Immunosuppressive constituents from Urtica dentata Hand

Ethnomedicinal Uses, Geographical Distribution, Botanical Description, Phytochemistry, Pharmacology, and Quality Control of Laportea bulbifera (Sieb. et Zucc.) Wedd.: A Review

Laportea bulbifera (Sieb. et Zucc.) Wedd. (L. bulbifera) is a significant plant in the Laportea genus. Traditionally, it has been used in ethnomedicine for treating various conditions such as rheumatic arthralgia, fractures, falling injuries, nephritis dropsy, limb numbness, pruritus, fatigue-induced internal imbalances, and irregular menstruation. Modern pharmacological studies have confirmed its therapeutic potential, including anti-inflammatory, immunosuppressive, analgesic, and anti-rheumatoid arthritis properties. To gather comprehensive information on L. bulbifera, a thorough literature search was conducted using databases like Web of Science, PubMed, ProQuest, and CNKI. This review aims to provide a comprehensive understanding of L. bulbifera, covering various aspects such as ethnomedicinal uses, geographical distribution, botanical description, phytochemistry, pharmacology, and quality control. The goal is to establish a solid foundation and propose new research avenues for exploring and developing potential applications of L. bulbifera. So far, a total of one hundred and eighty-nine compounds have been isolated and identified from L. bulbifera, including flavonoids, phenolics, nitrogen compounds, steroids, terpenoids, coumarins, phenylpropanoids, fatty acids and their derivatives, and other compounds. Notably, flavonoids and fatty acids have demonstrated remarkable antioxidant and anti-inflammatory properties. Additionally, these compounds show promising potential in activities such as analgesia, hypoglycemia, and hypolipidemia, as well as toxicity. Despite extensive fundamental studies on L. bulbifera, further research is still needed to enhance our understanding of its mechanism of action and improve quality control. This requires more comprehensive investigations to explore the specific material basis, uncover new mechanisms of action, and refine quality control methods related to L. bulbifera. By doing so, we could contribute to the further development and utilization of this plant.

Identification of Laportea bulbifera using the complete chloroplast genome as a potentially effective super-barcode

Laportea bulbifera, a Miao medicine grown in karst areas, has exerted a unique curative effect on skin itching in the elderly, with an annual sales of > 100 million Yuan. Owing to the shortage of resources and large morphological variations in L. bulbifera, it is difficult to identify the species correctly using only traditional methods, which seriously affects the safety of drug usage for patients. This study obtained the complete high-quality L. bulbifera chloroplast (cp) genome, using second- and third-generation high-throughput sequencing. The cp genome was 149,911 bp in length, with a typical quadripartite structure. A total of 127 genes were annotated, including 83 protein-coding genes, 36 tRNA genes, and 8 rRNA genes. There was an inverted small single copy (SSC) structure in the L. bulbifera cp genome, one large-scale rearrangement of ~ 39 kb excised in the SSC and IR regions. The complete cp genome sequence is used as a potentially effective super-barcode and the highly variable regions (ycf1, matK, and ndhD) can be used as potentially specific barcodes to accurately distinguish L. bulbifera from counterfeits and closely related species. This study is important for the identification of L. bulbifera and lays a theoretical foundation for elucidating the phylogenetic relationship of the species.

The complete chloroplast genome of Laportea bulbifera (Sieb. et Zucc.) Wedd. and its phylogenetic analysis

The circle complete chloroplast genome of Laportea bulbifera (Sieb. et Zucc.) Wedd. was sequenced for the first time. The genome length of L. bulbifera is 150,042 bp with 36.80% of GC content. The genome consists of a large single copy (LSC) region of 82,414 bp, a small single copy (SSC) region of 17,714 bp, and two inverted repeat (IRa and IRb) regions of 24,957 bp each. A total of 129 genes were annotated, including 84 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. Phylogenetic analysis was conducted by 29 species from the Rosales, the results presented a closed relationship between the species Laportea bulbifera and Poikilospermum lanceolatum.

