Blockade of the renin-angiotensin system improves the early stages of liver regeneration and liver function.

BACKGROUND: Partial hepatectomy is the preferred option for selected patients with colorectal cancer liver metastases (CRCLM). Sufficient liver regeneration (LR) is essential for a successful outcome in these patients. The blockade of the renin-angiotensin system (RAS) reduces the growth of several tumor types. The RAS also acts as a regulator of liver fibrosis and potentially LR. The angiotensin-converting enzyme (ACE) inhibitor, captopril, significantly inhibits the growth of CRCLM, but its effect on LR remains undefined. METHODS: After 70% of partial hepatectomy, mice were randomly assigned to control or captopril-treated groups. LR was measured by liver-to-body weight ratio on days 1, 2, 4, 6, and 8. Hepatocyte proliferation, apoptosis and cell size, hepatic stellate cell (HSC) count, and sinusoidal endothelial cell density were quantified. Matrix metalloproteinase 9 (MMP-9) protein levels, liver injury markers, and RAS messenger RNA levels were also determined. RESULTS: At day 2, captopril increased liver-to-body weight ratio (56.5 ± 1.7 captopril versus 49.3 ± 2.4 control, P = 0.027). This was associated with increased HSC count (65.4 ± 4.8 cells per 100,000 µm(2), 48.7 ± 2.3, P = 0.007) and MMP-9 levels (0.68 ± 0.12 AU, 0.12 ± 0.04, P = 0.014). The messenger RNA levels of angiotensin-converting enzyme (P = 0.045) and angiotensin 1 receptor (P = 0.039) were reduced by captopril at day 2. CONCLUSION: Captopril enhanced early LR. This effect was associated with increased HSC numbers and MMP-9 protein, whereas hepatocyte proliferation was lower than controls. Captopril may provide a beneficial treatment option for the management of patients with CRCLM.

Liver regeneration and tumour stimulation: implications of the renin-angiotensin system.

Liver resection is the most effective treatment for primary liver tumours and metastasis to the liver, and remains the only potentially long-term curative therapy for patients with colorectal cancer (CRC) liver metastases. Nevertheless, there is a significant incidence of tumour recurrence following liver resection. Cellular and molecular changes resulting from resection and the subsequent liver regeneration process may influence the kinetics of tumour growth, contributing to recurrence. Although commonly associated with the systemic homeostasis of blood pressure, fluid and electrolyte, the renin-angiotensin system (RAS) has recently been shown to play a role in regulating cell proliferation, apoptosis and angiogenesis in local organs as well as in malignancies. An electronic search of the English literature on the role of the RAS in liver regeneration and tumourigenesis was performed using PubMed, with additional relevant articles sourced from reference lists. Studies have shown that the blockade of the RAS pathway stimulates liver regeneration and inhibits tumour progression. An understanding of the role of RAS in liver regeneration and tumourigenesis may enable alternative strategies to improve patient outcome and survival after liver resection. This review will discuss the role of the RAS in liver regeneration and in tumour recurrence post-liver resection. The potential of the RAS as a novel therapeutic target for CRC liver metastases patients undergoing liver resection will be outlined.

The effect of hyperbaric oxygen on apoptosis and proliferation in severe acute pancreatitis.

