Protective effect of berberine against LPS-induced injury in the intestine: a review

ABSTRACT

Sepsis is a systemic inflammatory condition caused by an unbalanced immunological response to infection, which affects numerous organs, including the intestines. Lipopolysaccharide (LPS; also known as endotoxin), a substance found in Gram-negative bacteria, plays a major role in sepsis and is mostly responsible for the disease’s morbidity and mortality. Berberine is an isoquinoline alkaloid found in a variety of plant species that has anti-inflammatory properties. For many years, berberine has been used to treat intestinal inflammation and infection. Berberine has been reported to reduce LPS-induced intestinal damage. The potential pathways through which berberine protects against LPS-induced intestinal damage by inhibiting NF-κB, suppressing MAPK, modulating ApoM/S1P pathway, inhibiting COX-2, modulating Wnt/Beta-Catenin signaling pathway, and/or increasing ZIP14 expression are reviewed.

Abbreviations: LPS, lipopolysaccharide; TLR, Toll-like receptor; MD-2, myeloid differentiation factor 2; CD14, cluster of differentiation 14; LBP, lipopolysaccharide-binding protein; MYD88, myeloid differentiation primary response 88; NF-κB, nuclear factor kappa light-chain enhancer of activated B cells; MAPK, mitogen-activated protein kinase; IL, interleukin; TNFα, tumor necrosis factor-alpha; Caco-2, cyanocobalamin uptake by human colon adenocarcinoma cell line; MLCK, myosin light-chain kinase; TJ, tight junction; IκBα, nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha; IBS, irritable bowel syndrome; ERK, extracellular signal-regulated kinase; JNK, c-Jun N-terminal kinase (JNK; GVB, gut-vascular barrier; ApoM, apolipoprotein M; S1P, sphingosine-1-phosphate; VE-cadherin, vascular endothelial cadherin; AJ, adherens junction; PV1, plasmalemma vesicle-associated protein-1; HDL, high-density lipoprotein; Wnt, wingless-related integration site; Fzd, 7-span transmembrane protein Frizzled; LRP, low-density lipoprotein receptor-related protein; TEER, transendothelial/transepithelial electrical resistance; COX-2, cyclooxygenase-2; iNOS, inducible nitric oxide synthase; IGF, insulin-like growth factor; IGFBP, insulin-like growth factor-binding protein; ZIP, Zrt-Irt-like protein; PPAR, peroxisome proliferator-activated receptors; p-PPAR, phosphorylated-peroxisome proliferator-activated receptors; ATF, activating transcription factors; SOD, superoxide dismutase; GSH-Px, glutathione peroxidase; SARA, subacute ruminal acidosis; IPEC-J2, porcine intestinal epithelial cells; ALI, acute lung injury; ARDS, acute respiratory distress syndrome

KEYWORDS:

• Berberine
• sepsis
• LPS
• intestine

1. Introduction

Sepsis is a condition that develops when the body’s immune system reacts to an infection destructively [1], often causing a cascade of events that damage multiple organ systems potentially causing organ failure and even death. Sepsis presents with a range of signs and symptoms [2]. Fever, hypotension with insufficient tissue perfusion, and disseminated intravascular coagulation are all signs of Gram-negative infection and septicemia that can lead to mortality [3]. Multiple organ dysfunctions, such as acute lung injury (ALI), acute respiratory distress syndrome (ARDS), significant myocardial depression microvascular dysfunction, acute liver function, brain microabscesses, alterations in brain neurotransmitters, and reduced cerebral blood flow, make sepsis a severe condition with considerable morbidity and mortality [4–7]. Regarding the failure of conventional treatments and subsequently significant morbidity and mortality, various attempts have been made to enhance the understanding of the host response dysregulation in sepsis [1].

