Berberine: A Review of its Pharmacokinetics Properties and Therapeutic Potentials in Diverse Vascular Diseases

Myocardial Ischemia

Inflammation is one of the most observed cardiovascular conditions, and has a significant role in the progression of CVD (Golia et al., 2014; Lockshin et al., 2018). Aggravating inflammation may induce vascular remodeling after myocardial ischemia (MI), contributing to reduction of the ejection fraction and subsequent heart failure (Lu et al., 2015; Chong et al., 2021). It has been suggested that 50 mg/kg berberine may improve vascular inflammation and remodeling by inhibiting p38 mitogen-activated protein kinase (MAPK) activation, and activating transcription factor 2 phosphorylation (p-ATF-2) and matrix metalloprotease 2 (MMP-2) expression in rats (Li et al., 2015a). Protein hyperacetylation is associated with the development of MI (Treviño-Saldaña and García-Rivas, 2017; Aggarwal et al., 2020). Accumulating studies have demonstrated that silent information regulator 1 (SIRT-1) can regulate oxidative stress and inflammation to inhibit the development and progression of cardiac dysfunction in myocardial ischemia/reperfusion (MI/R) injury (Xue et al., 2020; Chang et al., 2021). Owing to its strong antioxidative and anti-inflammatory activities, oral administration of berberine (200 mg/kg) conferred cardioprotective effects in rats by improving post-MI/R cardiac function recovery and reducing infarct size after MI/R injury; the mechanism of action was found to be associated with the regulation of the SIRT-1 signaling pathway (Yu et al., 2016). As a selective barrier between tissue and blood, endothelial cells play a potential role in the control of inflammatory responses and homeostasis (Krüger-Genge et al., 2019). Endothelial cell dysfunction and/or injury can disrupt the integrity of the endothelial lining and subsequently lead to vascular disease, such as MI (Monteiro et al., 2019). Additionally, large experimental studies suggest that excessive inflammation can directly lead to endothelial cell apoptosis (Bravo-San Pedro et al., 2017; Henning et al., 2018). Lipopolysaccharide (LPS)-induced inflammation and apoptosis in human umbilical vein endothelial cells (HUVECs) were found to be inhibited by pretreatment with 5 μM berberine, mediated by inhibition of c-Jun N-terminal kinase (JNK) phosphorylation, and increased myeloid cell leukemia 1 (MCL-1) expression and superoxide dismutase (SOD) activity (Guo et al., 2016).

Angiogenesis, the formation of new blood vessels from preexisting ones, is indispensable for revascularization and cardiac remodeling following MI (Mathiyalagan et al., 2019; Chong et al., 2021; Tang et al., 2021). Ischemic heart disease is a leading cause of mortality and results from vascular cavity stenosis and occlusion (Garry et al., 2021). Rehabilitation of the myocardial ischemic region involves the activation of several stimulatory and inhibitory modulators of angiogenesis; the most notable of which are vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF-2), and thrombospondin 1 (TSP-1) (Detillieux et al., 2003; Frangogiannis et al., 2005; Martinez et al., 2018; Garikipati et al., 2019). Treatment with 10 mg/kg of berberine-rich extract (5 days a week by gavage) remarkably reduced heart infarct size, and increased the expression of angiogenesis-promoting factors in rats with MI/R injury, including VEGF, FGF-2 and TSP-1 (Banaei et al., 2020). In addition, microRNA plays a key role in many cardiac pathological processes, including MI (Parikh et al., 2020). Treatment with berberine in mice with MI injury was shown to lead to elevated miR-29b can activate the protein kinase B (Akt) signaling pathway, thus promoting angiogenesis and cell proliferation and migration to improve heart function (Zhu et al., 2017). A study in zebrafish embryos revealed that the level of VEGF-aa mRNA was up-regulated by berberine, which interfered with the angiogenic process, promoting bradycardia and reducing the cardiac output, atrial shortening fraction percentage, and atrial stroke volume (Martini et al., 2020). A complex hemodynamic pathological phenomenon exists in ischemia and reperfusion injury that can engage the metabolic and inflammatory machinery in the development of various disorders, including heart failure (Raza et al., 2020). Interestingly, intragastric administration of 100 mg/kg berberine daily for 14 days attenuated ischemia–reperfusion injury via hemodynamic improvements and inhibition of AMPK activity in both non-ischemic and ischemic areas of rat heart tissue (Chang et al., 2012).

