Stevioside inhibits experimental fibrosis by down-regulating profibrotic Smad pathways and blocking hepatic stellate cell activation

Natural Products in Liver Fibrosis Management: A Five-year Review

Liver fibrosis, characterized by the overproduction of extracellular matrix proteins within liver tissue, poses a rising global health concern. However, no approved antifibrotic drugs are currently available, highlighting the critical need for understanding the molecular mechanisms of liver fibrosis. This knowledge could not only aid in developing therapies but also enable early intervention, enhance disease prediction, and improve our understanding of the interaction between various underlying conditions and the liver. Notably, natural products used in traditional medicine systems worldwide and demonstrating diverse biochemical and pharmacological activities are increasingly recognized for their potential in treating liver fibrosis. This review aims to comprehensively understand liver fibrosis, emphasizing the molecular mechanisms and advancements in exploring natural products' antifibrotic potential over the past five years. It also acknowledges the challenges in their development and seeks to underscore their potency in enhancing patient prognosis and reducing the global burden of liver disease.

Stevioside attenuates bleomycin-induced pulmonary fibrosis by activating the Nrf2 pathway and inhibiting the NF-κB and TGF-β1/Smad2/3 pathways

Objective: This study aimed to investigate the effects of stevioside (STE) on pulmonary fibrosis (PF) and the potential mechanisms. Methods: In this study, a mouse model of PF was established by a single intratracheal injection of bleomycin (BLM, 3 mg/kg). The experiment consisted of four groups: control group, BLM group, and STE treatment groups (STE 50 and 100 mg/kg). ELISA and biochemical tests were conducted to determine the levels of TNF-α, IL-1β, IL-6, NO, hydroxyproline (HYP), SOD, GSH, and MDA. Histopathological changes and collagen deposition in lung tissues were observed by HE and Masson staining. Immunohistochemistry was performed to determine the levels of collagen I-, collagen III-, TGF-β1- and p-Smad2/3-positive cells. Western blot analysis was used to measure the expression of epithelial-mesenchymal transition (EMT) markers, including α-SMA, vimentin, E-cadherin, and ZO-1, as well as proteins related to the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, nuclear transcription factor-κB (NF-κB) pathway, and TGF-β1/Smad2/3 pathway in lung tissues. Results: STE significantly alleviated BLM-induced body weight loss and lung injury in mice, decreased HYP levels, and reduced the levels of collagen I- and collagen III-positive cells, thereby decreasing extracellular matrix (ECM) deposition. Moreover, STE markedly improved oxidative stress (MDA levels were decreased, while SOD and GSH activity were enhanced), the inflammatory response (the levels of TNF-α, IL-1β, IL-6, and NO were reduced), and EMT (the expression of α-SMA and vimentin was downregulated, and the expression of E-cadherin and ZO-1 was upregulated). Further mechanistic analysis revealed that STE could activate the Nrf2 pathway and inhibit the NF-κB and TGF-β1/Smad2/3 pathways. Conclusion: STE may alleviate oxidative stress by activating the Nrf2 pathway, suppress the inflammatory response by downregulating the NF-κB pathway, and inhibit EMT progression by blocking the TGF-β1/Smad2/3 pathway, thereby improving BLM-induced PF.

Stevioside targets the NF-κB and MAPK pathways for inhibiting inflammation and apoptosis of chondrocytes and ameliorates osteoarthritis in vivo

Osteoarthritis (OA) is a joint disease that is characterized by articular cartilage degeneration and destruction. Stevioside (SVS) is a diterpenoid glycoside extracted from Stevia rebaudiana Bertoni with some specific effects against inflammatory and apoptotic, whereas it is still unclear what function SVS has in osteoarthritis. This study focuses on the anti-inflammatory and anti-apoptosis functions of SVS on chondrocytes induced by interleukin (IL)-1beta, and the role of SVS in an osteoarthritis model for mice. We can detect the production of inflammatory factors such as nitric oxide (NO) and prostaglandin E2 (PGE2) using real-time quantitative polymerase chain reaction (RT-qPCR), the Griess reaction, and enzyme linked immunosorbent assay (ELISA). On the basis of Western blot, we have observed the protein expressions of cartilage matrix metabolism, inflammatory factors, and apoptosis of chondrocytes. Simultaneously, the pharmacological effects of SVS in mice were evaluated by hematoxylin and eosin (HE), toluidine blue, Safranin O, and immunohistochemical staining. The results show that SVS slows extracellular matrix degradation and chondrocyte apoptosis. In addition, SVS mediates its cellular effect by inhibiting the activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signaling pathways. Meanwhile, molecular docking studies revealed that SVS has excellent binding capabilities to p65, extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK). The study suggests that SVS can be developed as a potential osteoarthritis treatment.

