential in a dose-dependent manner. Mechanistically, SC treatment downregulated the expression of cyclin D1 and survivin and upregulated that of p21 and p16, which was associated with a significant increase in the percentage of SubG0 cells. SC treatment is also associated with the induction of both the extrinsic and intrinsic apoptotic pathways, as evidenced by the increased expression and splitting of PARP1 and procaspases 3 and 9 and the reduced expression of antiapoptotic proteins Bcl-2 and Bcl-xL. Increased cell death in SC-treated cells is likely to have resulted from the induction of ferroptosis as suggested by the reduced expression of FPN and the inhibition of the anti-ferroptosis regulator GPX4. In conclusion, the data presented here suggest that SC can reduce lung carcinoma cell growth and metastasis and promote cell death.

Sclareol exerts synergistic antidepressant effects with quercetin and caffeine, possibly suppressing GABAergic transmission in chicks

This study evaluated the effects of sclareol (SCL) with or without caffeine (CAF) and quercetin (QUR) using in-vivo and in-silico studies. For this, 5-day-old chicks weighing between 45 and 48 g were randomly divided into five groups and treated accordingly. The chicks were monitored to compare the occurrence, latency, and duration of sleep as well as the loss and gain of righting reflex in response to SCL-10 mg/kg, CAF-10 mg/kg, and QUR-50 mg/kg using a thiopental sodium (TS)-induced sleeping model. Data were analyzed by one-way ANOVA followed by t-Student-Newman-Keuls' as a posthoc test at 95% confidence intervals with multiple comparisons. An in-silico study was also performed to investigate the possible antidepressant mechanisms of the test and/or standard drugs with different subunits of GABAA receptors. In comparison to the SCL, CAF, and QUR individual groups, SCL+CAF+QUR significantly increased the latency while decreasing the length of sleep. The incidence of loss and gain of the righting reflex was also modulated in the combination group. SCL showed better interaction with GABAA (α2 and α5) subunits than QUR with α2, α3, and α5. All these compounds showed stronger interactions with the GABAA receptor subunits than the standard CAF. Taken together, SCL, CAF, and QUR reduced the TS-induced righting reflex and sleeping time in the combination group more than in the individual treatments. SCL may show its antidepressant effects, possibly through interactions with GABAA receptor subunits.

Antiemetic effects of sclareol, possibly through 5-HT3 and D2 receptor interaction pathways: In-vivo and in-silico studies

BACKGROUND

Emesis is a complex physiological phenomenon that serves as a defense against numerous toxins, stressful situations, adverse medication responses, chemotherapy, and movement. Nevertheless, preventing emesis during chemotherapy or other situations is a significant issue for researchers. Hence, the majority view contends that successfully combining therapy is the best course of action. In-vivo analysis offers a more comprehensive grasp of how compounds behave within a complex biological environment, whereas in-silico evaluation refers to the use of computational models to forecast biological interactions.

OBJECTIVES

The objectives of the present study were to evaluate the effects of Sclareol (SCL) on copper sulphate-induced emetic chicks and to investigate the combined effects of these compounds using a conventional co-treatment approach and in-silico study.

METHODS

SCL (5, 10, and 15 mg/kg) administered orally with or without pre-treatment with anti-emetic drugs (Ondansetron (ODN): 24 mg/kg, Domperidone (DOM): 80 mg/kg, Hyoscine butylbromide (HYS): 100 mg/kg, and Promethazine hydrochloride (PRO): 100 mg/kg) to illustrate the effects and the potential involvement with 5HT3, D2, M3/AChM, H1, or NK1 receptors by SCL. Furthermore, an in-silico analysis was conducted to forecast the role of these receptors in the emetic process.

RESULTS

The results suggest that SCL exerted a dose-dependent anti-emetic effect on the chicks. Pretreatment with SCL-10 significantly minimized the number of retches and lengthened the emesis tendency of the experimental animals. SCL-10 significantly increased the anti-emetic effects of ODN and DOM. However, compared to the ODN-treated group, (SCL-10 + ODN) group considerably (p < 0.0001) extended the latency duration (109.40 ± 1.03 s) and significantly (p < 0.01) decreased the number of retches (20.00 ± 0.70), indicating an anti-emetic effect on the test animals. In in-silico analysis, SCL exhibited promising binding affinities with suggesting receptors.

CONCLUSION

SCL-10 exerted an inhibitory-like effect on emetic chicks, probably through the interaction of the 5HT3 and D2 receptors. Further studies are highly appreciated to validate this study and determine the precise mechanism(s) behind the anti-emetic effects of SCL. We expect that SCL-10 may be utilized as an antiemetic treatment in a single dosage form or that it may function as a synergist with other traditional medicines.

