Therapeutic effect of gossypetin against paraquat-induced testicular damage in male rats: a histological and biochemical study

Paraquat (PQ) is an organic compound, which is commonly used as a herbicide in the agriculture sector, and it is also known to stimulate critical damages in the male reproductive system. Gossypetin (GPTN) is one of important members of the flavonoid family, which is an essential compound in flowers and calyx of Hibiscus sabdariffa with potential pharmacological properties. The current investigation was aimed to examine the ameliorative potential of GPTN against PQ-instigated testicular damages. Adult male Sprague-Dawley rats (n = 48) were distributed into four groups: control, PQ (5 mg/kg), PQ + GPTN (5 mg/kg + 30 mg/kg respectively), and GPTN (30 mg/kg). After 56 days of treatment, biochemical, spermatogenic indices, hormonal, steroidogenic, pro-or-anti-apoptotic, and histopathological parameters were estimated. PQ exposure disturbed the biochemical profile by reducing the activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GSR), while it increased the concentration of reactive oxygen species (ROS) and malondialdehyde (MDA) level. Furthermore, PQ exposure decreased the sperm motility, viability, number of hypo-osmotic tail swelled spermatozoa, and epididymal sperm count; additionally, it increased sperm morphological (head mid-piece and tail) abnormalities. Moreover, PQ lessened the follicle-stimulating hormone (FSH), luteinizing hormone (LH), and plasma testosterone levels. Besides, PQ-intoxication downregulated the gene expression of steroidogenic enzymes (StAR, 3β-HSD, and 17β-HSD) and anti-apoptotic marker (Bcl-2), whereas upregulated the gene expression of apoptotic markers (Bax and Caspase-3). PQ exposure led to histopathological damages in testicular tissues as well. Nonetheless, GPTN inverted all the illustrated impairments in testes. Taken together, GPTN could potently ameliorate PQ-induced reproductive dysfunctions due to its antioxidant, androgenic, and anti-apoptotic potential.

Gossypetin ameliorates 5xFAD spatial learning and memory through enhanced phagocytosis against Aβ

BACKGROUND

Microglia are the resident immune cells found in our brain. They have a critical role in brain maintenance. Microglia constantly scavenge various waste materials in the brain including damaged or apoptotic neurons and Aβ. Through phagocytosis of Aβ, microglia prevent the accumulation of Aβ plaque in the brain. However, in Alzheimer's disease (AD) patients, chronic exposure to Aβ makes microglia to become exhausted, which reduces their phagocytic activity against Aβ. Since microglia play an important role in Aβ clearance, enhancing microglial phagocytic activity against Aβ is a promising target for AD treatment. Therefore, there is a great need for therapeutic candidate that enhances microglial Aβ clearance while inhibiting microglia's pathogenic properties.

METHODS

In vivo studies were conducted with 5xFAD AD model mice by treating gossypetin for 13 weeks through intragastric administration. Their spatial learning and memory were evaluated through behavior tests such as Y-maze and Morris Water Maze test. Hippocampus and cortex were acquired from the sacrificed mice, and they were used for histological and biochemical analysis. Also, mouse tissues were dissociated into single cells for single-cell RNA sequencing (scRNA-seq) analysis. Transcriptome of microglial population was analyzed. Mouse primary microglia and BV2 mouse microglial cell line were cultured and treated with fluorescent recombinant Aβ to evaluate whether their phagocytic activity is affected by gossypetin.

RESULTS

Gossypetin treatment improved the spatial learning and memory of 5xFAD by decreasing Aβ deposition in the hippocampus and cortex of 5xFAD. Gossypetin induced transcriptomic modulations in various microglial subpopulations, including disease-associated microglia. Gossypetin enhanced phagocytic activity of microglia while decreasing their gliosis. Gossypetin also increased MHC II⁺ microglial population.

CONCLUSIONS

Gossypetin showed protective effects against AD by enhancing microglial Aβ phagocytosis. Gossypetin appears to be a novel promising therapeutic candidate against AD.

Gossypetin- based therapeutics for cognitive dysfunction in chronic unpredictable stress- exposed mice