Free radicals, antioxidants, nuclear factor-E2-related factor-2 and liver damage

The liver performs various biochemical and molecular functions. Its location as a portal to blood arriving from the intestines makes it susceptible to several insults, leading to diverse pathologies, including alcoholic liver disease, viral infections, nonalcoholic steatohepatitis, and hepatocellular carcinoma, which are causes of death worldwide. Illuminating the molecular mechanism underlying hepatic injury will provide targets to develop new therapeutic strategies to fight liver maladies. In this regard, reactive oxygen species (ROS) are well-recognized mediators of liver damage. ROS induce nuclear factor-κB and the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 inflammasome, which are the main proinflammatory signaling pathways that upregulate several proinflammatory and profibrogenic mediators. Additionally, oxygen-derived free radicals induce hepatic stellate cell activation to produce exacerbated quantities of extracellular matrix proteins, leading to fibrosis, cirrhosis and eventually hepatocellular carcinoma. Exogenous and endogenous antioxidants counteract the harmful effects of ROS, preventing liver necroinflammation and fibrogenesis. Therefore, several researchers have demonstrated that the administration of antioxidants, mainly derived from plants, affords beneficial effects on the liver. Notably, nuclear factor-E2-related factor-2 (Nrf2) is a major factor against oxidative stress in the liver. Increasing evidence has demonstrated that Nrf2 plays an important role in liver necroinflammation and fibrogenesis via the induction of antioxidant response element genes. The use of Nrf2 inducers seems to be an interesting approach to prevent/attenuate hepatic disorders, particularly under conditions where ROS play a causative role.

Oxycodone/naloxone versus tapentadol in real-world chronic non-cancer pain management: an observational and pharmacogenetic study

Tapentadol (TAP) and oxycodone/naloxone (OXN) potentially offer an improved opioid tolerability. However, real-world studies in chronic non-cancer pain (CNCP) remain scarce. Our aim was to compare effectiveness and security in daily pain practice, together with the influence of pharmacogenetic markers. An observational study was developed with ambulatory test cases under TAP (n = 194) or OXN (n = 175) prescription with controls (prescribed with other opioids (control), n = 216) CNCP patients. Pain intensity and relief, quality of life, morphine equivalent daily doses (MEDD), concomitant analgesic drugs, adverse events (AEs), hospital frequentation and genetic variants of OPRM1 (rs1799971, A118G) and COMT (rs4680, G472A) genes, were analysed. Test CNCP cases evidenced a significantly higher pain relief predictable due to pain intensity and quality of life (R2 = 0.3), in front of controls. Here, OXN achieved the greatest pain relief under a 28% higher MEDD, 8-13% higher use of pregabalin and duloxetine, and 23% more prescription change due to pain, compared to TAP. Whilst, TAP yielded a better tolerability due the lower number of 4 [0-6] AEs/patient, in front of OXN. Furthermore, OXN COMT-AA homozygotes evidenced higher rates of erythema and vomiting, especially in females. CNCP real-world patients achieved higher pain relief than other traditional opioids with a better tolerability for TAP. Further research is necessary to clarify the potential influence of COMT and sex on OXN side-effects.