Recent evidence has confirmed that endoplasmic reticulum (ER) stress is correlated with the development and progression of various heart diseases including cardiac hypertrophy, ischemic heart diseases, and heart failure (Wang et al., 2018). Prolonged ER stress, however, can become a leading cause of vascular endothelial cell dysfunction and apoptosis in CVD (Chen et al., 2020; Fatima et al., 2021). Oral administration of 200 mg/kg berberine daily for 2 weeks was reported to protect the heart from MI/R injury in rats by activating the janus kinase 2 (JAK-2)/signal transducer and activator of transcription 3 (STAT-3) signaling pathway, as well as by attenuating ER stress-induced apoptosis (Zhao et al., 2016). Alternatively, apoptosis and inflammation are correlated with anoxia-reoxygenation injury in CVD, which typically occurs during MI (Huang et al., 2018; Gan et al., 2020). The decreased inflammatory cytokines and myocardial cell apoptosis resulting from berberine administration may alleviate anoxia-reoxygenation injury by downregulating p38 MAPK-mediated nuclear factor κB (NF-κB) signaling pathway (Zhao et al., 2019c). In conclusion, given its robust anti-inflammatory, antioxidative stress, antiapoptotic, and anti-ER stress effects, berberine may effectively improve CDV and MI by inhibiting the MAPK, AMPK and NF-κB pathways and activating PPARα-NO, VEGF, and JAK-2/STAT-3 pathways (Figure 3 and Table 1).

Atherosclerosis

Atherosclerosis is a leading cause of death worldwide, and is characterized by lipid deposition, chronic inflammatory injury, smooth muscle cell proliferation, and plaque formation (Insull, 2009; Wolf and Ley, 2019). The pathological process of atherosclerosis begins with endothelial damage, accompanied by abnormal migration of VSMCs, leading to vascular remodeling (Sitia et al., 2010; Liang et al., 2020). Administration of 25, 50 and 100 μM berberine may suppress the expression of MMP-2, MMP-9 and urokinase-type plasminogen activator (u-PA) to significantly inhibit fetal bovine serum-induced human aortic smooth muscle cell (HASMC) migration, which may act to interrupt the activator protein 1 (AP-1) and NF-κB signaling pathways (Liu et al., 2014). Dysregulation of lipid metabolism is considered another major risk factor for atherosclerosis (Agrawal et al., 2018). An expert committee published the National Cholesterol Education Program in United States, emphasizing that low density lipoprotein (LDL) should be the primary target of cholesterol-lowering therapy in atherosclerosis (Tavares et al., 2021). In particular, clinical trials have demonstrated that lowering LDL levels can reduce the risk of atherosclerosis (Ference et al., 2017; Ji and Lee, 2021). Notably, the increased lipid in the serum and liver was reduced with the administration of berberine, which improved intima-media thickening, restored aortic endothelium-dependent vasodilatation, and alleviated atherosclerotic lesions in APOE^(−/−) mice fed a western-type diet for 12 weeks (Tan et al., 2020). Similarly, berberine ameliorated high-fat diet (HFD)-induced hyperlipidemia and lipid accumulation in liver and adipose tissue, alleviated endothelial lesions and reduced the expression of inflammatory cytokines in the plasma of APOE^(−/−) mice; it also reduced cholesteryl ester gathering in the aortic arch, resulting in ameliorated arterial plaque build-up via altered AMPK and NF-κB gene expression, and interrupted crosstalk between adipocytes and macrophages (Ma et al., 2020).

