Keratinocyte growth factor-2 stimulates P-glycoprotein expression and function in intestinal epithelial cells

Isoorientin Alleviates DSS-Treated Acute Colitis in Mice by Regulating Intestinal Epithelial P-Glycoprotein (P-gp) Expression

Isoorientin (ISO) is a naturally occurring flavonoid with diverse functional properties that mitigate the risk of diseases stemming from oxidation, inflammation, and cancer cell proliferation. P-glycoprotein (P-gp) is a vital component of the intestinal epithelium and may play a role in the onset of intestinal inflammatory conditions, such as inflammatory bowel disease (IBD). Recent studies have suggested that short-chain fatty acids (SCFAs) and secondary bile acids (SBAs) produced by the gut microbiota stimulate the increase of P-gp expression, alleviating excessive inflammation and thereby preservation of intestinal homeostasis. ISO has been shown to improve colon health and modulate the gut microbiota. In this study, we aimed to explore whether ISO can modulate the microbes and their metabolites to influence P-gp expression to alleviate IBD. First, the impact of ISO on dextran sulfate sodium (DSS)-treated colitis in mice was investigated. Second, 16S rRNA gene sequencing was conducted. The present study indicated that ISO mitigated the symptoms and pathological damage associated with DSS-treated colitis in mice. Western blot analysis revealed ISO upregulated P-gp in colon tissues, suggesting the critical role of P-gp protein in intestinal epithelial cells. 16S microbial diversity sequencing revealed ISO restored the richness and variety of intestinal microorganisms in colitis-bearing mice and enriched SCFA-producing bacteria, such as Lachnospiraceae_NK4A136_group. The experiments also revealed that the ISO fecal microbiota transplantation (FMT) inoculation of DSS-treated mice had similarly beneficial results. FMT mice showed a reduction in colitis symptoms, which was more pronounced in ISO-FMT than in CON-FMT mice. Meanwhile, ISO-FMT expanded the abundance of beneficial microorganisms, increased the expression of metabolites, such as SCFAs and total SBAs, and significantly upregulated the expression of P-gp protein. In addition, Spearman's correlation analysis demonstrated a positive correlation between the production of SCFAs and SBAs and the expression of P-gp. The present study identified that ISO increases the expression of P-gp in the intestinal epithelium by regulating intestinal microorganisms and their metabolites, which maintains colonic homeostasis, improves the integrity of the colonic epithelium, and alleviates colitis.

Protein Kinases and Cross-talk between Post-translational Modifications in the Regulation of Drug Transporters

Drug transporters are modulators for drug absorption, distribution, and excretion. Key drug transporters including P-glycoprotein and breast cancer resistance protein of the ABC superfamily; organic anion transporting polypeptide 1B1 and 1B3, organic anion transporter 1 and 3, and organic cation transporter 2, as well as multidrug and toxin extrusion 1 and 2 of the SLC superfamily have been recommended by regulatory agencies to be investigated and evaluated in drug-drug interaction (DDI) studies due to their important roles in determining the efficacy, toxicity and DDI of various drugs. Drug transporters are subjected to multiple levels of control and post-translational modifications (PTMs) provide rapid and versatile ways of regulation. Under pathologic and/or pharmacological conditions, PTMs may be altered in the cellular system, leading to functional changes of transporter proteins. Phosphorylation is by far the most actively investigated form of PTMs in the regulation of transporters. Further, studies in recent years also found that protein kinases coordinate with other PTMs for the dynamic control of these membrane proteins. Here we summarized the regulation of major drug transporters by protein kinases and their cross-talking with other PTMs that may generate a complex regulatory network for fine-tuning the function of these important drug processing modulators. SIGNIFICANCE STATEMENT: Kinases regulate drug transporters in versatile manners; Kinase regulation cross-talks with other PTMs, forming a complex network for transporter regulation; Pathological and/or pharmacological conditions may alter PTMs and affect transporter function with different molecular mechanisms.

