Berberine Improves Intestinal Motility and Visceral Pain in the Mouse Models Mimicking Diarrhea-Predominant Irritable Bowel Syndrome (IBS-D) Symptoms in an Opioid-Receptor Dependent Manner

Abstract

Background and aims: Berberine and its derivatives display potent analgesic, anti-inflammatory and anticancer activity. Here we aimed at characterizing the mechanism of action of berberine in the gastrointestinal (GI) tract and cortical neurons using animal models and in vitro tests.

Methods: The effect of berberine was characterized in murine models mimicking diarrhea-predominant irritable bowel syndrome (IBS-D) symptoms. Then the opioid antagonists were used to identify the receptors involved. Furthermore, the effect of berberineon opioid receptors expression was established in the mouse intestine and rat fetal cortical neurons.

Results: In mouse models, berberine prolonged GI transit and time to diarrhea in a dose-dependent manner, and significantly reduced visceral pain. In physiological conditions the effects of berberine were mediated by mu- (MOR) and delta- (DOR) opioid receptors; hypermotility, excessive secretion and nociception were reversed by berberine through MOR and DOR-dependent action. We also found that berberine increased the expression of MOR and DOR in the mouse bowel and rat fetal cortical neurons.

Conclusion: Berberine significantly improved IBS-D symptoms in animal models, possibly through mu- and delta- opioid receptors. Berberine may become a new drug candidate for the successful treatment of IBS-D in clinical conditions.

Fig 1. Effect of berberine (BER) alone or in presence of opioid antagonists on whole gut transit time in mice.

Data are mean ± SE (n = 6–10). A: I.p. berberine (0.5, 1, 2 and 5 mg/kg) prolonged the whole gut transit time in a dose-dependent manner. **P < 0.01, ***P < 0.001 vs. control. B: I.p. naloxone (NAL, 1 mg/kg), β-funaltrexamine (β-FNA,1 mg/kg) and naltrindole (NTI, 1 mg/kg), but not nor-binaltorphimine (nor-BNI,10 mg/kg) blocked the effects of berberine(BER, 2 mg/kg, i.p.) on the whole gut transit time. ^* P < 0.05, ^** P < 0.01 and ^*** P < 0.001, vs. control; ^# P < 0.05 and ^## P < 0.01, berberine vs. berberine + antagonists.

Fig 2. Effect of berberine (BER) on diarrhea and gastrointestinal hypermotility in mice.

Data are mean ± SE (n = 6–10). A: I.p. berberine (0.5 and 1 mg/kg) prolonged time to diarrhea in the mouse model induced by oral administration of castor oil. ***P < 0.001, vs. control. B: I.p. opioid antagonists: naloxone (NAL, 1 mg/kg) and β-funaltrexamine (β-FNA,1 mg/kg), but not naltrindole (NTI, 1 mg/kg) or nor-binaltorphimine (nor-BNI,10 mg/kg) blocked the effects of berberine(BER, 0.5 mg/kg, i.p.) in the mouse model of castor oil-induced diarrhea. *P < 0.05, **P < 0.01, ***P < 0.001, vs. control; ^# P < 0.05, berberine + antagonists vs. berberine alone. C: I.p.berberine (0.5 and 1 mg/kg)reduced the number of fecal pellets in the mouse model of hypermotility induced by NE (novel environment)-related stress. ^### P < 0.001, non-treated NE-stressed vs. non-treated control; **P < 0.01, *** P < 0.001, vs. non-treated NE-stressed.

Fig 3. Antinociceptive effect of berberine (BER) in mouse models of pain.

Data are mean ± SE (n = 6–10).A: I.p. berberine (0.5 and 1 mg/kg)reduced the number of pain-related behaviors in the mustard oil (i.c.)-induced model of visceral pain. ***P < 0.001, vs. control. B: I.p. opioid antagonists naloxone (NAL, 1 mg/kg), β-funaltrexamine (β-FNA,1 mg/kg) and naltrindole (NTI, 1 mg/kg), but not nor-binaltorphimine (nor-BNI,10 mg/kg)blocked the effects of berberine(BER, 0.5 mg/kg, i.p.)on the number of pain-related behaviors in the mustard oil model.*P < 0.05; ***P < 0.001, vs. control; ^# P < 0.05; ^## P < 0.01, berberine + antagonists vs. berberine alone. C: I.p. berberine (0.5, 1 and 5 mg/kg)reduced the number of pain-related behaviors in the capsaicin-induced model of visceral pain. **P < 0.01; ***P < 0.001, vs. control. D: I.p. berberine (0.5, 1 and 5 mg/kg)reduced the number of pain-related writhing induced by i.p. administration of acetic acid.**P < 0.01; ***P < 0.001, vs. control.

Fig 4. Effects of berberine (BER) on opioid receptor expression in the mouse ileum and colon.

A: Berberine i.p. (1, 2 and 5 mg/kg) increased MOR mRNA expression in the mouse ileum in a dose-dependent manner, and berberine i.p. (2 and 5 mg/kg) increased MOR expression in the mouse colon. *P<0.05,**P<0.01 and ***P<0.001, vs. ileum control; ^# P<0.05, ^### P<0.001, vs. colon control. B: Berberine i.p. (1, 2 and 5 mg/kg) increased DOR mRNA expression in the mouse ileum in a dose-dependent manner, and berberine i.p. (5 mg/kg) increased MOR expression in the mouse colon. *P<0.05, **P<0.01 and ***P<0.001, vs. ileum control; ^# P<0.05 vs. colon control. C: Berberine i.p. (0.5, 1, 2 and 5 mg/kg) had no effect on KOR mRNA expression in the mouse ileum and colon.

Fig 5. Effects of berberine (BER) on opioid receptors expression of mRNA level in rat fetal cortical neurons.

A: Fetal cortical cells cultured for 7 days expressed MOR (β-tubulin⁺ in red, MOR⁺ in green, DAPI⁺ in blue and merged). B: Berberine (BER, 10^-8mol/L) significantly increased MOR mRNA expression when added 1.0 and 2.0 day before cell collection in 7-day culture (***P<0.001 compared with control). C: Berberine (BER 10^-8mol/L) increased DOR mRNA expression when added1.0day before cell collection in 7-day culture. *P<0.05 compared with control. D: Berberine had no effect on KOR expression in 7 day cortical neuron cultures.