Chronic unpredictable stress (CUS) is a promising model for induction of cognition impairment. Stress induced memory dysfunction is linked to the activation of kynurenine (KYN) pathway. This pathway indicates that, chronic stress primarily promotes the release of excessive cortisol from the adrenal gland, which tends to activate microglia and further increases kynurenine and its downstream pathway, resulting in excessive quinolinic acid (QA), which further impairs brain derived neurotrophic factor (BDNF) levels and leads to neurodegeneration. Prior studies already established anti-oxidant and anti-depressant activity of gossypetin. This research study was mainly conducted to elaborate neuroprotective activity of gossypetin against CUS-induced cognition impairment via acting on kynurenine pathway. In this study, Swiss albino mice were exposed to various stressors for five weeks and then administered with gossypetin (5, 10 and 20 mg/kg, i.p.) from the 4^th to the 7^th week (from day 22 to 49). Several behavioral tests were carried out between days 36 to 49 (6^th and 7^th week) and further corticosterone, neurotransmitters, oxidative stress, and brain-derived neurotrophic factor (BDNF) levels were measured. Results state that CUS exposed mice showed significant improvement in the behavioral pattern after gossypetin treatment. Corticosterone levels and oxidative stress was also found to be significantly decreased in gossypetin (10 and 20 mg/kg, i.p.) treated mice when compared with CUS exposed mice. Whereas, serotonin, norepinephrine and BDNF levels were also found to be increased after gossypetin treatment. Hence, gossypetin can be considered as a neuroprotective agent against cognition impairment caused by chronic unpredictable stress.

Identification of a Flavin Monooxygenase-Like Flavonoid 8-Hydroxylase with Gossypetin Synthase Activity from Lotus japonicus

Lotus japonicus is a model legume that accumulates 8-hydroxyflavonol derivatives, such as gossypetin (8-hydroxyquercetin) 3-O-glycoside, which confer the yellow color to its petals. An enzyme, flavonoid 8-hydroxylase (F8H; LjF8H), is assumed to be involved in the biosynthesis, but the specific gene is yet to be identified. The LjF8H cDNA was isolated as a flavin adenine dinucleotide (FAD)-binding monooxygenase-like protein using flower buds and flower-specific EST data of L. japonicus. LjF8H is a single copy gene on chromosome III consisting of six exons. The conserved FAD- and NAD(P)H-dependent oxidase motifs were found in LjF8H. Phylogenetic analysis suggested that LjF8H is a member of the flavin monooxygenase group but distinctly different from other known flavonoid oxygenases. Analysis of recombinant yeast microsome expressing LjF8H revealed that the enzyme catalyzed the 8-hydroxylation of quercetin. Other flavonoids, such as naringenin, eriodictyol, apigenin, luteolin, taxifolin and kaempferol, also acted as substrates of LjF8H. This broad substrate acceptance was unlike known F8Hs in other plants. Interestingly, flavanone and flavanonol, which have saturated C-C bond at positions 2 and 3 of the flavonoid C-ring, produced 6-hyroxylflavonoids as a by-product of the enzymatic reaction. Furthermore, LjF8H only accepted the 2S-isomer of naringenin, suggesting that the conformational state of the substrates might affect product specificity. The overexpression of LjF8H in Arabidopsis thaliana and Petunia hybrida synthesized gossypetin and 8-hydroxykaempferol, respectively, indicating that LjF8H was functional in plant cells. In conclusion, this study represents the first instance of cloning and identification of F8Hs responsible for gossypetin biosynthesis.

Gossypetin Inhibits Solar-UV Induced Cutaneous Basal Cell Carcinoma Through Direct Inhibiting PBK/TOPK Protein Kinase

BACKGROUND

Skin photoaging, skin inflammation and skin cancer are related with excessive exposure to solar UV. PDZ-binding kinase/T-LAK cell-originated protein kinase (PBK/TOPK), a member of the serine/threonine protein kinase, which regulates the signaling cascades of p38 mitogen-activated protein kinase (p38 MAPK) and extracellular signal regulated kinase 1/2 (ERK1/2). PBK/TOPK plays a significant role in solar-UV-induced cutaneous basal cell carcinoma (BCC), and targeting PBK/TOPK can be supposed to treat and prevent cutaneous BCC.

METHODS

The pathological feature and the expression level of PBK/TOPK in cutaneous BCC tissues of human were studied in clinical samples. SUV-induced the phosphorylation of p38 MAPK and ERK1/2 were demonstrated ex vivo. Moreover, the interaction between Gossypetin and PBK/TOPK were detected by in vitro kinase assay and Microscale thermophoresis (MST) assay. Furthermore, the effect of Gossypetin to solar UV-induced the activity of PBK/TOPK were detected ex vivo and in vivo.

RESULTS

The clinical samples showed that the expression levels of PBK/TOPK, phosphor-p38 MAPK and phosphor- ERK1/2 were up-regulated in cutaneous BCC tissues of human. The expression of phosphor-p38 MAPK or phosphor-ERK1/2 increased in a dose and time dependent manner after solar UV treatment in HaCaT cells. MTT cytotoxicity assay results showed that Gossypetin has no effect on HaCaT cells. In vitro kinase assay and MST assay results showed that Gossypetin bound with PBK/TOPK and suppressed PBK/TOPK activity. Ex vivo results showed Gossypetin inhibited solar UV-induced phosphorylation of PBK/TOPK, p38 MAPK, ERK1/2 and H2AX by suppressing PBK/TOPK activity. In vivo test results indicated that Gossypetin suppressed solar UV-induced increase of PBK/TOPK, phosphor-p38 MAPK, phosphor-ERK1/2 and phosphor- H2AX in SKH-1 hairless mice.