Stevioside inhibits lipopolysaccharide-induced epithelial-to-mesenchymal transition of NRK-52E cells by PPARγ activation

BACKGROUND

Stevioside is a natural diterpenoid compound that possesses anti-inflammatory, immunomodulatory, anti-diabetic, anti-hypertensive, and renal protective effects, but its effect on lipopolysaccharide (LPS)-induced epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells, an important immune pathological mechanism of renal fibrosis, remains unknown. This study employed the renal proximal tubular cells NRK-52E to investigate the effect of stevioside.

METHODS

The LPS-stimulated renal NRK-52E cells were treated with 50, 100, or 200 μM stevioside in the presence or absence of peroxisome proliferator-activated receptor γ (PPARγ) antagonist GW9662, the expression levels of intracellular E-cadherin, vimentin, α-smooth muscle actin (α-SMA), PPARγ, nuclear factor kappa B (NF-κB) p65, transforming growth factor-β1 (TGF-β1), signal transducer and activator of transcription 3 (STAT3), p-STAT3, Smad2/3, and p-Smad2/3 proteins were detected by Western blot analysis.

RESULTS

In LPS-stimulated NRK-52E cells, stevioside treatment could reverse the expressions of EMT-related E-cadherin, vimentin, and α-SMA proteins, increase the expression of PPARγ protein, and decrease the expressions of NF-κB p65, TGF-β1, p-STAT3, Smad2/3, and p-Smad2/3 proteins, especially in the 200 μM stevioside-treated group. However, these beneficial effects of stevioside were attenuated or canceled by pretreatment with PPARγ antagonist GW9662.

CONCLUSIONS

Stevioside can inhibit the LPS-induced EMT via the reductions of NF-κB, TGF-β1, Smad2/3, p-Smad2/3, and p-STAT3 protein expressions by PPARγ activation in NRK-52E cells, which may provide a pharmacological basis for the potential application of stevioside in the prevention and treatment of renal fibrosis.

The role of metabolites of steviol glycosides and their glucosylated derivatives against diabetes-related metabolic disorders

Diabetes mellitus (DM), characterized by abnormal carbohydrate, lipid, and protein metabolism, is a metabolic disorder caused by a shortage of insulin secretion or decreased sensitivity of target cells to insulin. In addition to changes in lifestyle, a low-calorie diet is recommended to reduce the development of DM. Steviol glycosides (SGs), as natural sweeteners, have gained attention as sucrose alternatives because of their advantages of high sweetness and being low calorie. Most SGs with multiple bioactivities are beneficial to regulate physiological functions. Though SGs have been widely applied in food industry, there is little data on their glucosylated derivatives that are glucosylated steviol glycosides (GSGs). In this review, we have discussed the metabolic fate of GSGs in contrast to SGs, and the molecular mechanisms of glycoside metabolites against diabetes-related metabolic disorders are also summarized. SGs are generally extracted from the Stevia leaf, while GSGs are mainly manufactured using enzymes that transfer glucose units from a starch source to SGs. Results from this study suggest that SGs and GSGs share same bioactive metabolites, steviol and steviol glucuronide (SVG), which exhibit anti-hyperglycemic effects by activating glucose-induced insulin secretion to enhance pancreatic β-cell function. In addition, steviol and SVG have been found to ameliorate the inflammatory response, lipid imbalance, myocardial fibrosis and renal functions to modulate diabetes-related metabolic disorders. Therefore, both SGs and GSGs may be used as potential sucrose alternatives and/or pharmacological alternatives for preventing and treating metabolic disorders.

Paeoniflorin modulates oxidative stress, inflammation and hepatic stellate cells activation to alleviate CCl4-induced hepatic fibrosis by upregulation of heme oxygenase-1 in mice

OBJECTIVES

The role of Paeoniflorin on hepatic fibrosis and the specific mechanisms has not yet been elucidated. Therefore, we explored whether Paeoniflorin exerted protective effects on carbon tetrachloride (CCl4)-induced hepatic fibrosis and the underlying mechanisms.

METHODS

A model of hepatic fibrosis was induced by intraperitoneally injecting with CCl4 (10% 5 μl/g) twice a week for 7 weeks. To explore the effects of Paeoniflorin, mice were treated with Paeoniflorin (100 mg/kg) by gavage once a day at 1 week after modeling until they were sacrificed.