Novel hybrids of sclareol and 1,2,4-triazolo[1,5-a]pyrimidine show collateral sensitivity in multidrug-resistant glioblastoma cells

The synthesis of 24 hybrid molecules, consisting of naturally occurring sclareol (SCL) and synthetic 1,2,4-triazolo[1,5-a]pyrimidines (TPs), is described. New compounds were designed with the aim of improving the cytotoxic properties, activity, and selectivity of the parent compounds. Six analogs (12a-f) contained 4-benzylpiperazine linkage, while 4-benzyldiamine linkage was present in eighteen derivatives (12g-r and 13a-f). Hybrids 13a-f consist of two TP units. After purification, all hybrids (12a-r and 13a-f), as well as their precursors (9a-e and 11a-c), were tested on human glioblastoma U87 cells. More than half of the tested synthesized molecules, 16 out of 31, caused a significant reduction of U87 cell viability (more than 75% reduction) at 30 µM. The concentration-dependent cytotoxicity of these 16 compounds was also examined on U87 cells, corresponding multidrug-resistant (MDR) U87-TxR cells with increased P-glycoprotein (P-gp) expression and activity, and normal lung fibroblasts MRC-5. Importantly, 12l and 12r were active in the nanomolar range, while seven compounds (11b, 11c, 12i, 12l, 12n, 12q, and 12r) were more selective towards glioblastoma cells than SCL. All compounds except 12r evaded MDR, showing even better cytotoxicity in U87-TxR cells. In particular, 11c, 12a, 12g, 12j, 12k, 12m, 12n, and SCL showed collateral sensitivity. Hybrid compounds 12l, 12q, and 12r decreased P-gp activity to the same extent as a well-known P-gp inhibitor - tariquidar (TQ). Hybrid compound 12l and its precursor 11c affected different cellular processes including the cell cycle, cell death, and mitochondrial membrane potential, and changed the levels of reactive oxygen and nitrogen species (ROS/RNS) in glioblastoma cells. Collateral sensitivity towards MDR glioblastoma cells was caused by the modulation of oxidative stress accompanied by inhibition of mitochondria.

Efficient Biotransformation of Sclareol to Sclareolide by Filobasidium magnum JD1025

In this study, a newly isolated strain Filobasidium magnum JD1025 was investigated for its production of sclareolide, which was verified to be a valuable raw material in various industrial fields. Together with a comprehensive analysis of the genome sequence, effective fermentation method to convert sclareol to sclareolide via the isolated strain was explored and optimized by taking the selected co-solvent and nitrogen source into account. The results showed that the final conversion rate could be achieved at 88.79 ± 1.06% with the initial sclareol concentration of 30 g·L^-1 after 72 h in baffled flask. The corresponding yield concentration of sclareolide was 21.62 ± 0.26 g·L^-1 and the conversion rate per unit thallus attained to 6.11 ± 0.06 % g^-1·L^-1. Overall, the current study suggested a valid method for the application of Filobasidium magnum JD1025 as bio-transformer to produce sclareolide from sclareol.

Sclareol attenuates angiotensin II-induced cardiac remodeling and inflammation via inhibiting MAPK signaling

Chronic inflammation plays an important role in hypertensive heart failure. Suppressing angiotensin II (Ang II)-induced cardiac inflammation may contribute to the treatment of hypertension-associated heart failure. Sclareol, a natural product initially isolated from the leaves and flowers of Salvia sclarea, possesses antiinflammatory and immune-regulation activity in various systems. However, its effect on Ang II-induced cardiac remodeling remains unknown. In this study, we have explored the potential effects of sclareol on Ang II-induced heart failure. In vivo experiments were conducted in mice with Ang II-pump infusion for 28 days. Sclareol administration at 5 mg·kg-1 ·d-1 significantly reduced the expression of myocardial injury markers. Sclareol also exerts protective effects against Ang II-induced cardiac dysfunction in mice which is associated with alleviated cardiac inflammation and fibrosis. Transcriptome analysis revealed that inhibition of the Ang II-activated mitogen-activated protein kinase (MAPK) pathway contributed to the protective effect of sclareol. Sclareol inhibits Ang II-activated MAPKs pathway to reduce inflammatory response in mouse hearts and cultured cardiomyocytes. Blockage of MAPKs in cardiomyocytes abolished the antiinflammatory effects of sclareol. In conclusion, we show that sclareol protects hearts against Ang II-induced injuries through inhibiting MAPK-mediated inflammation, indicating the potential use of sclareol in the prevention of hypertensive heart failure.