Endotoxins, DNA, and peptidoglycan, which are found in gram-negative bacteria, may have a role in causing deadly septic shock [8]. The most effective microbial mediators in the pathophysiology of sepsis are the lipopolysaccharides (LPS). The Gram-negative cell wall is composed of a thin, inner layer of peptidoglycan and an outer membrane consisting of molecules of phospholipids, lipopolysaccharides (LPS), lipoproteins, and surface proteins [9]. LPS comprises three covalently connected regions: lipid A, an oligosaccharide core, and an O side chain. The toxicity of LPS resides in the innermost layer, the lipid A, which is composed of fatty acyl chains connected to two N-acetyl glucosamine residues [10]. Small levels of LPS generated by infecting pathogens trigger the potent innate immune response, preparing the immune system to defend against infection. However, if the LPS-related reaction is not appropriately managed, septic shock syndrome, which could be lethal, may develop [11].

One of the most significant organs affected by sepsis is the gastrointestinal tract [12]. Although a large number of bacteria live in the intestine, they generally do not enter the bloodstream. Intestinal mucosal integrity helps to maintain this physiological homeostasis [13]. Damaging factors such as severe burns or sepsis can launch a series of reactions leading to the breakdown of the intestinal mucosa, allowing the entrance of bacteria and toxicants into the bloodstream. Burn damage causes a severe dysbiosis of the gut microbiome in both humans and mice, allowing for similar Gram-negative aerobic bacteria overgrowths. Burn damage also causes mesenteric vasoconstriction, resulting in a hypoxic environment for the intestine. As a result, the intestine is thought to be the “motor” of sepsis [14,15]. Accordingly, one critical goal in the prevention and treatment of sepsis is to protect the lining of the gastrointestinal tract [16,17].

Berberine (Figure 1) is a plant alkaloid found in the roots and bark of a variety of plants, including Coptis chinensis (goldenthread), Berberis aquifolium (Oregon grape), Berberis vulgaris (barberry), Hydrastis canadensis (goldenseal), and Berberis aristata (tree turmeric) [18–20]. Berberine has a diverse range of pharmacological actions, including anticancer [21–23], antidiabetic [24–26], antiobesity, anti-hyperlipidemic [25,27], cardioprotective [25,28], and spatial memory improvement [25,29], immunosuppressive [30] properties, as well as antioxidant and anti-inflammatory activity [31,32]. Berberine has been used to treat intestinal inflammation and infection [33,34]. In the experiments, both oral and injectable delivery methods were employed. Berberine could be absorbed from the GI tract in animals, and its pharmacokinetic characteristics in humans are similar to those shown in animal research. However, the oral bioavailability of berberine appears to be very poor, but there are ways to improve it, such as P-gp inhibitors, enhancers, and lipid microparticle delivery systems [35].

Figure 1. Molecular structure of berberine.

The aim of this review was to describe the potential protective role of berberine on LPS-induced intestine injury and to summarize the different pathways such as those summarized in Figure 2.

Figure 2. An overview of the berberine protective effect in the gut against LPS-induced injury.

2. LPS induces TLR4 signaling

Toll-like receptors (TLRs) have a critical function in innate immunity [36]. TLRs are classified into one of two types: cell surface TLRs and intracellular TLRs. TLR4/MD-2, TLR1/TLR2, and TLR6/TLR2 are cell surface TLR dimers that identify microbial membrane lipids, while TLR3, TLR7, TLR8, and TLR9 are intracellular TLR dimers that identify microbial nucleic acids. The lipopolysaccharide or lipopeptides in the microbial membrane are detected by cell-surface TLRs [10]. TLR4, one of the most studied TLRs, is an LPS receptor [1]. LPS must be delivered to the TLR4 and the MD-2 receptor complex to be activated [10]. LPS stimulates mammalian cells by interacting with several proteins, including the LPS binding protein (LBP), CD14, MD-2, and TLR4. LBP is a soluble shuttle protein that binds to LPS and promotes the interaction of LPS with CD14 [36]. CD14 is a glycosylphosphatidylinositol-anchored protein that transports LPS to the TLR4 and the MD-2 receptor complexes [37]. On the cell surface, MD-2 is non-covalently linked with TLR4 and supports the LPS/TLR4 complex-related cellular response in its response to LPS. As a result, MD-2 serves as a connection between TLR4 and LPS signaling [38].

LPS/TLR4 signaling can be classified as a MyD88-dependent or MyD88-independent pathway. Both can activate the inflammatory pathways regulated by NFκ-B and MAPK [36]. The NFκ-B and MAPK pathways are essential in the production of inflammatory cytokines [39]. TLR4 and MyD88 are upstream mediators of NFκ-B and MAPK [40].