OBJECTIVES: This paper investigates the significance of apoptosis in severe acute pancreatitis (SAP) and the possible modulating effects of hyperbaric oxygen (HBO). METHODS: Wistar rats (250-350 g) were induced with SAP by biliopancreatic infusion of 4% sodium taurocholate. Rats were randomized for HBO treatment. Pancreatic tissue was stained for apoptosis with immunohistochemistry (anti-CASPASE-3 antibody and TUNEL), and histopathology haematoxylin and eosin (H&E). Acini were stained for proliferation with an anti-KI67 antibody. ImageProPlus was used to quantify apoptosis and proliferation in acinar cells. Statistical analysis was performed with two-independent-sample t-test or non-parametric Mann-Whitney test. RESULTS: In normal acini there is a low rate of apoptosis (0.165 +/- 0.157%, 0.181 +/- 0.168%, 0.130 +/- 0.298% in CASPASE-3, H&E and TUNEL, respectively) and proliferation (0.951 +/- 0.926%) (mean +/- standard deviation [SD]). When compared with normal, apoptosis (CASPASE-3: 1.28 +/- 1.12%, P= 0.008; 2.40 +/- 3.04%, P= 0.101; 1.23 +/- 0.87%, P= 0.091; H&E: 0.47 +/- 0.36%, P= 0.051; 0.69 +/- 0.63%, P= 0.001; 0.68 +/- 0.28%, P= 0; TUNEL: 1.08 +/- 1.42%, P= 0; 1.96 +/- 1.87%, P= 0; 2.36 +/- 2.26%, P= 0) and proliferation (1.96 +/- 1.89%, P= 0.187; 1.73 +/- 1.76%, P= 0.165; 1.36 +/- 1.40%, P= 0.571) were increased on days 1, 2 and 3 post-induction, respectively. In comparison with the untreated controls, HBO increased apoptosis on day 1 (CASPASE-3: 3.11 +/- 1.97%, P= 0.04; H&E: 0.97 +/- 0.76%, P= 0.005) and day 2 (TUNEL: 3.61 +/- 3.05%, P= 0.034). Treatment with HBO increased proliferation (3.04 +/- 3.14%, P= 0.519; 7.33 +/- 7.55%, P= 0.153) on days 2 and 3, respectively, compared with the untreated controls. CONCLUSIONS: During SAP, acini apoptosis and proliferation were increased. Hyperbaric oxygen therapy may improve the condition of SAP by promoting apoptosis and proliferation.

Tight Junction Protein Claudin-2 Promotes Self-Renewal of Human Colorectal Cancer Stem-like Cells.

Posttreatment recurrence of colorectal cancer, the third most lethal cancer worldwide, is often driven by a subpopulation of cancer stem cells (CSC). The tight junction (TJ) protein claudin-2 is overexpressed in human colorectal cancer, where it enhances cell proliferation, colony formation, and chemoresistance in vitro While several of these biological processes are features of the CSC phenotype, a role for claudin-2 in the regulation of these has not been identified. Here, we report that elevated claudin-2 expression in stage II/III colorectal tumors is associated with poor recurrence-free survival following 5-fluorouracil-based chemotherapy, an outcome in which CSCs play an instrumental role. In patient-derived organoids, primary cells, and cell lines, claudin-2 promoted colorectal cancer self-renewal in vitro and in multiple mouse xenograft models. Claudin-2 enhanced self-renewal of ALDHHigh CSCs and increased their proportion in colorectal cancer cell populations, limiting their differentiation and promoting the phenotypic transition of non-CSCs toward the ALDHHigh phenotype. Next-generation sequencing in ALDHHigh cells revealed that claudin-2 regulated expression of nine miRNAs known to control stem cell signaling. Among these, miR-222-3p was instrumental for the regulation of self-renewal by claudin-2, and enhancement of this self-renewal required activation of YAP, most likely upstream from miR-222-3p. Taken together, our results indicate that overexpression of claudin-2 promotes self-renewal within colorectal cancer stem-like cells, suggesting a potential role for this protein as a therapeutic target in colorectal cancer.Significance: Claudin-2-mediated regulation of YAP activity and miR-222-3p expression drives CSC renewal in colorectal cancer, making it a potential target for therapy. Cancer Res; 78(11); 2925-38. ©2018 AACR.

Blockade of the renin-angiotensin system inhibits growth of colorectal cancer liver metastases in the regenerating liver.