Sclareol ameliorates liver injury by inhibiting nuclear factor-kappa B/NOD-like receptor protein 3-mediated inflammation and lipid metabolism disorder in diabetic mice

Objectives: Sclareol (SCL) is a natural diterpene with anti-inflammation and antioxidant properties. This study aimed to assess the hepatoprotective effects of SCL in diabetic mice. Methods: SCL (10 mg/kg) was administered intragastrically to C57BL/6 mice with streptozotocin-induced diabetes daily for 5 weeks to evaluate its beneficial effects in liver injury. Body and liver weight and blood glucose levels were measured. Liver histopathology, fibrosis, and lipid accumulation were evaluated using hematoxylin and eosin, Masson's trichrome, and Oil Red O staining, respectively. Serum hepatic enzyme and lipid levels were measured using an automatic biochemical analyzer. Hepatocellular apoptosis was measured using the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. Oxidative stress markers and reactive oxygen species (ROS) were measured using appropriate assay kits. The effects of sclareol on inflammation and lipid metabolism was evaluated by enzyme-linked immunosorbent assay (ELISA), immunohistochemical analysis, and Western blot assays. Results: SCL significantly decreased serum liver enzymes and lipids levels, and alleviated adipogenesis and fibrosis. Moreover, the protein levels of acetyl-CoA carboxylase and sterol response element-binding protein 1 were downregulated, whereas the expression of carnitine palmitoyl transferase 1 was upregulated. SCL increased the antioxidant activity, and decreased ROS levels. SCL alleviated hepatic mitochondrial damage. Furthermore, SCL inhibited Kupffer cell infiltration and reduced serum inflammatory cytokine levels. SCL significantly downregulated the protein expression of nuclear factor-kappa B (NF-κB) P65, NOD-like receptor protein 3 (NLRP3), caspase 1, and interleukin-1β. Conclusions: Our findings suggest that SCL improves diabetes-induced liver injury by alleviating the NF-κB/NLRP3-mediated inflammation and lipid metabolism disorder.

Microbial electrosynthesis from carbon dioxide feedstock linked to yeast growth for the production of high-value isoprenoids

The difficulty in producing multi-carbon and thus high-value chemicals from CO₂ is one of the key challenges of microbial electrosynthesis (MES) and other CO₂ utilization technologies. Here, we demonstrate a two-stage bioproduction approach to produce terpenoids (>C₂₀) and yeast biomass from CO₂ by linking MES and yeast cultivation approaches. In the first stage, CO₂ (C₁) is converted to acetate (C₂) using Clostridium ljungdahlii via MES. The acetate is then directly used as the feedstock to produce sclareol (C₂₀), β-carotene (C₄₀), and yeast biomass using Saccharomyces cerevisiae in the second stage. With the unpurified acetate-containing (1.5 g/L) spent medium from MES reactors, S. cerevisiae produced 0.32 ± 0.04 mg/L β-carotene, 2.54 ± 0.91 mg/L sclareol, and 369.66 ± 41.67 mg/L biomass. The primary economic analysis suggests that sclareol and biomass production is feasible using recombinant S. cerevisiae and non-recombinant S. cerevisiae, respectively, directly from unpurified acetate-containing spent medium of MES.

Ultrasound assisted facile synthesis of Boron-Heck coupled sclareol analogs as potential antibacterial agents against Staphylococcus aureus

AIM

To evaluate the antimicrobial capability of sclareol and its derivatives against Staphylococcus aureus and its Methicillin-resistant strain (MRSA).

METHODS AND RESULTS

A new series of Boron-Heck-coupled sclareol analogs were prepared by structural modifications at C-15 terminal double bond of sclareol using ultrasonication. The structural modifications were designed to keep the stereochemistry of all the five chiral centres of sclareol intact. A two-step reaction scheme consisting of Boron-Heck coupling of sclareol followed by Wittig reaction was carried out to produce novel sclareol congeners for antintimicrobial evaluation. Three compounds SAJ-1, SAJ-2 and SB-11 exhibited strong antibacterial activity against Staphylococcus aureus and Methicillin-resistant strain (MRSA) with MIC values between 3 to 11 μM. Among all the screened compounds, SAJ-1 and SAJ-2 showed the best anti-biofilm profiles against both the strains. Moreover SAJ-1 and SAJ-2 acted synergistically with streptomycin against S. aureus while creating varying outcomes in combination with ciprofloxacin, penicillin, and ampicillin. SAJ-1 also acted synergistically with ampicillin against S. aureus, while SB-11 showed synergism with ciprofloxacin against both pathogens. Moreover, SAJ-1 and SAJ-2 also inhibited staphyloxanthin production in S. aureus and MRSA and induced post-antibiotic effects against both pathogens.

