Synthesis and melanin biosynthesis inhibitory activity of (+/-)-terrein produced by Penicillium sp. 20135

Protection against Lipopolysaccharide-Induced Endotoxemia by Terrein Is Mediated by Blocking Interleukin-1β and Interleukin-6 Production

Terrein is a fungal metabolite and has been known to exert anti-melanogenesis, anti-cancer, and anti-bacterial activities. However, its role in endotoxemia has never been investigated until now. In the present study, we examined the effect of terrein on lipopolysaccharide (LPS)-induced endotoxemia in mice and characterized the potential mechanisms of action. Treatment with terrein increased the survival of mice and decreased the production of inflammatory cytokines, including interleukin-1β (IL-1β) and interleukin-6 (IL-6) in an LPS-induced endotoxemia model. In addition, terrein suppressed the LPS-induced production of IL-1β and IL-6 in RAW 264.7 cells, a murine macrophage-like cell line, and the mRNA expression of IL-1β and IL-6 was also inhibited by terrein in LPS-stimulated RAW 264.7 cells. Further study demonstrated that terrein blocked LPS-induced phosphorylation of p65 subunit of nuclear factor (NF)/κB and the phosphorylation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) was also suppressed by terrein treatment. Collectively, these results suggest that terrein exerts a protective effect again LPS-induced endotoxemia in mice by blocking the production of inflammatory cytokines. Our results also suggest that the anti-inflammatory effect of terrein might be mediated, at least in part, by blocking the activation of NF-κB, JNK, and p38 MAPK signaling pathways.

Enhanced production of terrein in marine-derived Aspergillus terreus by refactoring both global and pathway-specific transcription factors

Background

Terrein, a major secondary metabolite from Aspergillus terreus, shows great potentials in biomedical and agricultural applications. However, the low fermentation yield of terrein in wild A. terreus strains limits its industrial applications.

Results

Here, we constructed a cell factory based on the marine-derived A. terreus RA2905, allowing for overproducing terrein by using starch as the sole carbon source. Firstly, the pathway-specific transcription factor TerR was over-expressed under the control of a constitutive gpdA promoter of A. nidulans, resulting in 5 to 16 folds up-regulation in terR transcripts compared to WT. As expected, the titer of terrein was improved in the two tested terR OE mutants when compared to WT. Secondly, the global regulator gene stuA, which was demonstrated to suppress the terrein synthesis in our analysis, was deleted, leading to greatly enhanced production of terrein. In addition, LS-MS/MS analysis showed that deletion of StuA cause decreased synthesis of the major byproduct butyrolactones. To achieve an optimal strain, we further refactored the genetic circuit by combining deletion of stuA and overexpression of terR, a higher terrein yield was achieved with a lower background of byproducts in double mutants. In addition, it was also found that loss of StuA (both ΔstuA and ΔstuA::OEterR) resulted in aconidial morphologies, but a slightly faster growth rate than that of WT.

Conclusion

Our results demonstrated that refactoring both global and pathway-specific transcription factors (StuA and TerR) provides a high-efficient strategy to enhance terrein production, which could be adopted for large-scale production of terrein or other secondary metabolites in marine-derived filamentous fungi.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01859-5.

Recent Advances in Isolation, Synthesis and Biological Evaluation of Terrein

Terrein is a small-molecule polyketide compound with a simple structure mainly isolated from fungi. Since its discovery in 1935, many scholars have conducted a series of research on its structure identification, isolation source, production increase, synthesis and biological activity. Studies have shown that terrein has a variety of biological activities, not only can inhibit melanin production and epidermal hyperplasia, but also has anti-cancer, anti-inflammatory, anti-angiopoietic secretion, antibacterial, insecticidal activities, and so on. It has potential application prospects in beauty, medicine, agriculture and other fields. This article reviews the process of structural identification of terrein since 1935, and summarizes the latest advances in its isolation, source, production increase, synthesis, and biological activity evaluation, with a view to providing a reference and helping for the in-depth research of terrein.

