1,3,5,6-tetrahydroxyxanthone promotes diuresis, renal protection and antiurolithic properties in normotensive and hypertensive rats

Characterization of Diclofenac-induced Renal Damage in Normotensive and Hypertensive Rats: A Comparative Analysis

BACKGROUND

Diclofenac is the non-steroidal anti-inflammatory drug (NSAID) mostly prescribed worldwide, but it is highly associated with hypertension and acute kidney injury. Despite that, little information is available about the renal effects of diclofenac in hypertensive individuals, which led us to carry out this comparative study between the renal effects of this NSAID in normotensive (NTR) and spontaneously hypertensive rats (SHR).

METHODS

Male Wistar NTR and SHR were orally treated with vehicle (V: 10 mL/kg) or diclofenac sodium (D: 100 mg/kg) once a day for 3 days. Urine volume, electrolytes excretion (Na+, K+, Cl-, and Ca2+), urea, creatinine, pH, and osmolarity were evaluated. Furthermore, blood samples and renal tissue were collected to perform biochemical and histological analysis.

RESULTS

Diclofenac increased the renal corpuscle and bowman's space in the SHR, while no microscopic changes were observed in the renal tissue of NTR. Regarding the urinary parameters, diclofenac reduced urine volume, pH, osmolarity, and all electrolytes excretion, followed by decreased urea and creatinine levels in both lineages. Moreover, it also induced hyponatremia, hypokalemia, and hypocalcemia in SHR, while reduced glutathione-S-transferase activity, lipid hydroperoxides, and nitrite levels in renal tissue.

CONCLUSIONS

The data presented herein demonstrated that diclofenac induces renal damage and impaired renal function in both NTR and SHR, but those effects are exacerbated in SHR, as seen by the histological changes and electrolytes balance disturbance, therefore, reinforcing that diclofenac may increase the risks of cardiovascular events in hypertensive patients.

Diuretic, Natriuretic, And Ca2+-Sparing Effect Of The Alkaloid Boldine In Rats

BACKGROUND

Previous studies indicate the renal vasodilating effects of boldine, an alkaloid found in Peumus boldus. However, its potential to induce diuresis still needs to be studied.

METHODS

Wistar rats were used and the urine volume was noted for 8 h and further studied.

RESULTS

The acute treatment at 0.1 and 0.3 mg/kg of boldine showed a diuretic, natriuretic, and Ca2+-sparing effect in rats without changing the urinary elimination of K+and Cl-. When boldine was given in combination with hydrochlorothiazide, there was an increase in urinary volume compared to the vehicle group. However, this was not different from the treatments in its isolated form. Urine Ca2+values ​​remained low but were not enhanced by this association. The excretion of Na+and Cl- was significantly increased compared to the group that received only vehicle or boldine. On the other hand, although the association of amiloride plus boldine did not result in a diuretic effect, the increase in Na+and the reduction in K+excretion were significantly potentiated. Furthermore, in the presence of the non-selective muscarinic receptor antagonist atropine, boldine showed reduced capacity to increase urinary volume, maintaining the natriuretic and Ca2+-sparing effect, besides a very evident K+-sparing action. Similar results were obtained in the presence of the non-selective cyclooxygenase inhibitor indomethacin. Furthermore, boldine showed an ex vivo antiurolithiasis activity, reducing calcium oxalate's precipitation and crystallization.

CONCLUSIONS

This study reveals the diuretic, natriuretic, Ca2+-sparing, and antiurolithiatic effects of boldine, an action possibly related to muscarinic receptor activation and prostanoid generation.

The Chemical and Pharmacological Research Progress on a Kind of Chinese Herbal Medicine, Fructus Malvae

Since the outbreak of the COVID-19 pandemic, traditional Chinese medicine has played an important role in the treatment process. Furthermore, the discovery of artemisinin in Artemisia annua has reduced the incidence of malaria all over the world. Therefore, it is becoming urgent and important to establish a novel method of conducting systematic research on Chinese herbal medicine, improving the medicinal utilization value of traditional Chinese medicine and bringing great benefits to human health all over the world. Fructus Malvae, a kind of Chinese herbal medicine which has been recorded in the “Chinese Pharmacopoeia” (2020 edition), refers to the dry, ripe fruits of Malva verticillata L. Recently, some studies have shown that Fructus Malvae exhibits some special pharmacological activities; for example, it has diuretic, anti-diabetes, antioxidant and anti-tumor properties, and it alleviates hair loss. Furthermore, according to the reports, the active ingredients separated and identified from Fructus Malvae contain some very novel compounds such as nortangeretin-8-O-β-d-glucuronopyranoside and 1-O-(6-deoxy-6-sulfo)-glucopyranosyl-2-O-linolenoyl-3-O-palmitoyl glyceride, which could be screened as important candidate compounds for diabetes- or tumor-treatment drugs, respectively. Therefore, in this research, we take Fructus Malvae as an example and systematically summarize the chemical constituents and pharmacological activity research progress of it. This review will be helpful in promoting the development and application of Fructus Malvae and will also provide an example for other investigations of traditional Chinese medicine.