Berberine has been shown to inhibit LPS-induced TLR4 and MyD88 expression, suggesting that berberine may interfere with the LPS-induced TLR4 pathway. Berberine binds to the TLR4/MD-2 receptor with a greater affinity than LPS [41,42]. It has been proposed that berberine may inhibit the generation of pro-inflammatory cytokines by decreasing LPS-induced activation of the TLR4-mediated NFκ-B and MAPK pathways [39,43]. In sepsis, berberine has an important function in organs such as the lung and heart. Guanghui Xu and colleagues reported that berberine given by injection or by inhalation in mice reduced lung injury and enhanced pulmonary morphology by inhibiting LPS-induced TLR4 [44]. Berberine was also found to be effective in reversing myocardial damage in male rats by suppressing the activation of the TLR4 signaling pathway [45].

2.1. Berberine and NF-κB inhibition

NF-κB regulates the transcription of genes involved in the inflammatory response, resulting in increased IL-1β, IL-6, IL-8, and TNF-α [46–49]. IL-1 β can stimulate cell proliferation, differentiation, and death as well as activate the inflammatory response [50]. IL-6 has a range of biological functions in the cytokine network, including the acute-phase response, immune modulation, and inducing lymphocyte differentiation [50,51]. IL-8 causes neutrophil migration and degranulation [52]. TNF-α can affect the infection site by increasing vascular endothelial cell production, stimulating interleukin (IL) and chemokine production, and inducing a large number of leucocytes [53]. Berberine inhibits NF-κB gene expression, which in turn reduces the synthesis of these inflammatory mediators [47]. The inhibitory effect of berberine on TNF-α was shown to be related to its ability to modulate the gut microbiota and reduce endotoxemia in rats [54]. Another in vivo study found that pretreatment with neutral sulfate berberine significantly reduced mortality and tissue damage in the lungs and small intestine of mice exposed to LPS by decreasing plasma TNF-α levels [55].

Under endotoxemic conditions, the NF-κB p65 subunits in the gastrointestinal tract are activated [56]. The activated NF-κB p65 then interacts with the myosin light-chain kinase (MLCK) promoter region, stimulating the production of MLCK mRNA [57,58]. The intestinal tight junctions are regulated by MLCK. MLC phosphorylation by MLCK induces actin-myosin filament contraction, which can lead to changes in the tight junction [59] protein distribution and expression, as well as the functional opening of the TJ barrier. As a result, chemicals that inhibit the NFκB and MLCK, such as berberine, may restore the intestinal TJ barrier in cases of endotoxemia [60,61].

NF-κB inhibitors like IκBa typically sequester NF-κB in the cytoplasm of non-stimulated cells [62]. IκBa is phosphorylated and then is degraded to activate NF-κB [63–65]. In the case of endotoxemia, IκBa, p-IκBa, and p-65 are increased. The expression of IκBa, p-IκBa, and p-65 decreased following exposure to berberine [47]. Zhao and colleagues have suggested that berberine treatment prevents the overactivation of the NF-κB signaling pathway caused by LPS and reduces phosphorylation of IκB and p65 in rumen epithelial cells [39]. These results suggest that berberine inhibits the generation of pro-inflammatory cytokines by inhibiting the activity of the NF-κB pathway [47]. In addition, berberine improved IBS signs by suppressing the TNF-α-NF-κB-MLCK pathway overexpression in rats [66]. According to outcomes of a research in cats, berberine can restore gut microbiota homeostasis and modulate the TLR4/NF-κb pathway, hence reducing inflammatory responses. These results provide insight into the mechanisms of berberine treatment in cats with IBD [67].

2.2. Berberine and MAPK inhibition

Mitogen-activated protein (MAP) kinase is a signaling module found in eukaryotic cells that allow cells to convert extracellular signals such as hormones, cytokines, and growth factors into intracellular responses and thereby control cell growth, differentiation, migration, and inflammation [68]. In some pathologic conditions, the MAPK signaling pathway is disrupted. Activation of MAPK has been confirmed to increase pro-inflammatory cytokine production [69].