Targeting Delivery Nanocarriers for (+)-Terrein to Enhance Its Anticancer Effects

As a compound from marine fungi, (+)-terrein showed significant anticancer activity. In this study, (+)-terrein was extracted from the marine-derived fungus and showed significant cytotoxicity against cancer cells, especially in A549 cells. To enhance its anticancer effects, redox-responsive nanocarriers based on folic acid-chitosan decorating the mesoporous silica nanoparticles were designed to control (+)-terrein target delivery into cancer cells. (+)-Terrein was loaded in the holes, and folic acid-chitosan worked as a gatekeeper by disulfide linkage controlling (+)-terrein release in the tumor microenvironment. The (+)-terrein drug delivery systems exhibited cytotoxicity toward A549 cells through induction of apoptosis. The apoptosis effect was confirmed by the increase in the expression of cleaved caspase-3, caspase-9, and PARP. Taken together, this work evaluates for the first time the (+)-terrein delivery system and provides a promising nanomedicine platform for (+)-terrein.

Natural skin-whitening compounds for the treatment of melanogenesis (Review)

Melanogenesis is the process for the production of melanin, which is the primary cause of human skin pigmentation. Skin-whitening agents are commercially available for those who wish to have a lighter skin complexions. To date, although numerous natural compounds have been proposed to alleviate hyperpigmentation, insufficient attention has been focused on potential natural skin-whitening agents and their mechanism of action from the perspective of compound classification. In the present article, the synthetic process of melanogenesis and associated core signaling pathways are summarized. An overview of the list of natural skin-lightening agents, along with their compound classifications, is also presented, where their efficacy based on their respective mechanisms of action on melanogenesis is discussed.

Efficient Production of the Potent Antimicrobial Metabolite “Terrein” From the Fungus Aspergillus terreus

The endophytic fungus Aspergillus terreus (JAS-2) derived from Achyranthes aspera possesses multiple bioactive metabolites, one of which is terrein, a potent antimicrobial substance. Here we report the improved biosynthesis of terrein in cultures grown in media with a fixed carbon and modified nitrogen source (4% dextrose, 1% casein) for 15 days, after which pure crystals of terrein were obtained in the culture medium. We suggest that our improved method is effective for improving the quantity and quality of terrein produced. Terrein has shown potent antimicrobial activities against various microbes that may lead to its further use to combat antimicrobial resistance which threatens the community worldwide.

Large-Scale Production of Bioactive Terrein by Aspergillus terreus Strain S020 Isolated from the Saudi Coast of the Red Sea

The diversity of symbiotic fungi derived from two marine sponges and sediment collected off Obhur, Jeddah (Saudi Arabia), was investigated in the current study. A total of 23 isolates were purified using a culture-dependent approach. Using the morphological properties combined with internal transcribed spacer-rDNA (ITS-rDNA) sequences, 23 fungal strains (in the majority Penicillium and Aspergillus) were identified from these samples. The biological screening (cytotoxic and antimicrobial activities) of small-scale cultures of these fungi yielded several target fungal strains which produced bioactive secondary metabolites. Amongst these isolates, the crude extract of Aspergillus terreus strain S020, which was cultured in fermentation static broth, 21 L, for 40 days at room temperature on potato dextrose broth, displayed strong antimicrobial activities against Pseudomonas aeruginosa and Staphylococcus aureus and significant antiproliferative effects on human carcinoma cells. Chromatographic separation of the crude extract by silica gel column chromatography indicated that the S020 isolate could produce a series of chemical compounds. Among these, pure crystalline terrein was separated with a high yield of 537.26 ± 23.42 g/kg extract, which represents the highest fermentation production of terrein to date. Its chemical structure was elucidated on the basis of high-resolution electrospray ionization mass spectrometry (HRESIMS) or high-resolution mass spectrometry (HRMS), 1D, and 2D NMR spectroscopic analyses and by comparison with reported data. The compound showed strong cytotoxic activity against colorectal carcinoma cells (HCT-116) and hepatocellular carcinoma cells (HepG2), with IC₅₀ values of 12.13 and 22.53 µM, respectively. Our study highlights the potential of A. terreus strain S020 for the industrial production of bioactive terrein on a large scale and the importance of future investigations of these strains to identify the bioactive leads in these fungal extracts.

