Khellin

J Enzyme Inhib Med Chem. 2013 Dec;28(6):1171-81.

Molecular modeling study bioactive natural product of khellin analogues as a novel potential pharmacophore of EGFR inhibitors.[Pubmed: 23025406]

Khelline is naturally occurring furochromone exhibited significant Epidermal Growth Factor Receptor (EGFR) inhibitory activity. The newly synthesized compounds 2-5 displayed the most potent EGFR inhibitory activity on MCF-7 and HeLa.
METHODS AND RESULTS:
In vitro study against 59 different human tumour cell lines derived from nine cancer type in NCI (USA), which was presented and documented. Molecular docking simulation was performed to position compounds 1-5 into the EGFR active site to determine the probable binding mode.

PLoS One. 2013 Sep 19;8(9):e74917.

Khellin and visnagin differentially modulate AHR signaling and downstream CYP1A activity in human liver cells.[Pubmed: 24069365]

Khellin and visnagin are two furanochromones that can be frequently found in ethnomedical formulations in Asia and the Middle East. Both compounds possess anti-inflammatory and analgesic properties, therefore modern medicine uses these compounds or structurally related derivatives for treatment of vitiligo, bronchial asthma and renal colics. Despite their frequent usage, the potential toxic properties of visnagin and Khellin are not well characterized up-to-now. Many natural compounds modulate the expression and activity of cytochrome P450 1A1 (CYP1A1), which is well-known to bioactivate pro-carcinogens. The expression of this enzyme is controlled by the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor and regulator of drug metabolism.
METHODS AND RESULTS:
Here, we investigated the influence of both furanochromones on AHR signaling in human HepG2 hepatocarcinoma cells and primary human hepatocytes. Both compounds transactivated xenobiotic response element (XRE)-driven reporter gene activity in a dose-dependent manner and induced CYP1A1 transcription in HepG2 cells and primary hepatocytes. The latter was abolished in presence of a specific AHR antagonist. CYP1A enzyme activity assays done in HepG2 cells and primary hepatocytes revealed an inhibition of enzyme activity by both furanochromones, which may become relevant regarding the metabolism of xenobiotics and co-administered therapeutic drugs.
CONCLUSIONS:
The observed induction of several other members of the AHR gene battery, whose gene products are involved in regulation of cell growth, differentiation and migration, indicates that a further toxicological characterization of visnagin and khelllin is urgently required in order to minimize potential drug-drug interactions and other toxic side-effects that may occur during therapeutic usage of these furanochromones.

J Eur Acad Dermatol Venereol. 2011 Jan;25(1):74-81.

Treatment of vitiligo with khellin liposomes, ultraviolet light and blister roof transplantation.[Pubmed: 20477914 ]

Various surgical and non-surgical methods are available to treat vitiligo. Surgical techniques such as epidermal blister graft transplantation may be effective for the re-pigmentation of stable, but refractory vitiligo areas. Khellin has phototherapeutic properties that are similar to those of the psoralens, but with substantially lower phototoxic effects and DNA mutation effects. Its penetration into the hair follicles is enhanced by encapsulating it into liposomes. Subsequent activation of the Khellin with UV light stimulates the melanocytes in the hair follicles. The first objective was to evaluate the additional value of combining blister roof transplantation (BRT) with Khellin in liposomes and ultraviolet light (KLUV) in the treatment of recalcitrant vitiligo patches. The second objective was to assess patients' satisfaction.
METHODS AND RESULTS:
Nineteen patients with vitiligo lesions which did not respond to KLUV treatment for at least a year were treated with BRT followed by KLUV. The transplantation was performed by creating blisters with a suction device, preparing the target site with Erbium laser ablation and the actual transplantation. Locations where randomly assigned. A blinded observer established the results.
CONCLUSIONS:
Seventy-five percent of the patients were satisfied with the cosmetic result. All of the patients would recommend the treatment to other vitiligo patients. More than 75% re-pigmentation of the vitiligo areas was noted in 47% of the patients according to the blinded evaluation of photographs taken before and after the treatment.

J Am Acad Dermatol. 1988 Apr;18(4 Pt 1):693-701.

Treatment of vitiligo with khellin and ultraviolet A.[Pubmed: 3270995]

Twenty-eight patients with vitiligo were treated with a new photochemotherapeutic regimen using Khellin, a furanochromone, as photosensitizer, together with ultraviolet A (UVA) irradiation.
METHODS AND RESULTS:
Twenty-five patients received Khellin orally and three patients were treated with topical Khellin. Treatments were given three times weekly. As opposed to psoralens, Khellin did not induce skin phototoxicity with UVA but it induced repigmentation similar to psoralens. The treatment success strongly depended on the number of treatments. More than 70% repigmentation was achieved in 41% of the patients who had received 100 to 200 treatments. This success rate is comparable to the rate obtained with psoralens. Seven patients experienced a mild elevation of liver transaminases within the early treatment phase and their treatments were discontinued. No long-term internal organ or skin toxicity was observed. The major advantage of Khellin is that it does not lead to phototoxic skin erythema and thus can be considered safe for home treatment.
CONCLUSIONS:
Because of its photochemistry it may be considered less hazardous than psoralens regarding mutagenicity and carcinogenicity.

Phytomedicine. 2010 Jul;17(8-9):653-8.