Tumor necrosis factor α (TNF-α) is a major proinflammatory factor in the development of vascular inflammation (Jang et al., 2017). Aberrant inflammatory responses may result in the ablation of macrophages, aggravation of vascular endothelial injury, and abnormal tissue proliferation in atherosclerosis (Hui et al., 2010; Brown et al., 2017). In vitro studies have indicated that TNF-α-induced inflammation, which causes excessive expression of intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein 1 (MCP-1) could be decreased by berberine in human aortic endothelial cells; this may be associated with inhibition of the NF-κB and AMPK pathways (Liu et al., 2015b). Oxidized LDL (ox-LDL) can act as an antigen to activate the immune inflammatory response, increasing the infiltration of inflammatory cells and the secretion of inflammatory factors in atherosclerosis (Lundberg et al., 2021). Ox-LDL-induced HUVEC proliferation and inflammatory responses were reversed with berberine, which lowered the expression of proliferating cell nuclear antigen (PCNA), NF-кB, and lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1), and inhibited the phosphoinositide 3-kinase (PI3K)/Akt, extracellular signal-regulated kinase 1/2 (ERK-1/2), and p38 MAPK pathways (Xu et al., 2017). Ox-LDL has also been shown to injure endothelial cells directly, and contributes to endothelial dysfunction via overexpression of LOX-1, which induces a further rise in intracellular reactive oxygen species (ROS) (Kattoor et al., 2019; Akhmedov et al., 2021). Orally administrated at 156 mg/kg, berberine improved endothelial dysfunction by reducing aortic ROS generation and the release of inflammatory cytokines in the serum of a mouse model of atherosclerosis (Tan et al., 2020). Additionally, platelet–endothelial cell interactions potentiated by oxidative stress are thought to contribute to early atherosclerosis (Brown et al., 2021). Existing inflammatory and oxidative suppression of berberine prevented the development of the atherosclerotic plaque area by inhibiting translocation of NF-κB to the nucleus (Feng et al., 2017). Uncoupling protein 2 (UCP-2) is an inner mitochondrial membrane protein that belongs to the UCP family and plays an important role in lowering mitochondrial membrane potential and dissipating metabolic energy, preventing the accumulation of oxidative stress (Pierelli et al., 2017). Amazingly, treatment with 1 mmol/L berberine in drinking water led to suppression of oxidative stress and vascular inflammation by stimulating AMPK-dependent UCP-2 expression in mice with atherosclerosis (Wang et al., 2011). Moreover, recent studies found that the gut microbiota played a crucial role in atherosclerosis (Jonsson and Bäckhed, 2017; Verhaar et al., 2020). Another study emphasized that the modulation of gut microbiota, specifically the abundance of the Akkermansia bacterial genus, contributed to the antiatherosclerotic and metabolic protective effects of berberine by suppressing intestinal inflammation and promoting intestinal epithelial barrier integrity (Zhu et al., 2018).

Prolonged activation of the ER stress pathway can lead to aggravated oxidative stress and endothelial cell apoptosis (Tabas, 2010; Linton et al., 2016). Kawasaki disease (KD) is an acute febrile illness characterized by systemic vasculitis, especially in coronary arteries (de Ferranti et al., 2018). Berberine exerted its protective effects on KD-induced apoptosis of human coronary artery endothelial cells by inhibiting oxidative and ER stress (Xu et al., 2020). Endothelial cell apoptosis induced by ER stress is closely linked with plaque progression, which can contribute to unstable atherosclerotic plaques, perhaps in response to thrombosis in atherosclerosis (Yang et al., 2021). Homocysteine increases damage to vascular endothelial cells, thereby reducing vasodilation factors released by endothelial cells and impairing vasodilation in the endothelium, resulting in vascular endothelial apoptosis and inducing oxidation (Salvio et al., 2021). Nevertheless, an in vivo experiment has shown that berberine increased the stability of atherosclerotic plaques and mitigated detrimental effects of vascular endothelial cell activity experimentally induced by 50 mg/kg homocysteine thiolactone, and similar results are found in vitro study induced by 1 mM homocysteine thiolactone (Li et al., 2016a). Collectively, the studies presented here (Table 2) indicate that berberine may improve vascular endothelial damage, abnormal lipid metabolism, chronic inflammation, plaque formation, and cell apoptosis, thereby alleviating atherosclerosis (Figure 4).