Terrein is an inhibitor of quorum sensing and c-di-GMP in Pseudomonas aeruginosa: a connection between quorum sensing and c-di-GMP

To address the drug-resistance of bacterial pathogens without imposing a selective survival pressure, virulence and biofilms are highly attractive targets. Here, we show that terrein, which was isolated from Aspergillus terreus, reduced virulence factors (elastase, pyocyanin, and rhamnolipid) and biofilm formation via antagonizing quorum sensing (QS) receptors without affecting Pseudomonas aeruginosa cell growth. Additionally, the effects of terrein on the production of QS signaling molecules and expression of QS-related genes were verified. Interestingly, terrein also reduced intracellular 3,5-cyclic diguanylic acid (c-di-GMP) levels by decreasing the activity of a diguanylate cyclase (DGC). Importantly, the inhibition of c-di-GMP levels by terrein was reversed by exogenous QS ligands, suggesting a regulation of c-di-GMP levels by QS; this regulation was confirmed using P. aeruginosa QS mutants. This is the first report to demonstrate a connection between QS signaling and c-di-GMP metabolism in P. aeruginosa, and terrein was identified as the first dual inhibitor of QS and c-di-GMP signaling.

Terrein reduces age-related inflammation induced by oxidative stress through Nrf2/ERK1/2/HO-1 signalling in aged HDF cells

This study investigated whether multiple bioactivity of terrein such as anti-inflammatory and anti-oxidant inhibits age-related inflammation by promoting an antioxidant response in aged human diploid fibroblast (HDF) cells. HDF cells were cultured serially for in vitro replicative senescence. To create the ageing cell phenotype, intermediate stage (PD31) HDF cells were brought to stress-induced premature senescence (SIPS) using hydrogen peroxide (H2 O2). Terrein increased cell viability even with H2O2 stress and reduced inflammatory molecules such as intracellular adhesion molecule-1 (ICAM-1), cyclooxygenase-2 (COX-2), interleukin-1beta (IL-1β) and tumour necrosis factor-alpha (TNF-α). Terrein reduced also phospho-extracellular kinase receptor1/2 (p-EKR1/2) signalling in aged HDF cells. SIPS cells were attenuated for age-related biological markers including reactive oxygen species (ROS), senescence associated beta-galactosidase (SA β-gal.) and the aforementioned inflammatory molecules. Terrein induced the induction of anti-oxidant molecules, copper/zinc-superoxide defence (Cu/ZnSOD), manganese superoxide dismutase (MnSOD) and heme oxygenase-1 (HO-1) in SIPS cells. Terrein also alleviated reactive oxygen species formation through the Nrf2/HO-1/p-ERK1/2 pathway in aged cells. The results indicate that terrein has an alleviative function of age-related inflammation characterized as an anti-oxidant. Terrein might be a useful nutraceutical compound for anti-ageing.

Modification of artificial sea water for the mass production of (+)-terrein by Aspergillus terreus strain PF26 derived from marine sponge Phakellia fusca

(+)-Terrein shows multiple bioactivities, however, its mass production is a big challenge. Aspergillus terreus strain PF26 derived from South China Sea sponge Phakellia fusca has been cultured to produce (+)-terrein successfully, but artificial sea water (ASW) of high salinity used in the fermentation medium may cause the corrosion risk of metal bioreactor, which limits the fermentation on a large scale. In this study, we modified the components of ASW by removing NaCl and CaCl2 from the original formula, which reduced about 80% salinity of ASW. As a result, 7·56 g l(-1) (+)-terrein production was achieved in shake flask, which was 78·72% higher than using the original ASW, and the cultivation time was decreased from 24 to 15 days. Then, the modified ASW was used for the fermentation of A. terreus strain PF26 in a 500 l stirred bioreactor, consequently 2·5 g l(-1) of (+)-terrein production was achieved.