An aqueous extract of Ammi visnaga fruits and its constituents khellin and visnagin prevent cell damage caused by oxalate in renal epithelial cells.[Pubmed: 20036111 ]

Teas prepared from the fruits of Ammi visnaga L. (syn. "Khella") have been traditionally used in Egypt as a remedy to treat kidney stones. It was the aim of our study to evaluate the effect of a Khella extract (KE) as well as the two major constituents Khellin and visnagin on renal epithelial injury using LLC-PK1 and Madin-Darby-canine kidney (MDCK) cells. Both cell lines provide suitable model systems to study cellular processes that are possibly involved in the development of a renal stone.
METHODS AND RESULTS:
LLC-PK1 and MDCK cell lines were exposed to 300 microM oxalate (Ox) or 133 microg/cm(2) calcium oxalate monohydrate (COM) in presence or absence of 10, 50, 100 or 200 microg/mL KE. To evaluate cell damage, cell viability was assessed by determining the release of lactate dehydrogenase (LDH). KE (e.g. 100 microg/ml) significantly decreased LDH release from LLC-PK1 (Ox: 8.46+0.76%; Ox + 100 microg/ml KE: 5.41+0.94%, p<0.001) as well as MDCK cells (Ox: 30.9+6.58%; Ox+100 microg/ml KE: 17.5+2.50%, p<0.001), which indicated a prevention of cell damage. Similar effects for KE were observed in both cell lines when COM crystals were added. In LLC-PK1 cells Khellin and visnagin both decreased the % LDH release significantly in cells that were pretreated with Ox or COM crystals. However, Khellin and visnagin exhibited different responses in MDCK cells. Whereas Khellin slightly reduced the % LDH release after exposure of the cells to Ox and COM crystals, visnagin significantly decreased % LDH release only after COM crystal exposure. Overall both compounds were more active in LLC-PK1 than in MDCK cells. In summary, exposure of renal epithelial cells to Ox or COM crystals was associated with a significant release of LDH indicating cell injury.
CONCLUSIONS:
Our data demonstrate that KE as well as Khellin and visnagin could prevent renal epithelial cell damage caused by Ox and COM and could therefore play a potential role in the prevention of stone formation associated with hyperoxaluria.

Br J Dermatol. 2003 Oct;149(4):707-17.

KUVA (khellin plus ultraviolet A) stimulates proliferation and melanogenesis in normal human melanocytes and melanoma cells in vitro.[Pubmed: 14616361]

Khellin is a naturally occurring furochromone which, when combined with artificial ultraviolet (UV) A or solar irradiation (KUVA), is reported to repigment vitiligo skin as effectively as PUVA photochemotherapy. The exact mechanism of KUVA-induced repigmentation is unknown. The aim of this study was to test the effect of Khellin and KUVA on proliferation and melanogenesis of normal human melanocytes and Mel-1 melanoma cells in vitro.
METHODS AND RESULTS:
Cultured normal human melanocytes, Mel-1 melanoma cells and fibroblasts were treated with Khellin, UVA and KUVA and the effect on proliferation determined by cell counting. The effect on melanogenesis was determined by a radiometric melanin formation assay. Changes in gene expression and protein synthesis were determined by Northern blot, reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analyses. Khellin stimulated proliferation of Mel-1 melanoma cells and melanocytes at concentrations between 1 nmol L-1 and 0.5 mmol L-1 with a peak effect at 0.01 mmol L-1 Khellin. In contrast, Khellin inhibited proliferation of fibroblasts over the entire concentration range tested. At concentrations above 0.5 mmol L-1, Khellin was cytotoxic to both melanocytic cells and fibroblasts. Exposure of Khellin-treated cells to single doses of UVA between 150 and 280 mJ cm-2 resulted in an enhanced proliferative effect. Khellin and KUVA also stimulated the melanogenic enzyme activity of pigmented cells, with the most effective treatment being 0.01 mmol L-1 Khellin with 250 mJ cm-2 UVA. Western blot, Northern blot and RT-PCR analysis revealed that these increases in melanogenic enzyme activity were not due to increases in gene expression or protein synthesis. UVA treatment resulted in an increase in enzyme glycosylation and this correlated with the increase in melanogenesis.
CONCLUSIONS:
We conclude that Khellin activated by UVA stimulates melanocyte proliferation and melanogenesis. Our results point to the possibility that current treatment regimens might be improved if reduced Khellin doses are applied and suggest that improved delivery vehicles be tested.

Urol Res. 2011 Jun;39(3):189-95.

Prevention of renal crystal deposition by an extract of Ammi visnaga L. and its constituents khellin and visnagin in hyperoxaluric rats.[Pubmed: 21069311]

In Egypt, teas prepared from the fruits of Ammi visnaga L. (syn. "Khella") are traditionally used by patients with urolithiasis. The aim of this study was to evaluate whether oral administration of an aqueous extract prepared from the fruits of A. visnaga as well as two major constituents Khellin and visnagin could prevent crystal deposition in stone-forming rats.
METHODS AND RESULTS:
Hyperoxaluria was induced in male Sprague-Dawley rats by giving 0.75% ethylene glycol and 1% ammonium chloride via the drinking water. The Khella extract (KE; 125, 250 or 500 mg/kg) was orally administered for 14 days. The histopathological examination of the kidneys revealed that KE significantly reduced the incidence of calcium oxalate (CaOx) crystal deposition. In addition, KE significantly increased urinary excretion of citrate along with a decrease of oxalate excretion. Comparable to the extract, Khellin and visnagin significantly reduced the incidence of CaOx deposition in the kidneys. However, both compounds did not affect urinary citrate or oxalate excretion indicating a mechanism of action that differs from that of the extract. For KE, a reasonably good correlation was observed between the incidence of crystal deposition, the increase in citrate excretion and urine pH suggesting a mechanisms that may interfere with citrate reabsorption.
CONCLUSIONS:
In conclusion, our data suggest that KE and its compounds, Khellin and visnagin, may be beneficial in the management of kidney stone disease caused by hyperoxaluria but that it is likely that different mechanism of action are involved in mediating these effects.