Alzheimer’s Disease

Alzheimer’s disease (AD) is a complex, aging-related, neurodegenerative disease, and the pathology process mainly involves β-amyloid (Aβ) overproduction and accumulation, tau hyperphosphorylation, and neuronal loss (Lian et al., 2016; Spangenberg et al., 2016; Gao et al., 2018). Administration of 0.5 μM berberine significantly suppressed Aβ-induced production of interleukin 6 (IL-6) and MCP-1 by inhibiting the activation of NF-κB and blocking the PI3K/Akt and MAPK pathways (Jia et al., 2012). Accumulated Aβ can result from abnormal processing of amyloid precursor protein (APP) in AD (O'Brien and Wong, 2011). APP C-terminal fragment levels and APP and tau hyperphosphorylation were decreased with 100 mg/kg berberine, administered by oral gavage for 4 months, via the Akt/glycogen synthase kinase 3 (GSK-3) pathway in rats with AD (Durairajan et al., 2012). Similarly, berberine modulates Aβ generation through activation of the AMPK pathway in N2a mouse neuroblastoma cells (Zhang et al., 2017). Moreover, elevated Aβ can mediate synaptic loss and dysfunction, another pathological hallmark of AD, by targeting mitochondria (Hong et al., 2016). Pretreatment with 1 μM berberine alleviated axonal mitochondrial abnormalities by preserving the mitochondrial membrane potential and preventing decreases in ATP, increasing axonal mitochondrial density and length, and improving mitochondrial motility and trafficking in 0.5 μM Aβ cultured hippocampal mouse neurons (Zhao et al., 2019a). Additionally, neuronal loss and cerebral blood flow contributed to dysfunction in memory and reward systems in AD (Dai et al., 2009; Nobili et al., 2017). Studies found that drinking water containing 100 mg/L berberine exerted a strong neuroprotective effect, improving cognitive deficits, inhibiting the apoptosis of neurons, and promoting the formation of micro-vessels by restoring cerebral blood flow and reducing Aβ accumulation in an APP/tau/PS-1 mouse model of AD (Ye et al., 2021). As shown in Table 3, the potential effects of berberine observed in the study suggest that it may effectively prevent AD by reducing accumulated Aβ. Few studies have focused on the improvement of tau hyperphosphorylation and neuronal loss in AD, which should thus be a focus of future research.

Vascular Dementia

Vascular dementia (VD) is the second most common form of dementia and is caused by vascular pathologies causing brain injury (Poh et al., 2021). In a rat model of VD induced by cerebral ischemia–reperfusion injury, increased angiogenesis was observed with berberine chloride (50 mg/kg) treatment, which may be due to the activation of hypoxia-inducible factor 1α (HIF-1α)/VEGF signal pathway (Liu et al., 2018). In general, few studies have focused on the relationship between berberine and vascular in VD. According to the development of new biological in recent years, imaging technology is conducive to strengthen the study of berberine and cerebrovascular diseases. Second near-infrared II (NIR-II) imaging, a kind of biomedical imaging technology with characteristics of high sensitivity, high resolution, and real-time imaging, can visualize the vasculature in the brain (Guo et al., 2019a). Therefore, we can directly utilize the NIR-II to observe the improvement of the vascular in the brain by treatment with berberine.

Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is closely associated with extensive vascular remodeling, especially pulmonary arterial medial hypertrophy and muscularization, due to aberrant proliferation of pulmonary artery smooth muscle cells (PASMCs) resulting from hypoxia (Bisserier et al., 2021; Sharifi Kia et al., 2021). Hemodynamic and pulmonary pathological data showed that chronic hypoxia notably elevated the median width of pulmonary arterioles (Choudhary et al., 2011; Khoramzadeh et al., 2019). However, berberine substantially decreased pulmonary vascular remodeling in mice with hypoxia-induced PAH by inhibiting Akt/mammalian target of rapamycin (mTOR)/HIF-1α and transforming growth factor β (TGF-β) pathways, and activating bone morphogenetic protein type 2 (BMPR-2) receptor (Chen et al., 2019; Liu et al., 2019). Wande et al. (2020) demonstrated substantial proliferative activities in hypoxia-induced human PASMCs, were possibly mediated by berberine (at concentrations of 10 μM) via inhibiting the thioredoxin (TRX-1) and β-catenin pathways. Activation of protein phosphatase 2A (PP2A) has been shown to induce apoptosis of PASMCs in people with PAH (Ferron et al., 2011). Berberine may prominently attenuate proliferation and migration of PASMCs induced by norepinephrine, alleviating PAH via PP2A pathway (Luo et al., 2018). These results together show that berberine significantly suppresses pulmonary vascular remodeling and proliferation of vascular endothelial cells in PAH; the antiproliferative and antiapoptotic effects may be mediated by inhibition of the Akt/mTOR/HIF-1α and PP2A pathways (Table 4).