ERK1/2, JNK, and p38 MAPK are three well-known MAPK subfamilies [69]. ERK1/2 regulates cell survival, differentiation, and proliferation [70]. JNK and p38MAPK play essential roles in inflammation by inhibiting cell cycle progression and promoting apoptosis. JNK and p38MAPK may perform a crucial function as pro-apoptotic cellular signals in damaged intestinal epithelial cells [71].

Berberine reduced JNK and p38MAPK phosphorylation but not ERK phosphorylation in rumen epithelial cells of Holstein calves indicating that berberine may inhibit JNK and p38MAPK over-activation produced by LPS and prevent the development of downstream inflammatory factors. As a result, berberine’s anti-inflammatory activity on LPS-induced inflammation in rumen epithelial cells might be related to its ability to suppress TLR4-mediated NF-κB and MAPK signaling pathways, and it could be a prospective therapeutic agent for rumen inflammation in subacute ruminal acidosis (SARA) of cows [39]. However, in piglets, berberine decreased both ERK and JNK protein expression, modulated oxidative stress, and preserve intestinal health [72]. According to the study of Zhu and colleagues, Berberine pretreatment may significantly inhibit LPS-induced NF-κB/MAPK signaling pathway in porcine intestinal epithelial cells (IPEC-J2), and inhibit the generation of downstream inflammatory factors. Consequently, berberine is effective in preventing and treating diarrhea caused by Escherichia coli in weaned pigs by decreasing the interaction between the NF-κB/MAPK signaling pathway and associated inflammatory mediators. These findings suggested that berberine might be an effective substance for reducing LPS-induced intestinal inflammation [47].

3. Berberine modulates ApoM/S1P pathway

S1P is a sphingomyelin metabolite that stimulates five G-coupled receptors, including S1P1-5 [73]. S1P has a broad range of biological functions including cell proliferation, apoptosis, immune, and coagulation system control [74]. S1P is also required for vascular integrity and gut-vascular barrier maintenance. The primary carrier of plasma S1P is ApoM, which is found in about 5% of HDL particles [75].

The gut-vascular barrier (GVB) prevents microorganisms from entering the bloodstream and regulates antigen translocation [76]. Increased capillary permeability in the intestinal mucosa contributes to the spread of germs throughout the body [77]. As a result, lowering gut capillary hyperpermeability is important for avoiding gut-derived sepsis [78].

VE (vascular endothelial)-cadherin and beta-catenin are the major adherent junction (AJ) molecules in the gastrointestinal vascular endothelium, while occludin and claudin-12 are the major tight junction [59] molecules [79]. TJ and AJ proteins are both involved in the function of the vascular endothelial barrier. In LPS-stimulated cells, the level of PV1, an endothelial permeability marker, increased, and occludin and β-catenin decreased [78,80]. Thus, endothelial barrier function is disrupted in sepsis, and the vascular wall becomes leaky, resulting in low blood pressure and the potential development of septic shock [81,82].

S1P activates the S1P1 receptor, which raises the trans-monolayer electric resistance in endothelial cells [81,82]. S1P also decreases LPS-induced PV1 expression while increasing occludin and β-catenin levels that are suppressed by LPS [78,80].

LPS, TNF-α, and IL-1 have been shown to suppress ApoM production in the liver [83,84]. Berberine enhanced the hepatic ApoM mRNA and plasma ApoM level during sepsis by inhibiting gluconeogenesis, insulin resistance, and proinflammatory molecule secretion. Berberine has been suggested to protect against GVB damage through modulating the ApoM/S1P pathway [78].

4. Berberine modulates Wnt/beta-catenin signaling pathway

The Wnt genes encode a large family of secreted protein growth factors, cysteine-rich glycoproteins that signal in either a paracrine or autocrine fashion by passing signals into a cell through cell surface receptors. Wnts interact with the 7-span transmembrane protein Frizzled (Fzd) and the single-span low-density lipoprotein receptor-related protein (LRP) and contribute to a variety of biological responses [85]. Wnts activate the release of β-catenin in combination with Fz/LRP [86]. β-Catenin enhances cell–cell adhesion by aggregating at cell–cell contact areas known as adherent junctions [87].