KEY FINDINGS

Paeoniflorin remarkably improved liver function and histopathological changes of hepatic tissues in CCl4-induced liver injury. Besides, the serum MAO enzyme activity and hydroxyproline contents were notably decreased following the intervention of Paeoniflorin. The decreased expression of Vimentin, α-SMA, Col1a and Desmin manifested the inhibition of the hepatic stellate cells (HSCs) activation. Interestingly, Paeoniflorin intervention significantly upregulated the expression of heme oxygenase-1, and attenuated the inflammatory cytokines production as well as the CCl4-induced oxidative stress imbalance.

CONCLUSIONS

Paeoniflorin could effectively alleviate CCl4-induced hepatic fibrosis by upregulation of heme oxygenase-1, and it might be a new effective option for the comprehensive treatment of hepatic fibrosis.

Molecular Mechanisms That Link Oxidative Stress, Inflammation, and Fibrosis in the Liver

Activated hepatic stellate cells (HSCs) and myofibroblasts are the main producers of extracellular matrix (ECM) proteins that form the fibrotic tissue that leads to hepatic fibrosis. Reactive oxygen species (ROS) can directly activate HSCs or induce inflammation or programmed cell death, especially pyroptosis, in hepatocytes, which in turn activates HSCs and fibroblasts to produce ECM proteins. Therefore, antioxidants and the nuclear factor E2-related factor-2 signaling pathway play critical roles in modulating the profibrogenic response. The master proinflammatory factors nuclear factor-κB (NF-κB) and the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome may coordinate to produce and activate profibrogenic molecules such as interleukins 1β and 18, which effectively activate HSCs, to produce large amounts of fibrotic proteins. Furthermore, the NLRP3 inflammasome activates pro-caspase 1, which is upregulated by NF-κB, to produce caspase 1, which induces pyroptosis via gasdermin and the activation of HSCs. ROS play central roles in the activation of the NF-κB and NLRP3 signaling pathways via IκB (an inhibitor of NF-κB) and thioredoxin-interacting protein, respectively, thereby linking the molecular mechanisms of oxidative stress, inflammation and fibrosis. Elucidating these molecular pathways may pave the way for the development of therapeutic tools to interfere with specific targets.

Herbal medicines for the liver: from bench to bedside

The liver is one of the most complex organs of the human body and is involved in various metabolic processes. Due to its anatomical proximity to the digestive tract, its blood flow, and its contribution to the detoxification process, the liver is susceptible to a wide variety of disorders. Hepatic diseases can be caused by alcoholism, viral infections, malnutrition and xenobiotics, which result in a high frequency of patients with liver disease and subsequent increase in the number of deaths from these diseases, for which adequate treatments are not yet available. Therefore, the search for new alternatives to treat these liver conditions is mandatory. In recent decades, there has been an increase in interest in medicinal herbs due to their safety and hepatoprotective properties that arise from their anti-inflammatory, antioxidant, antifibrotic, antiviral, immunomodulatory and anticancer properties. Epidemiological and clinical studies have shown that the consumption of these compounds is associated with a decrease in the risk of developing liver diseases; thus, medicinal herbs have emerged as a viable option for the treatment of these hepatic pathologies. However, more basic and clinical studies are needed before reaching a final recommendation to treat human liver diseases. This review provides molecular and clinical information on some natural compounds and medicinal herbs that have hepatoprotective effects and could be useful for the treatment of hepatic disorders.