CONCLUSIONS

It can be inferred that SAJ-1, SAJ-2 and SB-11 may act as potential chemical entities for the development of antibacterial substances. The study revealed that SAJ-1 and SAJ-2 are most suitable sclareol analogs for further studies towards the development of antibacterial substances.

SIGNIFICANCE AND IMPACT OF THE STUDY

SAJ-1, SAJ-2 and SB-11 show promising antibacterial properties against Staphylococcus aureus. Efforts should be made and more research should be done, utilising in vivo models to determine their efficacy as antibiotics.

SCLAREIN (SCLAREol contained in zeIN) nanoparticles: Development and characterization of an innovative natural nanoformulation

Sclareol is a labdane diterpene which carries on a broad range of biological activities. However, its poor water solubility and bioavailability are the foremost drawbacks that limit its application in therapeutics. The purpose of this investigation was to develop a natural nanoformulation made up of a biopolymer i.e. zein and sclareol in order to address this issue and to enhance the pharmacological efficacy of the drug. The sclarein nanoparticles (sclareol-loaded zein nanosystems) showed a typical monomodal pattern, characterized by a mean diameter of ~120 nm, a narrow size distribution and a surface charge of ~-30 mV. The evaluation of the entrapment efficiency and the drug-loading capacity of the nanosystems demonstrated the noteworthy ability of the protein matrix to hold sclareol while allowing a gradual release of the compound over time. The nanosystems increased the cytotoxicity of sclareol at a drug concentration of ≥5 μM with respect to the free compound after just 24 h incubation against various cancer cell lines. Indeed, the interaction of tritiated sclarein formulations with cells showed a time-dependent cell uptake of the nanosystems commencing as early as 1 h from the onset of incubation, favouring a significant decrease of the efficacious concentration of the drug.

GC-MS/MS method for determination and pharmacokinetics of sclareol in rat plasma after intravenous administration

Sclareol, mainly isolated from Salvia officinalis, has a variety of pharmacological effects. In this work, a sensitive and rapid gas chromatography-tandem mass spectrometry (GC-MS/MS) method was first developed and validated for the determination and pharmacokinetics of sclareol in rat plasma. The chromatographic seperation of biosamples was performed with an HP-5MS column. Ethyl acetate was selected as the solvent to extract analytes from rat plasma. The multiple reaction monitoring transitions for sclareol and dehydrocostuslactone (Internal Standard, IS) were m/z 177 → 121 and m/z 230 → 173, respectively. The intra- and inter- precision, accuracy, matrix effect, recovery and stability meet the method requirements for biological sample analysis. The lowest limit of quantification (LLOQ) of the developed method for sclareol determination was 20 ng/mL. After intravenous administration (5.0 mg/kg) of sclareol to the rats, its drug clearance (CLz) and elimination half-life (t1/2z) was 2.7 ± 1.3 L/h/kg and 6.0 ± 4.6 h, respectively. The apparent volume of distribution (Vz) was 21.4 ± 12.9 L/kg, which indicated that sclareol was mainly distributed in extracellular fluid. Our results provided useful information for the further pharmacological investigation and preclinical studies of sclareol.

Sclareol inhibits RANKL-induced osteoclastogenesis and promotes osteoblastogenesis through promoting CCN1 expression via repressing the MAPK pathway