Transepithelial/transendothelial electrical resistance (TEER) is a well-recognized quantitative technique used to evaluate the integrity of the endothelial barrier [88]. In cell culture models of endothelial monolayers, TEER was significantly reduced by LPS. When LPS and berberine were combined, the detrimental effects of LPS were eliminated. He et al. reported that when Wnt/beta-catenin inhibitors were combined with berberine, upregulation of TJ/AJ production was reduced, indicating that berberine stimulation of the Wnt/beta-catenin signaling pathway was involved in the preservation of GVB function. In sepsis, berberine has been proposed to preserve GVB function through modulating the Wnt/beta-catenin signaling pathway [89].

In addition, an in vivo study showed that by physically binding to NF-κb and inhibiting its activation, beta-catenin inhibits NF-κb activity in the same mechanism as IκBα does, indicating that beta-catenin is a negative regulator of NF-κb. As a result, berberine might be beneficial through Wnt/beta-catenin signaling pathway regulation [90].

5. Berberine and COX-2 inhibition

Cyclooxygenase-2 (COX-2) is a pro-inflammatory enzyme that plays a role in the development of intestinal inflammation [33]. In the intestine, basal levels of COX-2 are required for the maintenance of epithelial integrity, proliferation, and homeostasis [91–93]. However, excessively high levels of this enzyme are harmful to the intestinal barrier [91,93,94].

LPS can significantly increase different pro-inflammatory molecules, including iNOS and COX-2, that induce gut mucosal sloughing, while iNOS and COX-2 inhibitors may ameliorate such gut mucosal damage [95,96]. This function of berberine may be beneficial in a variety of pathologic conditions. According to Hsu et al., berberine reduced COX-2 production and induced apoptosis in SW620 human colon cancer cells [97].

5.1. MAPKs and NF-κB induce COX-2 transcription

One of the most important signaling pathways involved in COX-2 gene expression is the mitogen-activated protein kinase (MAPK) pathway [98]. In the enterocyte, COX-2 gene transcription is initiated by p38, inducing and activating ATFs (activating transcription factors) [98]. ATF2 and ATF3 have an important function in the induction of COX-2 gene expression [93,99,100]. LPS injection activated mucosal p38 and ATF2 via enhancing phosphorylation and upregulating ATF2 and ATF3 protein levels in the mucosa. LPS-induced phosphorylation and overproduction of p38 and ATFs were reduced by berberine administration [38]. Berberine may have the potential to reduce LPS-induced COX-2 through suppression of the p38 pathway [101].

NF-kB is an inducible transcription factor that controls the expression of a variety of genes (including cox-2) involved in inflammation [102]. The cox-2 promoter contains two NF-kB-binding sites and NF-kB increases cox-2 expression in response to numerous cytokines [98]. Furthermore, exposure to LPS activates NF-kB, leading in increased COX-2 expression [103]. As a result, berberine might block COX-2 transcription by blocking NF-kB [33].

5.2. IGF-1/IGFBPs signaling and COX-2 overexpression

Overexpression of iNOS and COX-2 has been linked to the inactivation of IGF-1/IGFBPs signaling [104,105]. Insulin-like growth factor 1 (IGF-1) is a polypeptide that regulates immune and inflammation processes [106,107]. IGF-1 enhances enterocyte count, crypt depth, villus height, and surface in the gut, as well as maintaining intestinal barrier performance and inhibiting luminal bacteria and toxicants transfer [108–110]. IGF-1 has a role in the production of claudin-1 and occludin in the gut, and subsequently, the severity of endotoxemia could be reduced by improving the gut tight junctions [111,112]. Ninety-nine percent of IGFs in the plasma is bound to proteins such as IGFBP-3 that control the availability of free IGF-1 [113]. IGFBP-3 is the most common IGFBP in plasma and has the highest affinity to IGF-1. The proper ratio of IGF-1/ IGFBP-3 is necessary for maintaining intestinal homeostasis [114].

LPS significantly inhibits IGF-1 and IGFBP-3 mRNA and their protein expression, leading to disruption of the IGF-1/IGFBP-3 axis. Pretreatment of rats suffering from acute endotoxemia with berberine improved IGF-1/IGFBP3 expression, which was likely due to its inhibition of pro-inflammatory mediators like COX-2 and iNOS [115]. According to Fukuda et al., berberine suppressed COX-2 gene transcription in colon cancer cells at levels greater than 0.3 μM, which might describe the mechanism of the anti-inflammatory and antitumor effect of berberine [116].