Rare biscoumarin derivatives and flavonoids from Hypericum riparium

Hypericum riparium A. Chev. is a Cameroonian medicinal plant belonging to the family Guttiferae. Chemical investigation of the methanol extract of the stem bark of H. riparium led to the isolation of four natural products, 7,7'-dihydroxy-6,6'-biscoumarin (1), 7,7'-dihydroxy-8,8'-biscoumarin (2), 7-methoxy-6,7'-dicoumarinyl ether (3), 2'-hydroxy-5'-(7″-methoxycoumarin-6″-yl)-4'-methoxyphenylpropanoic acid (4), together with one known 7,7'-dimethoxy-6,6'-biscoumarin (5), two flavones, 2'-methoxyflavone (6) and 3'-methoxy flavone (7), and two steroids, stigmast-4-en-3-one (8) and ergosta-4,6,8,22-tetraen-3-one (9). In addition, tetradecanoic acid (10), n-pentadecanoic acid (11), hexadecanoic acid (12), cis-10-heptadecenoic acid (13), octadecanoic acid (14) campesterol (15), stigmasterol (16), β-sitosterol (17), stigmastanol (18), β-eudesmol (19), 1-hexadecanol (20), and 1-octadecanol (21) were identified by GC-MS analysis. Compound 4 consists of a phenylpropanoic acid derivative fused with a coumarin unit, while compounds 2 and 3 are rare members of C8-C8' and C7-O-C6 linked biscoumarins. Their structures were elucidated by UV, IR, extensive 1D- and 2D-NMR experiments and electrospray (ESI) high resolution mass spectrometry (MS) including detailed MS/MS studies. This is the first report on the isolation of biscoumarins from the genus Hypericum, although simple coumarin derivatives have been reported from this genus in the literature. The cytotoxic activities of compounds 2-5 were evaluated against the human prostate cancer cell line PC-3 and the colon cancer cell line HT-29. They do not exhibit any significant cytotoxic activity.

Identification and quantification of total coumarins from Urtica dentata Hand and its roles in promoting immune tolerance via TLR4-mediated dendritic cell immaturation

Urtica dentata Hand (UDH) is traditionally used in the Alpine region as a herbal medicine. Immunotherapy using total coumarins (TC) of UDH has been proposed, yet the cellular and molecular mechanisms remain incompletely characterized. Additionally, there is no method available for the quantification of the main coumarins in UDH. We describe maturation-resistant, TC-conditioned dendritic cell (DC), which expressed much lower MHC class II (I-Ak) and CD86, showed reduced capacity to stimulate effector T cell responses and upregulated PD-Ll (programmed death ligand-1). TC-DC-stimulated regulatory cells (Treg) were superior alloantigen-specific suppressor of the T effector response as compared to those stimulated by control (CTR)-DC. Furthermore, TC-conditioned DC increased the levels of Foxp3 and CTLA-4 in the CD25 T cell population. TC-DC downregulated toll like receptor 4 (TLR4) protein expression in response to LPS. This indicates that down-regulation of TLR4 in response to TC on DC is a critical signaling pathway that regulates the phenotype and function of DC. We also established a sensitive and specific high-performance liquid chromatography-diodearray detection-mass spectrometry (HPLC-DAD-MS) method for simultaneous identification of its main coumarins, 6,6',7,7'-tetramethoxyl-8,8'-biscoumarin (1), 7,7'-dihydroxy-6,6'-dimethoxy-8,8'-biscoumarin (2), 7,7'-dimethoxy-6,6'-biscoumarin (3), and scoparone (4). A demonstration of this mechanism and the method for identification and quantification of TC in UDH endorsed their potential as a tolerance-promoting herbal medicine to prevent or treat transplantation rejection and autoimmune diseases.

Total coumarins from Urtica dentata Hand prevent murine autoimmune diabetes via suppression of the TLR4-signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Urtica dentata Hand (UDH), the root of Laportea bulbifera (Sieb. et. Zucc.) Wedd, has been traditionally used in traditional Chinese medicine as an anti-inflammatory and immuno-regulatory agent for rheumatoid arthritis and some other autoimmune diseases treatment. And the coumarins are the major components of UDH.

AIM OF THE STUDY

To investigate the effect of total coumarins (TC) isolated from UDH on the development of autoimmune diabetes.

MATERIALS AND METHODS

Eight-week-old non-obese diabetic (NOD) mice were randomly divided into four groups: control group, low-dose (37.5 mg/kg), middle-dose (75 mg/kg), and high-dose (150 mg/kg) TC-treatment groups. NOD mice were then given with a suspension of TC or saline by intragastric (i.g.) administration every other day. After 4 weeks of treatment, 8 mice at 12-weeks of age per group were randomly selected to be sacrificed to perform intraperitoneal glucose tolerance test, examine histopathological insulitis, spleen T lymphocyte proliferation, the percentage of CD4+CD25+Foxp3+ T regulatory cell (Treg), dendritic cell (DC) surface molecules, toll-like receptor (TLR)4 expression and signal pathways involved. The remaining 10 mice per group were kept until 26 weeks of age to assess the incidence of diabetes. We also studied the direct effect of TC on DC and CD4+CD25+ Tregs in vitro.