Osteoclasts are crucial cellular components of bone and are the cause of various bone problems like osteoporosis. Various biological activities such as anti-tumorous, anti-inflammatory, antibacterial, and immunomodulatory function are influenced by Sclareol, as a natural diterpene compound. However, studies on the effect and mechanism of Sclareol on osteoporosis are rare. In the current research, the influence of Sclareol on osteoclastogenesis and osteoblastogenesis was targeted to be discovered in ovariectomy (OVX)-induced animal models and in vitro. The expression levels of osteoclast-related genes such as c-Fos, NFATc1, and CTSK were detected by RT-qPCR and western blotting to understand the inhibition of Sclareol on the creation of osteoclast. The influence of Sclareol on osteoblastogenesis and the expression of osteoblastogenic markers were also examined. Sclareol inhibited the osteoclastogenesis caused by receptor activator of nuclear factor-κB ligand (RANKL) which promoted osteoblastogenesis through upregulating the expression of cysteine-rich protein 61 (CYR61/CCN1), which is a matricellular protein of the CCN family. The p-ERK and p-P38 protein expression levels were considerably downregulated by Sclareol. Furthermore, CCN1 overexpression partially mimicked the inhibitory effect of Sclareol, while the opposite results were obtained after CCN1 silencing. Additionally, Sclareol protected against loss of bones in an osteoporosis mouse model generated by OVX. The acquired results indicated that Sclareol represses RANKL-induced osteoclastogenesis and promotes osteoblastogenesis via promoting the expression of CCN1 by constraining the mitogen-activated protein kinase (MAPK) pathway. Our findings proposed that for the avoidance and treatment of osteoclast-linked disorders, Sclareol is a potentially effective drug. A proposed model for mediated regulation of osteoclastogenesis and osteoblastogenesis by Sclareol. The basic model of the process by which Sclareol prevents osteoclastogenesis and promotes osteoblastogenesis. Sclareol may increase the expression of CCN1 through inhibiting the MAPK pathway, thereby inhibiting osteoclast differentiation and attenuating bone resorption. Sclareol represses the expression of c-Fos, which stimulates the formation of osteoclast. In contrast, Sclareol promotes osteoblast differentiation by upregulating Runx2 expression, thereby improving the formation of bones. Consequently, Sclareol protects against loss of bones by regulating the stability of bone makeover via inhibition of bone formation and stimulation of bone resorption. Graphical Headlights 1. Sclareol represses RANKL-induced osteoclastogenesis. 2. Sclareol promotes osteoblast differentiation. 3. Sclareol inhibits the MAPK pathway through induction of CCN1. 4. Sclareol protects against bone loss by regulating the balance of bone remodeling via inhibition of bone formation and stimulation of bone resorption.

Sclareol modulates free radical production in the retinal rod outer segment by inhibiting the ectopic f1fo-atp synthase

We have previously shown that the retinal rod outer segments (OS) produce reactive oxygen species in the function of illumination in vitro, establishing a relationship among the extra-mitochondrial oxidative phosphorylation and phototransduction. This source of oxidative stress in the OS can be modulated by polyphenols, acting as inhibitors of F₁F_o-ATP synthase. The present study aimed at exploring whether sclareol, a diterpene, interacts with F₁F_o-ATP synthase mitigating the light-induced free radical production in the rod OS. Characterization of bovine retinal sections was conducted by immunogold analysis. Reactive oxygen intermediates production, oxygen consumption, the activity of the four respiratory complexes and ATP synthesis were evaluated in purified bovine rod OS. Molecular docking analyses were also conducted. Sclareol reduced free radical production by light-exposed rod OS. Such antioxidant effect was associated with an inhibition of the respiratory complexes and oxygen consumption (OCR), in coupled conditions. Sclareol also inhibited the rod OS ATP synthetic ability. Since the inhibitor effect on respiratory complexes and OCR is not observed in uncoupled conditions, it is supposed that the modulating effect of sclareol on the ectopic oxidative phosphorylation in the rod OS targets specifically the F₁F_o-ATP synthase. This hypothesis is confirmed by the in silico molecular docking analyses, which shows that sclareol binds the F₁ moiety of ATP synthase with high affinity. In conclusion, a beneficial effect of sclareol can be envisaged as a modulator of oxidative stress in the photoreceptor, a risk factor for the degenerative retinal diseases, suggestive of its potential beneficial action also in vivo.

Sclareol ameliorated ERCC1-mediated cisplatin resistance in A549 human lung adenocarcinoma cells and a murine xenograft tumor model by suppressing AKT-GSK3β-AP1/Snail and JNK-AP1 pathways

Cisplatin-based chemotherapy is a common first-line regimen for treating non-small cell lung cancer (NSCLC). However, drug resistance is still a major problem. The purposes of this study were to evaluate whether sclareol can reverse cisplatin resistance and to investigate its possible mechanisms. A549 cells, the human NSCLC cells with inherent cisplatin resistance, were used to investigate synergistic effect of sclareol with cisplatin in cell proliferation and migration as well as its regulatory mechanisms in expression of excision repair cross-complementation group 1 (ERCC1), a cisplatin resistance-associated molecule. Nude mice bearing subcutaneous A549 tumors were applied to investigate synergistic activity of sclareol in anti-tumor. As comparing to the cisplatin alone group, the treatment of cisplatin combined with sclareol significantly suppressed survival rate and cell migration of A549 cells. Besides, sclareol also exhibited suppression in ERCC1 expression by inhibiting AKT-GSK3β-AP1/Snail and JNK-AP1 pathways. Furthermore, the experimental data from in vivo study also demonstrated that the combination group of cisplatin and sclareol showed the greatest anti-tumor activity, whose effect could be partially attributed to sclareol-mediated decrease in intratumoral level of ERCC1 protein. Accordingly, sclareol has potential as an adjuvant for the treatment in NSCLC patients with cisplatin resistance.