5.3. Berberine ameliorates COX-2 expression through the PPARγ pathway

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that are activated by peroxisome proliferators [117]. Three PPAR isotypes have been identified, α, δ, and γ, which play a role in regulating the expression of genes involved in lipid storage and mobilization, glucose metabolism, morphogenesis, and the inflammatory response [118]. PPARα is highly expressed in cells with considerable fatty acid catabolism. PPARδ has the most variable expression pattern, and the amount of expression in different tissues is determined by the level of cell proliferation and differentiation. This isotype has an important role in the skin, intestines, placenta, skeletal muscle, adipose tissue, and brain [119]. PPARγ has been suggested to reduce pro-inflammatory reactions through interaction with PPARγ ligands [120,121]. PPARγ is a negative regulator of inflammation [33]. Intestinal epithelium, macrophages, and vascular endothelial cells all express PPARγ in the gut, which helps preserve gut homeostasis in cases of sepsis [122–125]. The anti-inflammatory mechanism involves some transcription factors, such as NFκB, signal transducer and activator of transcription (STAT), and activator protein 1 (AP-1) or intracellular signaling proteins, including mitogen-activated protein (MAP) kinases [126]. As a result, the elevation of PPARγ expression in the small intestinal mucosa during systemic inflammation is a self-regulating protective mechanism [33]. TLR4 is a powerful PPAR inducing mediator. LPS stimulates the TLR4 signal pathway, which might explain the rise in PPARγ expression in small intestine mucosa [125].

p-PPARγ generation, which is mediated by ERK1/2, is normally low in rats without LPS stimulation; LPS treatment increased the amount of p-PPARγ in endotoxemic rats. LPS not only enhanced PPARγ expression but also stimulated PPARγ phosphorylation [33,126,127]. It has been shown that PPARγ phosphorylation reduces its bioactivity. As a result, LPS-induced phosphorylation of PPARγ may impair the PPARγ pathway [33,128,129].

Feng et al. showed that berberine inhibited LPS-induced phosphorylation of PPARγ, demonstrating a potential protective effect of berberine in PPARγ activity. Berberine acts like a PPARγ pathway modulator and reduces intestinal mucosal inflammation [101]. Berberine reduced the inducible COX-2 overproduction via activating the PPARγ pathway but did not affect the constitutive expression of COX-2 [33]. It has been suggested that berberine could have a protective effect on other organs such as the lungs and liver through the PPARγ pathway [130,131].

6. Berberine and ZIP14 expression

Berberine increases the Zrt-Irt-like protein-14 (ZIP14) expression and influences zinc redistribution to help maintain the intestinal barrier in sepsis through the activation of IGF-1 signaling [132]. The ZIP family is involved in regulating the absorption and transfer of zinc into the cytoplasm. ZIP14 plays a key role in gut zinc homeostasis. ZIP14 is found in intestinal epithelial cells [133,134]. One of the most important effects of zinc is to modulate both inflammatory and immunological responses. In sepsis, redistribution causes zinc dyshomeostasis, impaired immunity, and gut barrier dysfunction [83–85]. Berberine has been shown to increase IGF-1 expression in enterocytes [115]. According to an in vitro study in Caco-2 cells treated with LPS, IGF-I increased intracellular zinc concentration. He et al. have hypothesized that berberine might impact zinc redistribution, thus preserving the intestinal mucosal barrier in sepsis by activating IGF-1 signaling, while pretreatment with AG1024, an inhibitor of IGF-1, blocked the effect of berberine. Berberine may also help alleviate hypozincemia by inducing ZIP14 expression, which subsequently influences zinc translocation into the intestinal mucosa, therefore protecting the gut barrier through the activation of the IGF-1 pathway [132].

7. Conclusion and future perspectives

Despite remarkable developments in our understanding of sepsis immunopathology, therapeutic progress has been less impressive. Due to the high mortality rate of sepsis, numerous attempts have been made to develop better therapeutic approaches to treating sepsis. The therapeutic use of natural products is one of several scientific and clinical approaches currently being investigated for the treatment of sepsis.