SIGNIFICANCE AND IMPACT OF THE STUDY

The fermentation of marine micro-organisms always needs to use sea water or artificial sea water (ASW), which limits the fermentation on a large scale, as the high-salinity medium may cause the corrosion risk of bioreactor. In this study, the ASW formula is simplified to reduce the sea water salinity and improve the yield of (+)-terrein, finally, the modified ASW was successfully used for the mass production of (+)-terrein by A. terreus strain PF26 in a 500 l bioreactor.

Synthetic (+)-terrein suppresses interleukin-6/soluble interleukin-6 receptor induced-secretion of vascular endothelial growth factor in human gingival fibroblasts

Interleukin (IL)-6 is a proinflammatory cytokine that performs a wide variety of biological functions, including important roles in the progression of chronic inflammatory diseases such as periodontal disease. (+)-Terrein, a secondary bioactive fungal metabolite isolated from Aspergillus terreus, has various biological activities; however, its anti-inflammatory effects are still unknown. The purpose of this study was to examine the effect of synthetic (+)-terrein on IL-6 signaling and related protein production in human gingival fibroblasts. To our knowledge, this study is the first to report that synthetic (+)-terrein is not cytotoxic at concentrations less than 20 μM and suppresses IL-6/soluble IL-6 receptor (sIL-6R)-induced phosphorylation of signal transducer and activator of transcription-3, extracellular signal-regulated kinase 1/2, and c-jun N-terminal kinase 1/2-signaling proteins that are downstream of IL-6 signaling. In addition, synthetic (+)-terrein suppresses IL-6/sIL-6R-induced vascular endothelial growth factor (VEGF) secretion in a concentration-dependent manner (p<0.01). These data suggest that synthetic (+)-terrein has potential anti-IL-6 signaling activity and suppresses VEGF-associated inflammatory disease progression.

Natural Melanogenesis Inhibitors Acting Through the Down-Regulation of Tyrosinase Activity

Melanogenesis is a biosynthetic pathway for the formation of the pigment melanin in human skin. A key enzyme, tyrosinase, catalyzes the first and only rate-limiting steps in melanogenesis, and the down-regulation of enzyme activity is the most reported method for the inhibition of melanogenesis. Because of the cosmetically important issue of hyperpigmentation, there is a big demand for melanogenesis inhibitors. This encourages researchers to seek potent melanogenesis inhibitors for cosmetic uses. This article reviews melanogenesis inhibitors that have been recently discovered from natural sources. The reaction mechanisms of the inhibitors on tyrosinase activity are also discussed.

Enhancement of osteoblast biocompatibility on titanium surface with Terrein treatment

Titanium is biocompatible with bodily tissues. However, the formation of ROS on the titanium surfaces might have negative response of the activity of the surroundings cells. Terrein was isolated from Penicullium sp. 20135 and found to reduce the effects of LPS-induced inflammation. This study examined the role of Terrein on the biocompatibility of titanium to determine if it can help improve osseointegration. MC-3T3 E1 cells were grown on titanium surfaces. The biocompatibility of Terrein was examined by adding it directly to the culture media at the indicated concentration. The cells on the titanium surface produced excessive ROS and decreased the activity of Cu/Zn SOD and Mn SOD. Moreover, the cells had higher activity towards oxidative stress molecules, such as MAPK, FAK and iNOS expression. In addition, MC-3T3 E1 osteoblast-like cells promoted osteoclast differentiation but reduced osteoblast differentiation and mineralization on the titanium surface. Interestingly, the cells given the Terrein treatment showed higher resistance towards oxidative stress through the up-regulation of ERK1/2 and FAK activity but the down-regulation of SAPK/JNK and iNOS activity. Moreover, Terrein promoted osteoblast differentiation and bone mineralization to elevate the activity of ALP, SPARC and down-regulate RANKL expression after blocking NF-κB translocation from the cytosol to the nucleus. In conclusion, the presence of Terrein on titanium surfaces increases osteoblast cell growth without inflammation. Moreover, Terrein, as a putative antioxidant agent, may enhance osseointegration by decreasing the level of ROS and having a potentially synergistic effect on osteoblast differentiation.