Effects of Sclareol Against Small Cell Lung Carcinoma and the Related Mechanism: In Vitro and In Vivo Studies

BACKGROUND/AIM

This study aimed to investigate the anticancer effects and potential mechanisms of sclareol in a human small cell lung carcinoma (SCLC) cell line.

MATERIALS AND METHODS

Cell viability was determined by the MTT assay. Cell cycle, apoptosis and caspase activity were evaluated by flow cytometry. Cell cycle and DNA damage related protein expression was determined by western blotting. In vivo evaluation of sclareol was carried out in xenografted tumor mice models.

RESULTS

Sclareol significantly reduced cell viability, induced G₁ phase arrest and subsequently triggered apoptosis in H1688 cells. In addition, this sclareol-induced growth arrest was associated with DNA damage as indicated by phosphorylation of H2AX, activation of ATR and Chk1. Moreover, in vivo evaluation of sclareol showed that it could inhibit tumor weight and volume in a H1688 xenograft model.

CONCLUSION

Sclareol might be a novel and effective therapeutic agent for the treatment of SCLC patients.

STAT3-mediated Apoptotic-enhancing Function of Sclareol Against Breast Cancer Cells and Cell Sensitization to Cyclophosphamide

Sclareol is an organic compound with potential anti-tumor effects against various cancer types. However, its precise molecular mechanism in the suppression of tumor growth has not been fully elucidated. In the present study, the anti-proliferative and apoptosis-inducing effects of sclareol with cyclophosphamide were investigated in breast cancer cells and the involvement of the JAK/STAT pathway was evaluated. For this purpose, MCF-7 breast cancer cells were cultured and treated with various concentrations of sclareol to determine its IC₅₀. Cell viability was measured by MTT assay and apoptosis was assessed by flow cytometric analysis of annexin V binding. Gene and protein expression were examined by real-time PCR and Western blotting, respectively. The activity of caspase enzymes was also measured. The results showed that sclareol significantly reduced cell viability and triggered cell death and its co-administration with cyclophosphamide enhanced its anti-cancer properties. Additionally, sclareol up-regulated the expression of p53 and BAX and reduced the expression of Bcl-2. Docking studies indicated an interaction between sclareol and STAT3 which was proved by attenuation of STAT3 phosphorylation after treatment of the cells with sclareol. Sclareol was also capable of suppressing the function of IL-6 in modulating the expression of apoptosis-associated genes. Altogether these data suggest the potential of sclareol as an anti-cancer agent and demonstrate that a combination of sclareol with cyclophosphamide might serve as an effective chemotherapeutic approach resulting in improvements in the treatment of breast cancer.

Discovery of sclareol and sclareolide as filovirus entry inhibitors

Filoviruses cause severe hemorrhagic fever in humans. Ebola virus (EBOV) is the most contagious filovirus. Although compassionate treatments have been used during the latest Ebola outbreak, novel anti-EBOV agents are still urgently needed. In this study, sclareol and sclareolide, two natural products in Salvia sclarea, were identified as EBOV entry inhibitors with EC₅₀s of 2.4 μmol/L and 8.0 μmol/L, respectively, through blocking the viral fusion process. Moreover, both compounds exhibited inhibitory effects on all tested filoviruses' entry, indicating their wide-spectrum activities against filoviruses. This study provides insights into the two natural products and their applications against filovirus infectious diseases.

Sclareol is a potent enhancer of doxorubicin: Evaluation of the free combination and co-loaded nanostructured lipid carriers against breast cancer

AIMS

In this work, it was sought to determine if there was synergism between doxorubicin (DOX), a well-known antineoplastic, and sclareol (SC), a diterpene from natural origin, in breast cancer treatment. Moreover, it was investigated if their co-loading in the same nanocarrier would result in a gain of activity and/or a toxicity diminishment.

MAIN METHODS

The synergism of the DOX:SC combination was evaluated in MDA-MB-231 and 4T1 cells. A nanostructured lipid carrier (NLC) co-encapsulating DOX and SC in their synergistic molar ratio was prepared and characterised, in terms of mean diameter, zeta potential, DOX encapsulation efficiency, small angle X-ray scattering, differential scanning calorimetry, and polarised light microscopy for further intravenous administration. The anticancer activity of the combination, free and encapsulated, was evaluated in 4T1-tumour bearing mice.