Xanthone Biosynthetic Pathway in Plants: A Review

Xanthones are secondary metabolites rich in structural diversity and possess a broad array of pharmacological properties, such as antitumor, antidiabetic, and anti-microbes. These aromatic compounds are found in higher plants, such as Clusiaceae, Hypericaceae, and Gentianaceae, yet their biosynthetic pathways have not been comprehensively updated especially within the last decade (up to 2021). In this review, plant xanthone biosynthesis is detailed to illuminate their intricacies and differences between species. The pathway initially involves the shikimate pathway, either through L-phenylalanine-dependent or -independent pathway, that later forms an intermediate benzophenone, 2,3',4,6-tetrahydoxybenzophenone. This is followed by a regioselective intramolecular mediated oxidative coupling to form xanthone ring compounds, 1,3,5-trihydroxyxanthone (1,3,5-THX) or 1,3,7-THX, the core precursors for xanthones in most plants. Recent evidence has shed some lights onto the enzymes and reactions involved in this xanthone pathway. In particular, several biosynthetic enzymes have been characterized at both biochemical and molecular levels from various organisms including Hypericum spp., Centaurium erythraea and Garcinia mangostana. Proposed pathways for a plethora of other downstream xanthone derivatives including swertianolin and gambogic acid (derived from 1,3,5-THX) as well as gentisin, hyperixanthone A, α-mangostin, and mangiferin (derived from 1,3,7-THX) have also been thoroughly covered. This review reports one of the most complete xanthone pathways in plants. In the future, the information collected here will be a valuable resource for a more directed molecular works in xanthone-producing plants as well as in synthetic biology application.

Boldine, an Alkaloid from Peumus boldus Molina, Induces Endothelium-Dependent Vasodilation in the Perfused Rat Kidney: Involvement of Nitric Oxide and Small-Conductance Ca2+-Activated K+ Channel

Boldine, 2,9-dihydroxy-1,10-dimethoxyaporphine, is the main alkaloid found in the leaves and bark of Peumus boldus Molina. In recent years, boldine has demonstrated several pharmacological properties that benefit endothelial function, blood pressure control, and reduce damage in kidney diseases. However, the renal vasodilator effects and mechanisms remain unknown. Herein, perfused rat kidneys were used to study the ability of boldine to induce vasodilation of renal arteries. For that, left kidney preparations with and without functional endothelium were contracted with phenylephrine and received 10–300 nmol boldine injections. The preparations were then perfused for 15 min with phenylephrine plus L-NAME, indomethacin, KCl, tetraethylammonium, glibenclamide, apamin, charybdotoxin, or iberiotoxin. In 30, 100, and 300 nmol doses, boldine induced a dose-and endothelium-dependent relaxing effect on the renal vascular bed. No vasodilator effects were observed in preparations lacking functional endothelium. While the inhibition of the cyclooxygenase enzyme through the addition of indomethacin did not cause any change in the vasodilating action of boldine, the nonselective nitric oxide synthase inhibitor L-NAME fully precluded the vasodilatory action of boldine at all doses tested. The perfusion with KCl or tetraethylammonium (nonselective K⁺ channels blocker) also abolished the vasodilatory effect of boldine, indicating the participation of K⁺ channels in the renal action of boldine. The perfusion with glibenclamide (selective ATP-sensitive K⁺ channels blocker), iberiotoxin (selective high-conductance Ca²⁺-activated K⁺ channel blocker), and charybdotoxin (selective high- and intermediate-conductance Ca²⁺-activated K⁺ channel blocker) did not modify the vasodilatory action of boldine. On the other hand, the perfusion with apamin (selective small-conductance Ca²⁺-activated K⁺ channel blocker) completely prevented the vasodilatory action of boldine at all doses tested. Together, the present study showed the renal vasodilatory properties of boldine, an effect dependent on the generation of nitric oxide and the opening of a small-conductance Ca²⁺-activated K⁺ channel.