RESULTS

Treatment with TC for 4 weeks significantly inhibited insulitis, increased pancreatic islet number, delayed the onset and decreased the development of diabetes by 26 weeks of age in NOD mice, compared with the untreated control mice. TC suppressed spleen T lymphocyte proliferation, induced Th2-biased cytokine response, the generation of CD4+CD25+Foxp3+ Tregs and Foxp3 mRNA expression. And TC-treated DCs were characterized as low expression of MHC class II and CD86 molecules. TLR4 gene and protein expressions in the spleen, thymus and pancreas were down-regulated in TC-treated groups. The key molecules in the downstream signaling cascades of TLR4, including myeloid differentiation factor (MyD)88, nuclear factor (NF)-κB, IL-1β, Toll-IL-1 receptor domain-containing adaptor inducing interferon-β(TRIF), TRIF-related adaptor molecule (TRAM), interferon regulatory factor (IRF)-3 and IFN-β, all decreased significantly in TC groups, suggesting that TC inhibits both MyD88-dependent and -independent pathways of TLR4. At the cellular level, however, TLR4 protein expression in DCs, but not in Tregs, was downregulated by TC. And TC strengthened the role of DC, not Treg, in negative immune regulation in vitro. In contrast, anti-TLR4 antibody could block the effect of TC on DCs immune function.

CONCLUSION

These results suggest that TC extracted from UDH prevent the development of autoimmune diabetes in NOD mice via suppression of the TLR4-signaling pathways. TC maintain the DCs in an immature tolerogenic state, at least in part, mediated by down-regulating TLR4-signaling pathways in DCs, then enhance Treg differentiation, shift toward Th2 and suppress T lymphocyte proliferation.

Therapeutic effects of total coumarins from Urtica dentata Hand on collagen-induced arthritis in Balb/c mice

ETHNOPHARMACOLOGICAL RELEVANCE

Urtica dentata Hand (UDH), the root of Laportea bulbifera (Sieb. et. Zucc.) Wedd, has long been utilized in traditional Chinese medicine for the treatment of rheumatoid arthritis and some other autoimmune diseases. Coumarins are the main active principles contributing to UDH's efficacy, but the mechanisms have not been fully clarified.

AIM OF STUDY

To explore effects of total coumarins (TC) isolated from UDH on the development of type II collagen (CII)-induced arthritis (CIA) in Balb/c mice.

MATERIALS AND METHODS

Arthritis was induced in Balb/c mice by immunization with an emulsion of 200mg CII and complete Freund's adjuvant (CFA). The CIA mice were then given with a suspension of TC or saline by intragastric (i.g.) administration every other day. The incidence and severity of disease and histopathology of inflammation were assessed. Inflammatory response was determined by measuring the levels of different inflammation mediators in serum. The effect of TC on differentiation of CD4(+)CD25(+) Foxp3(+)Treg cells was examined by flow cytometry. The phenotype of bone marrow-derived dendritic cells (DCs), T-bet mRNA level and IL-12p70 secretion by DCs were also detected.

RESULTS

Pharmacologically, treatment with TC for type II collagen induced arthritis in mice through oral administration displayed significant and dose-dependent drop of clinical arthritis score and paw swelling, compared with the untreated CIA mice. Pathologic changes showed that TC protected tissues against bone destruction, whereas an almost complete destruction occurred in the CIA model group. The protective status was associated with a substantial decrease in the production of IFN-γ and IL-2, an increase of IL-10 and TGF-β and suppressive expression of T-bet in DCs. TC also induced the generation of CD4(+)CD25(+) Treg cells with a Treg phenotype Foxp3. TC-treated DCs were characterized as low expression of MHC class II and CD86 molecules, as well as a reduction of IL-12p70.

CONCLUSIONS

Our data suggest that TC provides substantial therapeutic protection against CIA by eliciting immune tolerance and it would be a valuable candidate for further investigation as a new anti-arthritic agent.