Partial hepatectomy (PH), the preferred option for selected patients with colorectal cancer liver metastases (CRCLM), is associated with 40-80% tumor recurrence rates. Renin-angiotensin system (RAS) blockade inhibits tumor growth and has been suggested to improve liver regeneration. We documented the effect of RAS blockade on tumor growth and liver regeneration in a murine model. CRCLM induction followed by 70% PH was performed on 78 CBA mice. Liver regeneration (days 2, 6) and CRCLM tumor load were measured by liver (and tumor) weights, percentage of CRCLM burden and tumor nodule count (days 16, 21). mRNA expression of the RAS components was characterised. Statistical analysis was performed using 2-independent sample T test or Mann-Whitney test (SPSS). Captopril did not impair liver regeneration. By day 21, Captopril decreased tumor burden (percentage of CRCLM in the liver) (48.7 ± 4.7% control, 24.4 ± 6.2 Captopril; p = 0.008), tumor volume (1046.2 ± 200.2 mm(3), 388.3 ± 150.4; p = 0.02), tumor nodule count per image field (181.1 ± 28.5, 68 ± 17.6; p = 0.005) and tumor angiogenesis (71.8 ± 6.4 vessels/mm(2), 43.1 ± 7.6; p = 0.015) compared to controls. Captopril enhanced tumor apoptosis (1 ± 0.2%, 2.5 ± 0.7; p = 0.028). Liver regeneration and tumor development increased liver ACE levels. Blockade of the RAS effectively retarded CRCLM tumor growth at the late stage of tumor development within the regenerating liver without impeding liver regeneration following PH, via anti-angiogenesis and pro-tumor apoptosis. Captopril may be of therapeutic benefit in patients undergoing PH for CRCLM.

The visceromotor responses to colorectal distension and skin pinch are inhibited by simultaneous jejunal distension.

Noxious stimuli that are applied to different somatic sites interact; often one stimulus diminishes the sensation elicited from another site. By contrast, inhibitory interactions between visceral stimuli are not well documented. We investigated the interaction between the effects of noxious distension of the colorectum and noxious stimuli applied to the jejunum, in the rat. Colorectal distension elicited a visceromotor reflex, which was quantified using electromyographic (EMG) recordings from the external oblique muscle of the upper abdomen. The same motor units were activated when a strong pinch was applied to the flank skin. Distension of the jejunum did not provoke an EMG response at this site, but when it was applied during colorectal distension it blocked the EMG response. Jejunal distension also inhibited the response to noxious skin pinch. The inhibition of the visceromotor response to colorectal distension was prevented by local application of tetrodotoxin to the jejunum, and was markedly reduced when nicardipine was infused into the local jejunal circulation. Chronic sub-diaphragmatic vagotomy had no effect on the colorectal distension-induced EMG activity or its inhibition by jejunal distension. The nicotinic antagonist hexamethonium suppressed phasic contractile activity in the jejunum, had only a small effect on the inhibition of visceromotor response by jejunal distension. It is concluded that signals that arise from skin pinch and colorectal distension converge in the central nervous system with pathways that are activated by jejunal spinal afferents; the jejunal signals strongly inhibit the abdominal motor activity evoked by noxious stimuli.

Identification of neurons that express 5-hydroxytryptamine4 receptors in intestine.

5-Hydroxytryptamine (5-HT) is an endogenous stimulant of intestinal propulsive reflexes. It exerts its effects partly through 5-HT4 receptors; 5-HT4 receptor agonists that are stimulants of intestinal transit are in clinical use. Both pharmacological and recent immunohistochemical studies indicate that 5-HT4 receptors are present on enteric neurons but the specific neurons that express the receptors have not been determined. In the present work, we describe the characterization of an anti-5-HT4 receptor antiserum that reveals immunoreactivity for enteric neurons and other cell types in the gastrointestinal tract. With this antiserum, 5-HT4 receptor immunoreactivity has been found in the muscularis mucosae of the rat oesophagus, a standard assay tissue for 5-HT4 receptors. It is also present in the muscularis mucosae of the guinea-pig and mouse oesophagus. In guinea-pig small intestine and rat and mouse colon, 5-HT4 receptor immunoreactivity occurs in subpopulations of enteric neurons, including prominent large neurons. Double-staining has shown that these large neurons in the guinea-pig small intestine are also immunoreactive for two markers of intrinsic primary afferent neurons, cytoplasmic NeuN and calbindin. Some muscle motor neurons in the myenteric ganglia are immunoreactive for this receptor, whereas it is rarely expressed by secretomotor neurons. Immunoreactivity also occurs in the interstitial cells of Cajal but is faint in the external muscle. Expression of the protein and mRNA has been confirmed in extracts containing enteric neurons. The observations suggest that one site of action of 5-HT4 receptor agonists is the intrinsic primary afferent neurons.