Diabetes Mellitus

The main cause of DM and associated complications is a low level or lack of pancreatic islet function, including insulin resistance, resulting in disordered glucose metabolism in the body (Pearson, 2019; Han et al., 2021b). Sustained hyperglycemia progresses to various diabetic microangiopathies, including diabetic cardiovascular disease, nephropathy, neuropathy and retinopathy (Reddy et al., 2015; Montero et al., 2019; Tang and Yiu, 2020). Chronic inflammation caused by hyperglycemia is a major feature of DM (Saltiel and Olefsky, 2017). Adipose tissue macrophages (ATMs), including M1 ATMs, can induce inflammatory responses by producing pro-inflammatory cytokines such as TNF-α and IL-6, thus contributing to the induction of insulin resistance in DM (Russo and Lumeng, 2018). Oral berberine (50 mg/kg/day) markedly improved insulin resistance, reduced the inflammation and JNK, IKK-β, and NF-κB p65 phosphorylation by inhibiting M1 macrophage activation in adipose tissue (Ye et al., 2016). Owing to increased aldose reductase (AR) and NADPH oxidase (NOX) activities, platelet hyperreactivity and apoptosis during DM accounts for the accumulation of ROS (Vara et al., 2019; Ajjan et al., 2021). It was demonstrated that 50 mM glucose induced platelet aggregation, apoptosis and superoxide production, which was neutralized by 25 and 50 μM berberine via inhibiting of AR, NOX and GSH reductase activities (Paul et al., 2019). Similarly, 25 μM berberine had protective effects against endothelial injury by attenuating the generation of ROS, cellular apoptosis, NF-κB activation, and expression of adhesion molecules, which were induced by high glucose levels; it also enhanced the endothelium-dependent vasodilatation through the activation of the AMPK pathway (Wang et al., 2009).

Advanced glycation end products (AGEs) are produced via the nonenzymatic glycation reaction and are considered major pathogenic factors that trigger vascular complications in diabetes (Azegami et al., 2021). Incubation with 5 or 10 μg/ml berberine significantly inhibited AGE formation in high-glucose-AGEs-induced micro-endothelial injuries (Hao et al., 2011). Diabetic peripheral neuropathy, characterized by perivascular neuropathy, is reported to be involved in vascular disorders associated with diabetes (Olesen et al., 2021). The mesenteric artery, a part of the splanchnic circulation system, is involved in the regulation of arterial pressure (van Dijk et al., 2020). The iliac artery is mainly responsible for blood supply to the lower extremities and pelvic organs (Maier et al., 2020). Both of these sites are predisposed to large vascular lesions in diabetes. Oral administration of 200 mg/kg berberine markedly enhanced the nitrergic neural activity in the superior mesenteric artery and diminished the adrenergic function in the iliac artery, resulting in vasodilatation in diabetic rats (Geng et al., 2016; Zhao et al., 2019b).

Intracellular Ca²⁺, which is tightly controlled by Ca²⁺ channels and transporters, is an important messenger in VSMC dedifferentiation (Nagel et al., 2006). Elevated concentrations of intracellular Ca²⁺ is a primary stimulus for smooth muscle contraction; it is reported that diabetic vascular dysfunction is tightly coupled to the impairment of intracellular Ca²⁺ processing in VSMCs (Searls et al., 2010; Yang et al., 2020). Impaired cerebral arterial vasodilation can be alleviated by berberine in a diabetic rat model via down-regulation of the intracellular Ca²⁺ processing of VSMCs (Ma et al., 2016). Hyperglycemia and hypertension are the two primary risk factors for vascular disease in diabetic patients (Cryer et al., 2016; Petrie et al., 2018). Increases in intracellular Ca²⁺ along with decreases in K⁺ can lower the membrane potential and enhance the vasoconstriction response and the proliferation of VSMCs, leading to hypertension (Seki et al., 2017; Sun et al., 2021). Chronic administration of 100 mg/kg berberine reduced blood pressure and improved vasodilation in diabetic rats by activating the Ca²⁺-activated K⁺ channel (Ma et al., 2017). Aberrant miR-133a expression in endothelial cells induces endothelial dysfunction and impaired endothelium-dependent vasodilation, aggravating the pathogenesis of cerebrovascular diseases (Li et al., 2016b). Administration of berberine (1.0 g/kg for 8 weeks) reduced miR-133a expression and impairments in learning and memory, increasing the vasodilation in the middle cerebral artery to improve VD associated with diabetes (Yin et al., 2019). Furthermore, existing evidence suggests that hyperglycemia and hypoxia can trigger cerebrovascular dysfunction (Lefferts et al., 2016; Jin et al., 2019). Berberine at a concentration of 30 μM counteracted the attenuating effects of hypoxic/high-glucose conditions on the proliferation and migration of rat brain microvascular endothelial cells, which was in part mediated by the SIRT-1/HIF-1α/VEGF pathway (Mi et al., 2019). According to these studies, berberine had a hypoglycemic effect through improving insulin resistance, and has robust anti-inflammatory, antiapoptotic and antiendothelial injury effects in DM. Berberine appears to improve endothelial dysfunction by regulating Ca²⁺ and K⁺ channels in DM (Table 5).