Acute regulation of apical ABC transporters in the gut. Potential influence on drug bioavailability

The extensive intestinal surface offers an advantage regarding nutrient, ion and water absorptive capacity but also brings along a high exposition to xenobiotics, including drugs of therapeutic use and food contaminants. After absorption of these compounds by the enterocytes, apical ABC transporters play a key role in secreting them back to the intestinal lumen, hence acting as a transcellular barrier. Rapid and reversible modulation of their activity is a subject of increasing interest for pharmacologists. On the one hand, a decrease in transporter activity may result in increased absorption of therapeutic agents given orally. On the other hand, an increase in transporter activity would decrease their absorption and therapeutic efficacy. Although of less relevance, apical ABC transporters also contribute to disposition of drugs systemically administered. This review article summarizes the present knowledge on the mechanisms aimed to rapidly regulate the activity of the main apical ABC transporters of the gut: multidrug resistance protein 1 (MDR1), multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP). Regulation of these mechanisms by drugs, drug delivery systems, drug excipients and nutritional components are particularly considered. This information could provide the basis for controlled regulation of bioavailability of therapeutic agents and at the same time would help to prevent potential drug-drug interactions.

Angiotensin II inhibits P-glycoprotein in intestinal epithelial cells

AIM

P-glycoprotein (Pgp/MDR1) plays a major role in intestinal homeostasis. Decrease in Pgp function and expression has been implicated in the pathogenesis of IBD. However, inhibitory mechanisms involved in the decrease of Pgp in inflammation are not fully understood. Angiotensin II (Ang II), a peptide hormone predominantly expressed in the epithelial cells of the crypt-villus junction of the intestine, has been shown to exert pro-inflammatory effects in the gut. It is increased in IBD patients and animals with experimental colitis. Whether Ang II directly influences Pgp is not known.

METHODS

Pgp activity was measured as verapamil-sensitive 3 H-digoxin flux. Pgp surface expression and exocytosis were measured by cell surface biotinylation studies. Signalling pathways were elucidated by Western blot analysis and pharmacological approaches.

RESULTS

Ang II (10 nM) significantly inhibited Pgp activity at 60 minutes. Ang II-mediated effects on Pgp function were receptor-mediated as the Ang II receptor 1 (ATR1) antagonist, losartan, blocked Pgp inhibition. Ang II effects on Pgp activity appeared to be mediated via PI3 kinase, p38 MAPK and Akt signalling. Ang II-mediated inhibition of Pgp activity was associated with a decrease in the surface membrane expression of Pgp protein via decreased exocytosis and was found to be dependent on the Akt pathway. Short-term treatment of Ang II (2 mg/kg b.wt., 2 hours) to mice also decreased the membrane expression of Pgp protein levels in ileum and colon.

CONCLUSION

Our findings provide novel insights into the role of Ang II and ATR1 in decreasing Pgp expression in intestinal inflammation.

Keratinocyte Growth Factor-2 Is Protective in Oleic Acid-Induced Acute Lung Injury in Rats

Objective

The aim of this study was to examine the role of keratinocyte growth factor-2 (KGF-2) in oleic acid-induced acute lung injury (ALI) in rats.

Methods

 Forty-five healthy adult male Sprague Dawley rats were divided into 3 groups. Rat ALI model was established by injection of 0.01 mL/kg oleic acid into the tail vein. Rats in the control group were injected with the same amount of normal saline (NS). In the ALI + KGF-2 group, 5 mg/kg of KGF-2 was instilled into the airway of rats 72 hours before the model preparation, and the control group and the ALI model group were instilled with the same amount of NS. The lung permeability index (LPI) and lung wet/dry weight (W / D) ratios were measured 8 hours after the model preparation. The permeability of pulmonary microvascular endothelium was evaluated by Evans blue leakage test. Histopathological changes were observed under light microscope and the ALI pathology score (LIS) was calculated. Ultrastructural changes of lung tissue were observed under electron microscope. The apoptosis was detected by TUNEL assay. The expression of Claudin-5, ZO-1, and VE Cadherin in lung tissue was qualitatively and quantitatively analyzed by immunohistochemistry, Western Blot, and qRT-PCR, respectively.

Results

The ALI model group had severe lung injury and obvious pathological changes, including alveolar septal thickening and inflammatory cell infiltration. TUNEL assay showed that the apoptosis of ALI group was significantly increased. The LIS score, lung W/D ratio, LPI, and Evans blue leakage were significantly higher than those in the control group; electron microscopy showed that the alveolar-capillary barrier was severely damaged in the ALI group. Compared with the control group, the expression of Claudin-5, ZO-1, and VE cadherin in the lung tissue of the ALI model group was significantly attenuated. After pretreatment with KGF-2, the degree of lung tissue damage was significantly reduced and the pathological changes were significantly improved. TUNEL assay showed that the apoptosis of ALI group was decreased. Lung W/D ratio, LPI, and Evans blue leakage decreased; electron microscopy showed that the alveolar-capillary barrier of ALI group recovered significantly. Compared with the ALI model group, the expression of Claudin-5, ZO-1, and VE cadherin in the lung tissue of the KGF-2 pretreatment group increased.