Proteasome inhibitor MG132 inhibits the process of renal interstitial fibrosis

The proteasome inhibitor pathway serves a crucial role in cell cycle progression and apoptosis, and in the activation of transcription factors and cytokines in tumor cells. The aim of the current study was to investigate the effect of the proteasome inhibitor, MG132, on transforming growth factor (TGF)-β1-induced expression of extracellular matrix proteins in rat renal interstitial fibroblasts (NRK-49F cells) and to better elucidate the mechanism by which MG132 functions. The level of connective tissue growth factor (CTGF), α-smooth muscle actin (SMA), fibronectin (FN) and collagen type III (Col III) in the MG132-pretreated groups was significantly decreased compared with groups treated with TGF-β1 alone. MG132 significantly decreased mRNA and the protein levels of fibrosis-associated factors induced by TGF-β1 treatment. The MG132-pretreated groups exhibited lower phosphorylated-mothers against decapentaplegic homolog (p-Smad)2, p-Smad3 and FN protein expression compared with the groups treated with TGF-β1 alone. In conclusion, MG132 reduced mRNA and protein expression of fibrosis-associated factors. It can successfully inhibit the inflammatory reaction induced by TGF-β via the Smad signaling pathway. These results indicate that MG132 appears to have a potent effect in counteracting renal fibrosis. MG132 may be applied in the treatment of patients with chronic kidney disease.

Rebaudioside A administration prevents experimental liver fibrosis: an in vivo and in vitro study of the mechanisms of action involved

Rebaudioside A (Reb A) is a diterpenoid isolated from the leaves of Stevia rebaudiana (Bertoni) that has been shown to possess pharmacological activity, including anti-inflammatory and antioxidant properties. However, the ability of Reb A to prevent liver injury has not been evaluated. Therefore, we aimed to study the potential of Reb A (20 mg/kg; two times daily intraperitoneally) to prevent liver injury induced by thioacetamide (TAA) administration (200 mg/kg; three times per week intraperitoneally). In addition, cocultures were incubated with either lipopolysaccharide or ethanol. Antifibrotic, antioxidant and immunological responses were evaluated. Chronic TAA administration produced considerable liver damage and distorted the liver parenchyma with the presence of prominent thick bands of collagen. In addition, TAA upregulated the expression of α-smooth muscle actin, transforming growth factor-β1, metalloproteinases 9, 2 and 13, and nuclear factor kappaB and downregulated nuclear erythroid factor 2. Reb A administration prevented all of these changes. In cocultured cells, Reb A prevented the upregulation of genes implicated in fibrotic and inflammatory processes when cells were exposed to ethanol and lipopolysaccharide. Altogether, our results suggest that Reb A prevents liver damage by blocking oxidative processes via upregulation of nuclear erythroid factor 2, exerts immunomodulatory effects by downregulating the nuclear factor-κB system and acts as an antifibrotic agent by maintaining collagen content.

Antioxidant and immunomodulatory activity induced by stevioside in liver damage: In vivo, in vitro and in silico assays

AIMS

Stevioside is a diterpenoid obtained from the leaves of Stevia rebaudiana (Bertoni) that exhibits antioxidant, antifibrotic, antiglycemic and anticancer properties. Therefore, we aimed to study whether stevioside has beneficial effects in liver injury induced by long-term thioacetamide (TAA) administration and investigated the possible underlying molecular mechanism using in vivo, in vitro and in silico approaches.

MAIN METHODS

Liver injury was induced in male Wistar rats by TAA administration (200 mg/kg), intraperitoneally, three times per week. Rats received saline or stevioside (20 mg/kg) twice daily intraperitoneally. In addition, cocultures were incubated with either lipopolysaccharide or ethanol. Liver injury, antioxidant and immunological responses were evaluated.

KEY FINDINGS

Chronic TAA administration induced significant liver damage. In addition, TAA upregulated the protein expression of nuclear factor (NF)-κB, thus increasing the expression of proinflammatory cytokines and decreasing the antioxidant capacity of the liver through downregulation of nuclear erythroid factor 2 (Nrf2). Notably, stevioside administration prevented all of these changes. In vitro, stevioside prevented the upregulation of several genes implicated in liver inflammation when cocultured cells were incubated with lipopolysaccharide or ethanol. In silico assays using tumor necrosis factor receptor (TNFR)-1 and Toll-like receptor (TLR)-4-MD2 demonstrated that stevioside docks with TNFR1 and TLR4-MD2, thus promoting an antagonistic action against this proinflammatory mediator.

SIGNIFICANCE

Collectively, these data suggest that stevioside prevented liver damage through antioxidant activity by upregulating Nrf2 and immunomodulatory activity by blocking NF-κB signaling.