Diabetic Retinopathy

Diabetic retinopathy (DR) is a retinal microvascular disease caused by chronic hyperglycemia leading to angiogenesis in retina (Ai et al., 2019). In recent years, improvement of disordered glucolipid metabolism is considered one of the most effective strategies for the treatment of DM and its complications (Zhao et al., 2021b). Berberine has been shown to block DR development by modulating the glucolipid metabolism and inhibiting the HIF-1α/VEGF/NF-κB pathway (Yin et al., 2021). The pathological processes involved in DR may be related to increased levels of pro-inflammatory factors, leading to oxidative stress and the apoptotic cascade (Ai et al., 2020; Robles-Rivera et al., 2020; Gong et al., 2021). Berberine may deactivate the NF-κB pathway, thus suppressing oxidative stress and cell apoptosis in DR (Zhai et al., 2020). As a major energy receptor and metabolic regulator, AMPK is one of the therapeutic targets for metabolic and vascular diseases (Lu et al., 2019). 10 or 20 μM berberine was shown to have therapeutic effects, protecting Müller cells from 30 mM glucose-induced apoptosis by enhancing autophagy and activating the AMPK/mTOR pathway in DR (Chen et al., 2018). These results together indicate that berberine could attenuate the pathogenesis of DR, mainly through regulating the HIF-1α/VEGF/NF-κB and AMPK/mTOR pathways to inhibit microvascular proliferation, oxidative stress and apoptosis (Table 5).

Diabetic Nephropathy

Diabetic nephropathy (DN), one of the most serious microvascular complications of DM, is the leading cause of end-stage renal failure (Lai et al., 2018). The early stage of DN is mainly characterized by abnormal renal hemodynamics, which mainly manifests as decreased vascular resistance in the glomerulus (Toledo et al., 2015). Research has shown that accumulation of ECM production in the glomerular mesangial membrane may be related to NF-κB pathway (Gong et al., 2020). The ameliorative effects of berberine (300 mg/kg) on ECM accumulation may be due to decreased TGF-β1 and ICAM-1 resulting from inhibition of the NF-κB pathway, as shown in a rat model of DN (Liu et al., 2010a). Recent studies have shown that abnormal levels of β-arrestins, including β-arrestins 1 and 2, have a role in microvascular permeability by regulating the production and function of ICAM-1 and vascular cell adhesion molecule 1 (VCAM-1) in the kidneys of a rat model of DN (Noh et al., 2017; Zhang et al., 2018). Orally administration of 100 or 200 mg/kg berberine had renoprotective effects owing to decreased ICAM-1 and VCAM-1 levels and increased β-arrestin 1 and 2 in kidneys of a rat model of DN (Tang et al., 2016). Additionally, inflammation in the kidney is another aggravating factor renal vascular damage in DN (Moreno et al., 2018). Berberine may attenuate LPS-induced inflammation and extracellular matrix accumulation via the NF-κB signaling pathway (Jiang et al., 2011). Given its robust antihyperglycemic and anti-inflammatory activities, and its inhibitory effect on angiogenesis, berberine should be considered a candidate drug for DN (Table 5).