Conclusion

The results indicate that KGF-2 may attenuate oleic acid-induced ALI in rats by maintaining the pulmonary microvascular endothelial barrier, which is an effective ALI preventive measure.

P-glycoprotein multidrug transporter in inflammatory bowel diseases: More questions than answers

The gastrointestinal barrier is constantly exposed to numerous environmental substrates that are foreign and potentially harmful. These xenobiotics can cause shifts in the intestinal microbiota composition, affect mucosal immune responses, disturb tissue integrity and impair regeneration. The multidrug transporter ABCB1/MDR1 p-glycoprotein (p-gp) plays a key role at the front line of host defence by efficiently protecting the gastrointestinal barrier from xenobiotic accumulation. This Editorial discusses how altered expression and function of ABCB1/MDR1 p-gp may contribute to the development and persistence of chronic intestinal inflammation in inflammatory bowel diseases (IBD). Recent evidence implies multiple interactions between intestinal microbiota, innate immunity and xenobiotic metabolism via p-gp. While decreased efflux activity may promote disease susceptibility and drug toxicity, increased efflux activity may confer resistance to therapeutic drugs in IBD. Mice deficient in MDR1A develop spontaneously chronic colitis, providing a highly valuable murine IBD model for the study of intestinal epithelial barrier function, immunoregulation, infectious co-triggers and novel therapeutic approaches. Possible associations of human ABCB1 gene polymorphisms with IBD susceptibility have been evaluated, but results are inconsistent. Future studies must focus on further elucidation of the pathophysiological relevance and immunological functions of p-gp and how its ambiguous effects could be therapeutically targeted in IBD.

Lactobacillus acidophilus stimulates intestinal P-glycoprotein expression via a c-Fos/c-Jun-dependent mechanism in intestinal epithelial cells

Our previous studies showed that Lactobacillus acidophilus (LA) culture supernatant (CS) increased P-glycoprotein [Pgp/multidrug resistance 1 (MDR1)] function, expression, and promoter activity in Caco-2 cells. The current studies were designed to elucidate the molecular mechanisms mediating the stimulatory effects of LA CS on Pgp promoter activity. Deletion analysis indicated that the LA CS response element(s) is located in the -172/+428-bp region, and sequence analysis of this region revealed three potential binding sites for c-Fos or c-Jun: proximal activating protein (AP) 1a (-119/-98 bp), distal AP1b (-99/-78 bp), and AP1c (+175/+196 bp). LA CS (24 h) showed an approximately twofold increase in the protein expression of c-Fos and c-Jun in Caco-2 cells. Electrophoretic mobility shift assay showed that LA CS markedly increased the binding of Caco-2 nuclear proteins to AP1a and AP1b, but not AP1c. The DNA-protein complex was completely eliminated by c-Fos antibody, while c-Jun antibody partially eliminated the complex. Chromatin immunoprecipitation analysis also showed that LA CS enhanced the association of c-Fos and c-Jun (by ∼4- and 1.5-fold, respectively) with endogenous Pgp promoter in Caco-2 cells (p-172/+1). Interestingly, overexpression of c-Fos or c-Jun activated Pgp promoter by nearly twofold each. This increase was further enhanced (∼14-fold) when c-Fos and c-Jun were simultaneously overexpressed, suggesting that the presence of one of these transcription factors potentiates the effect of the other. These studies, for the first time, provide evidence for the involvement of c-Fos/c-Jun in stimulation of Pgp gene expression by LA CS in the human intestine.

Fibroblast growth factors stimulate hair growth through β-catenin and Shh expression in C57BL/6 mice

Growth factors are involved in the regulation of hair morphogenesis and cycle hair growth. The present study sought to investigate the hair growth promoting activities of three approved growth factor drugs, fibroblast growth factor 10 (FGF-10), acidic fibroblast growth factor (FGF-1), and basic fibroblast growth factor (FGF-2), and the mechanism of action. We observed that FGFs promoted hair growth by inducing the anagen phase in telogenic C57BL/6 mice. Specifically, the histomorphometric analysis data indicates that topical application of FGFs induced an earlier anagen phase and prolonged the mature anagen phase, in contrast to the control group. Moreover, the immunohistochemical analysis reveals earlier induction of β-catenin and Sonic hedgehog (Shh) in hair follicles of the FGFs-treated group. These results suggest that FGFs promote hair growth by inducing the anagen phase in resting hair follicles and might be a potential hair growth-promoting agent.