KEY FINDINGS

It was determined that DOX:SC combination at the molar ratio 1:1.9 presents better synergistic anticancer activity than the molar ratio 1:7.5 in vitro. DOX:SC-loaded NLC (NLC-DOX-SC) improved in vitro cytotoxic and in vivo antitumour activity compared to free DOX. Although NLC-DOX-SC and free DOX:SC, at the synergistic molar ratio, showed similar activity in the in vivo study, the free combination provoked body weight loss, behaviour alterations and haematological toxicity in the animals, while this was not observed for NLC-DOX-SC.

SIGNIFICANCE

This work shows that SC and DOX present synergistic anticancer activity for breast cancer treatment whereas NLC-DOX-SC was a feasible alternative to attain the benefits posed by DOX:SC combination but with none to fewer side effects.

Sclareol attenuates the development of atopic dermatitis induced by 2,4-dinitrochlorobenzene in mice

Context: Atopic dermatitis is a common chronic inflammatory skin disease affecting up to 20% of children and 1% of adults worldwide. Treatment of atopic dermatitis include corticosteroids and immunosuppressants, such as calcineurin inhibitors and methotrexate. However, these treatments often bring about adverse effects including skin atrophy, osteoporosis, skin cancer, and metabolic syndrome. Objective: In this study, we evaluated the therapeutic effects and mechanisms of sclareol, a natural diterpene, on atopic dermatitis (AD)-like skin lesions induced by 2,4-dinitrochlorobenzene (DNCB) in mice. Materials and methods: To evaluate the effect of sclareol in vivo model, BALB/c mice were repeatedly injected intraperitoneally with sclareol (50 and 100 mg/kg) in 2,4-dinitrochlorobenzene (DNCB)-induced AD-like murine model. Major assays were enzyme-linked immunosorbent assay, histological analysis, flow cytometry, western blot analysis. Results: Intraperitoneal administration of sclareol (50 and 100 mg/kg) significantly attenuated AD-like symptoms, such as serum IgE levels, epidermal/dermal hyperplasia, and the numbers of infiltrated mast cells. In addition, systemic sclareol treatments reduced local pro-inflammatory cytokine concentrations, including IL-6, IL-1b, TNF-a, IL-4, IFN-g, and IL-17A, on AD-like lesions. Furthermore, we demonstrated that sclareol also suppressed T cell activation and the capability of cytokine productions (IFN-g, IL-4 and IL-17A) in response to DNCB stimulation. By examining the skin homogenate, we found that sclareol inhibited the AD-like severity likely through suppressions of both NF-kB translocation and phosphorylation of the MAP kinase pathway. Discussion and conclusions: Cumulatively, our results indicate that sclareol induced anti-inflammatory effects against the atopic dermatitis elicited by DNCB. Thus, sclareol is worth of being further evaluated for its potential therapeutic benefits for the clinical treatment of AD.

Comparative proteomic analyses of Hyphozyma roseonigra ATCC 20624 in response to sclareol

Sclareol is an important intermediate for ambroxide synthesis industries. Hyphozyma roseonigra ATCC 20624 was the only reported strain capable of degrading sclareol to the main product of sclareol glycol, which is the precursor of ambroxide. To date, knowledge is lacking about the effects of sclareol on cells and the proteins involved in sclareol metabolism. Comparative proteomic analyses were conducted on the strain H. roseonigra ATCC 20624 by using sclareol or glucose as the sole carbon source. A total of 79 upregulated protein spots with a > 2.0-fold difference in abundance on 2-D gels under sclareol stress conditions were collected for further identification. Seventy spots were successfully identified and finally integrated into 30 proteins. The upregulated proteins under sclareol stress are involved in carbon metabolism and nitrogen metabolism, and replication, transcription, and translation processes. Eighteen upregulated spots were identified as aldehyde dehydrogenases, which indicating that aldehyde dehydrogenases might play an important role in sclareol metabolism. Overall, this study may lay the fundamentals for further cell engineering to improve sclareol glycol production.

Synthesis and Antifungal Activities of Drimane-Amide Derivatives from Sclareol

AIM AND OBJECTIVE

Plant diseases are caused by fungal pathogens lead to severe economic losses in many agriculture crops. And the increasing resistance of many fungi to commonly used antifungal agents necessitates the discovery and development of new fungicides. So this study was focused on synthesizing novel skeleton compounds to effectively control plant diseases.

MATERIALS AND METHODS

A series of drimane-amide derivatives were designed, synthesized by aminolysis reaction of amine with intermediate sclareolide which was prepared from sclareol. The structures of all the synthesized compounds were confirmed using 1H NMR, 13C NMR, and HRMS (ESI) spectroscopic data. Their in vitro antifungal activity were preliminarily evaluated by using the mycelium growth rate method against five phytopathogenic fungi: Botrytis cinerea, Glomerella cingulata, Alternaria alternate, Alternaria brassicae, and Fusarium graminearum.