The hypopigmentary action of KI-063 (a new tyrosinase inhibitor) combined with terrein

Resorcinol derivatives are known to inhibit melanin synthesis. In this study, resorcinol derivatives were synthesized and screened for their activity on melanogenesis. KI-063 (a tyrosinase inhibitor) was examined for its effects on melanogenesis using a spontaneously immortalized mouse melanocyte cell line (Mel-Ab). In a cell-free system, KI-063 directly inhibited tyrosinase, the rate-limiting melanogenic enzyme. Moreover, in a cell system, it inhibited melanin synthesis in a concentration-dependent manner. In addition, KI-063 inhibited the activity of cellular tyrosinase. Thus, this study examined the effects of a combination of KI-063 with terrein, an agent that down-regulates microphthalmia-associated transcription factor. The data suggest that KI-063 has an additive effect in combination with terrein. Thus, the suppression of tyrosinase activity by KI-063 and the inhibition of tyrosinase production by terrein appear to be an optimal combination for skin whitening.

Long-term suppression of tyrosinase by terrein via tyrosinase degradation and its decreased expression

Previously, we reported that a fungal metabolite, terrein, decreases melanin synthesis via downregulation of microphthalmia-associated transcription factor (MITF). In the present study, we further investigated the long-term hypopigmenting action of terrein in a spontaneously immortalized mouse melanocyte cell line, Mel-Ab. Treatment with terrein at a concentration of 50 mum strongly decreased melanogenesis in a time-dependent manner. Interestingly, the decreased tyrosinase protein levels lasted for at least 7 days, even though the MITF protein levels were restored after 3 days of treatment. In accordance with the results of Western blot analyses, the tyrosinase mRNA levels were found to be continuously decreased for at least 7 days, even though recovery of the MITF mRNA levels began after 3 days of terrein treatment. Therefore, we evaluated tyrosinase downregulation to determine if it is caused by proteasomal degradation. We found that the reduction in tyrosinase levels that was induced by terrein was clearly recovered by MG-132, a proteasome inhibitor. Moreover, ubiquitination of tyrosinase increased following treatment with terrein in the presence of MG-132. Taken together, these results suggest that terrein decreases melanogenesis through ubiquitin-dependent proteasomal degradation as well as via decreased expression of its mRNA.

Terrein reduces pulpal inflammation in human dental pulp cells

Terrein is a bioactive fungal metabolite whose anti-inflammatory properties are virtually unknown. The purpose of this study was to determine the effects of terrein on lipopolysaccharide (LPS)-induced expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in human dental pulp cells and to determine the mechanism of the observed effects. The LPS-induced expression of ICAM-1 and VCAM-1 was inhibited by terrein in both a time- and dose-dependent manner. LPS-stimulated translocation of nuclear factor kappa B (NF-kappaB) into the nucleus, which was blocked by inhibitors of amino kinase terminal (AKT, LY294002), extracellular signal regulated kinase 1/2 (ERK 1/2, PD98059), p38 (SB203580), and c-jun NH2-terminal kinase (JNK, SP600125) or terrein. In addition, these inhibitors and terrein also reduced the level of ICAM-1 and VCAM-1 expression in LPS-induced inflammation of pulp cells. Terrein suppressed NF-kappaB activation by blocking the activation of Akt. These results strongly suggest the potential role of terrein as an anti-inflammatory modulator in pulpal inflammation.