Berberine has been used in Chinese traditional medicine for centuries. The pharmacological properties of berberine suggest that it could be used to treat various diseases and pathologies, including diabetes, cancers, cardiovascular disease, hyperlipidemia, hypertension, diarrhea, inflammation, and bacterial and viral infections. In addition to the effects of berberine on the GI tract summarized in Table 1, berberine has also been reported to inhibit oxidative stress and to modulate the gut microbiota [54,135]. Despite some clinical trial studies regarding the effects of berberine on diabetes [136], chronic heart failure [137], hyperlipidemia [138], cancer [139], oral diseases [140], and diarrhea [141], berberine needs to be investigated as a possible therapy for GI illnesses in well-designed clinical trials to further define the potential therapeutic function of berberine in the gut and for treating sepsis.

Table 1. Summary of the protective role of berberine in the gut.

Agent	Dose/Route	Experimental model	Finding	Ref
Berberine hydrochloride	100 mg/kg/oral	Rat	↓ LPS-induced COX-2↓ LPS-induced PPARγ overexpression and phosphorylation ↓ LPS-induced p38/ATFs signal activation	[33]
Berberine hydrochloride	25, 50 mg/kg/oral	Rat	Improvement of LPS-downregulated IGF-1 and IGFBP-3 expression Ameliorating LPS-downregulated claudin-1 and occludin expression	[115]
Berberine	50 mg/kg/oral	Caco-2 cells	↑ Claudin-1 and occludin expression in Caco-2 cells ↑ Intracellular zinc content in LPS-treated Caco-2 cells	[132]
Berberine chloride	5, 10, 20 μM	HepG2 cells	↓ Toll-like receptor 4 overproduction gluconeogenesis and insulin resistance	[78]
Berberine hydrochloride	75,150 and 250 μg/ml	IPEC-J2 cells	↓ IL-1, IL-6, TNF-α, IκBa, p-p65, p-IκBa, p38, p-p38 and p-JNK	[47]
Berberine hydrochloride	10, 20 μM	rat intestinal microvascular endothelial cells	↑Claudin-12, VE-cadherin, and beta-catenin ↑ TEER modulating Wnt/beta-catenin pathway	[89]
Berberine	10, 25, 50, 70, 100 µM	Rumen epithelial cells	↓TLR4 and MyD88 expression JNK and p38MAPK phosphorylation ↓ NF-κB and MAPK-mediated inflammatory pathways activation	[39]
Berberine	1, 5, 10 μg/ml	Rat intestinal microvascular endothelial cells	↓ IL-8 level with 5 and 10 μg/ml concentration↓ IL-6 level with 1,5 and 10 μg/ml concentration	[46]
Neutral sulfate berberine	50 mg/kg/oral	Male mice	↓ Tissue damage of the lungs and small intestine↓plasma TNF-α level	[55]
Berberine	100 µM	Rat Intestinal surface epithelial cells	↓ TLR4 and myeloid differentiation primary response protein Myd88 (Myd88)	[43]
Berberine	200 mg/kg/oral	Male mice	Downregulating of the NF-κB and MLCK pathway ↓ Intestinal epithelium TJ disruption	[20]
Berberine	100 mg/kg/oral	Male rat	Repairing the injured intestinal mucosa, alleviating endotoxemia and restoring intestinal permeability	[34]
Berberine-loaded chitosan/fucoidan-taurine nanoparticles	30 μg/mL	Caco-2 cells/RAW264.7 cells	Avoiding redistribution of TJ protein and restoring barrier function↑TEER	[32]
Berberine	30 and 120 mg/kg Intraperitoneal injection	Rat	↓ Tumor necrosis factor-a (TNF-a), interleukin-1b in plasma ↓ TLR4 and NF-κB in ileum ↑ Activities of SOD and GSH-Px	[135]
Berberine	50 mg/kg/oral	Male BALB/c mice	Inhibiting the TLR4-NF-κB pathway ↓ LPS-induced intestinal injury	[41]

Acknowledgments

The authors thank Mashhad University of Medical Sciences for financial support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Mashhad University of Medical Sciences [484].