RESULTS

23 target compounds were successfully obtained in yields of 52-95%. Compounds A2 and A3 displayed favorable inhibitory potency against B. cinerea, G. cingulata and A. brassicae with IC50 values ranging from 3.18 to 10.48 µg/mL. These two compounds displayed higher fungicidal activity than sclareol against all the tested phytopathogenic fungi, and were more effective than the positive control thiabendazole against A. alternate and A. brassicae. The structure-activity relationship studies of compounds A1-10 indicated that both the position and type of substituent on the phenyl ring had significant effects on antifungal activity.

CONCLUSION

The drimane-amide derivatives A2 and A3 were the most promising derivatives and should be selected as new templates for the potential antifungal agents.

Comparative proteomic analyses of Hyphozyma roseonigra ATCC 20624 in response to sclareol

Sclareol is an important intermediate for ambroxide synthesis industries. Hyphozyma roseonigra ATCC 20624 was the only reported strain capable of degrading sclareol to the main product of sclareol glycol, which is the precursor of ambroxide. To date, knowledge is lacking about the effects of sclareol on cells and the proteins involved in sclareol metabolism. Comparative proteomic analyses were conducted on the strain H. roseonigra ATCC 20624 by using sclareol or glucose as the sole carbon source. A total of 79 up-regulated protein spots with a >2.0-fold difference in abundance on 2-D gels under sclareol stress conditions were collected for further identification. Seventy spots were successfully identified and finally integrated into 30 proteins. The up-regulated proteins under sclareol stress are involved in carbon metabolism; and nitrogen metabolism; and replication, transcription, and translation processes. Eighteen up-regulated spots were identified as aldehyde dehydrogenases, which indicating that aldehyde dehydrogenases might play an important role in sclareol metabolism. Overall, this study may lay the fundamentals for further cell engineering to improve sclareol glycol production.

Extreme promiscuity of a bacterial and a plant diterpene synthase enables combinatorial biosynthesis

Diterpenes are widely distributed across many biological kingdoms, where they serve a diverse range of physiological functions, and some have significant industrial utility. Their biosynthesis involves class I diterpene synthases (DTSs), whose activity can be preceded by that of class II diterpene cyclases (DTCs). Here, a modular metabolic engineering system was used to examine the promiscuity of DTSs. Strikingly, both a bacterial and plant DTS were found to exhibit extreme promiscuity, reacting with all available precursors with orthogonal activity, producing an olefin or hydroxyl group, respectively. Such DTS promiscuity enables combinatorial biosynthesis, with remarkably high yields for these unoptimized non-native enzymatic combinations (up to 15mg/L). Indeed, it was possible to readily characterize the 13 unknown products. Notably, 16 of the observed diterpenes were previously inaccessible, and these results provide biosynthetic routes that are further expected to enable assembly of more extended pathways to produce additionally elaborated 'non-natural' diterpenoids.

Cell-based assay system for high-throughput screening of anti-photo-aging agents in fibroblast transfectants

The matricellular protein CCN1 is significantly elevated in acutely ultraviolet-irradiated human skin and negatively regulates collagen homeostasis by suppressing collagen synthesis and increasing collagen degradation. In this study, we established a stable cell line, termed CCN1-GFs, by transfection of the pAcGFP1-1-CCN1 promoter plasmid and examined its usefulness as a cell-based assay system for screening anti-aging ingredients. The promoter of the reporter plasmid pAcGFP1-1-CCN1 promoter was transfected into NIH3T3 cells using the Lipofectamine reagent. G418-resistant cells were selected and further cloned. To confirm whether AcGFP1-1-CCN1 promoter plasmid recombined in the NIH3T3 cells, the level of AcGFP1-1-CCN1 was measured by PCR analysis. To determine if NIH3T3 cells expressed the gene encoding green fluorescence protein in a CCN1 promoter-dependent manner, the reporter enzyme activities were assayed using a fluorimeter and flow cytometer. To determine if CCN1 inhibitor, which was selected through this system, exerted a direct effect on the downstream signal, mRNA expression of collagen1 and MMP1A was checked by using real-time PCR. UVB irradiation of CCN1-GFs resulted in increased CCN1 promoter activity. Treatment with retinoic acid, a CCN1 inhibitor, inhibited UV-induced CCN1 promoter activity. Subsequent use of this assay system to screen anti-aging ingredients revealed that CCN1-GFs treated with sclareol showed decreased levels of UVB-induced CCN1 expression. Sclareol attenuated UVB-induced photo-aging by an increase in collagen synthesis and decrease in MMP-1 activity.