CONCLUSION

Our data demonstrated that Gossypetin can alleviate solar-UV-induced cutaneous BCC by blocking PBK/TOPK, and Gossypetin could be a remarkable agent for treating solar-UV induced cutaneous basal cell carcinoma.

Gossypetin is a novel MKK3 and MKK6 inhibitor that suppresses esophageal cancer growth in vitro and in vivo

Gossypetin as a hexahydroxylated flavonoid found in many flowers and Hibiscus. It exerts various pharmacological activities, including antioxidant, antibacterial and anticancer activities. However, the anticancer capacity of gossypetin has not been fully elucidated. In this study, gossypetin was found to inhibit anchorage-dependent and -independent growth of esophageal cancer cells. To identify the molecular target(s) of gossypetin, various signaling protein kinases were screened and results indicate that gossypetin strongly attenuates the MKK3/6-p38 signaling pathway by directly inhibiting MKK3 and MKK6 protein kinase activity in vitro. Mechanistic investigations showed that arginine-61 in MKK6 is critical for binding with gossypetin. Additionally, the inhibition of cell growth by gossypetin is dependent on the expression of MKK3 and MKK6. Gossypetin caused G2 phase cell cycle arrest and induced intrinsic apoptosis by activating caspases 3 and 7 and increasing the expression of BAX and cytochrome c. Notably, gossypetin suppressed patient-derived esophageal xenograft tumor growth in an in vivo mouse model. Our findings suggest that gossypetin is an MKK3 and MKK6 inhibitor that could be useful for preventing or treating esophageal cancer.

Prediction of binding potential of natural leads against the prioritized drug targets of chikungunya and dengue viruses by computational screening

The current study aimed to assess the binding potential of herbal lead molecules against the prioritized molecular targets of chikungunya virus (CHIKV) and dengue virus (DENV) by computational virtual screening and suggests a novel therapeutic intervention. Based on the metabolic pathway analysis and virulent functions, the non-structural and envelop proteins present in CHIKV and DENV were identified as putative drug targets. The structures of the protein not available in their native forms were computationally predicted by homology modeling. The lead compounds from 43 herbal sources were screened and their drug likeliness and pharmacokinetics properties were computationally predicted. The binding potential of selected phytoligands against the prioritized drug targets were analyzed by molecular docking studies. This study revealed that Kaempferol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)chromen-4-one) and Chymopain (disodium;4,5-dihydroxybenzene-1,3-disulfonate), natural flavonols present in Carica papaya and Gossypetin (3, 5, 7, 8, 3', 4'-hexahydroxyflavone), a natural flavonoid available in Hibiscus sabdariffa were demonstrated promising good binding potential with minimum binding energy (kcal/mol) and maximum stabilizing interactions to the putative drug targets of CHIKV and DENV. The selected lead molecules demonstrated ideal drug likeliness, ADMET (adsorption, distribution, excretion, metabolism and toxicity) features required for the drug development. The molecular docking studies suggested that the presence of these compounds probably responsible for the antiviral properties of Carica papaya, which was traditionally known as therapeutic remedy for dengue viral infections. This study provides profound insight for the experimental validation of the applied approach and industrial scale-up of the suggested herbal lead molecules as promising lead candidates against CHIKV and DENV infections.

Flavonoids as Multi-target Inhibitors for Proteins Associated with Ebola Virus: In Silico Discovery Using Virtual Screening and Molecular Docking Studies

Ebola virus is a single-stranded, negative-sense RNA virus that causes severe hemorrhagic fever in humans and non-human primates. This virus is unreceptive to a large portion of the known antiviral drugs, and there is no valid treatment as on date for disease created by this pathogen. Looking into its ability to create a pandemic scenario across globe, there is an utmost need for new drugs and therapy to combat this life-threatening infection. The current study deals with the evaluation of the inhibitory activity of flavonoids against the four selected Ebola virus receptor proteins, using in silico studies. The viral proteins VP40, VP35, VP30 and VP24 were docked with small molecules obtained from flavonoid class and its derivatives and evaluated on the basis of energetics, stereochemical considerations and pharmacokinetic properties to identify potential lead compounds. The results showed that both top-ranking screened flavonoids, i.e., Gossypetin and Taxifolin, showed better docking scores and binding energies in all the EBOV receptors when compared to those of the reported compound. All the screened flavonoids have known antiviral activity, acceptable pharmacokinetic properties and are being used on human and thus can be taken as anti-Ebola therapy without the time lag for clinical trial.