Airway basal stem cells generate distinct subpopulations of PNECs

Pulmonary neuroendocrine cells (PNECs) have crucial roles in airway physiology and immunity by producing bioactive amines and neuropeptides (NPs). A variety of human diseases exhibit PNEC hyperplasia. Given accumulated evidence that PNECs represent a heterogenous population of cells, we investigate how PNECs differ, whether the heterogeneity is similarly present in mouse and human cells, and whether specific disease involves discrete PNECs. Herein, we identify three distinct types of PNECs in human and mouse airways based on single and double positivity for TUBB3 and the established NP markers. We show that the three PNEC types exhibit significant differences in NP expression, homeostatic turnover, and response to injury and disease. We provide evidence that these differences parallel their distinct cell of origin from basal stem cells (BSCs) or other airway epithelial progenitors.

Role of Dopamine and D2 Dopamine Receptor in the Pathogenesis of Inflammatory Bowel Disease

BACKGROUND

VEGF-induced vascular permeability and blood vessels remodeling are key features of inflammatory bowel disease (IBD) pathogenesis. Dopamine through D2 receptor (D2R) inhibits VEGF/VPF-mediated vascular permeability and angiogenesis in tumor models. In this study, we tested the hypothesis that pathogenesis of IBD is characterized by the disturbance of dopaminergic system and D2R activity.

METHODS

IL-10 knockout (KO) mice and rats with iodoacetamide-induced ulcerative colitis (UC) were treated intragastrically with D2R agonists quinpirole (1 mg/100 g) or cabergoline (1 or 5 µg/100 g). Macroscopic, histologic, and clinical features of IBD, colonic vascular permeability, and angiogenesis were examined.

RESULTS

Although colonic D2R protein increased, levels of tyrosine hydroxylase and dopamine transporter DAT decreased in both models of IBD. Treatment with quinpirole decreased the size of colonic lesions in rats with iodoacetamide-induced UC (p < 0.01) and reduced colon wet weight in IL-10 KO mice (p < 0.05). Quinpirole decreased colonic vascular permeability (p < 0.001) via downregulation of c-Src and Akt phosphorylation. Cabergoline (5 µg/100 g) reduced vascular permeability but did not affect angiogenesis and improved signs of iodoacetamide-induced UC in rats (p < 0.05).

CONCLUSIONS

Treatment with D2R agonists decreased the severity of UC in two animal models, in part, by attenuation of enhanced vascular permeability and prevention of excessive vascular leakage. Hence, the impairment dopaminergic system seems to be a feature of IBD pathogenesis.

Novel pharmacologic approaches to the prevention and treatment of ulcerative colitis

Ulcerative colitis (UC) is a chronic, relapsing inflammatory disorder of the colonic mucosa followed by poor quality of healing and recurring lesions. Recent studies demonstrated that the poor healing and chronic inflammation in colon of UC could be the result of microvascular dysfunction and endothelial barrier defect, resulting in sustained tissue hypoperfusion and ischemia in the colon. Long before angiogenesis became a popular research topic, our laboratory was the first to postulate that stimulation of angiogenesis alone might be sufficient to accelerate ulcer healing in the gastrointestinal tract. Our earlier studies demonstrated that therapy with genes or peptides of angiogenic growth factors, e.g., bFGF, PDGF and VEGF significantly accelerated healing of experimental duodenal ulcers (DU), while blockade of these angiogenic factors resulted in impaired healing of DU. However, unlike the angiogenesis in DU, increasing evidences from us and others indicate that angiogenesis plays a pathogenic role in UC, e.g., VEGF induces an abnormal "pathologic" angiogenesis which interferes with UC healing. Recently, another angiogenic factor, placental growth factor (PlGF), has also been suggested to be a marker of pathologic angiogenesis and may play a critical role in pathogenesis of UC. Although inhibition of pathologic angiogenesis by, e.g., anti-VEGF or -PlGF, was demonstrated to be a new approach to attenuate UC development, additional data of our and others showed that stimulating angiogenesis by administration of PDGF or bFGF significantly accelerated healing of UC. Also, activation of Rac1, a small GTPase, markedly improved VEGF-induced neovessel architecture defect and reduced vascular permeability (VP) in an angiogenic model. Thus, it seems that both angiogenic and anti-angiogenic therapies may be used in various stages of UC. More recently, we demonstrated that increased VP in colonic mucosa is an early and essential element in the initiation and progression of UC. The increased VP is initiated by early release of histamine and maintained/aggravated by VEGF, leading to perivascular edema, vascular stasis, hypoxia, inflammatory cell infiltration, and colonic erosions/ulcers. Inhibition of increased VP prevents or reduces development and progression of UC. In this review, we discuss novel pharmacologic approaches to prevent UC, differential actions of angiogenic growth factors in UC pathogenesis and blocking the early increase in VP in UC development, these new findings may provide new insights into the regulation of angiogenesis in UC and may lead to development of VP-related drugs to accelerate the healing of UC.

Colonic schistosomiasis and associated cecal neuroma

Schistosomiasis remains a major health threat in many resource-poor countries and is being seen with increasing frequency in developed countries among immigrants and tourists who have a history of freshwater exposure in endemic areas. We report a case ofa 56-year-old male with no significant past medical history, who presented for a routine screening colonoscopy, which revealed two polyps in the cecum, and multiple petechiae in the rectum. Histologic evaluation showed presence of Schistosoma mansoni eggs. One of the polyps, where eggs were also present, was diagnosed as neuroma/ Schwann cell hamartoma. This is the first reported casewhere colonic schistosomiasis is associatedwith cecal neuroma.

Early endothelial damage and increased colonic vascular permeability in the development of experimental ulcerative colitis in rats and mice

The role of endothelial damage and increased vascular permeability (VP) in the pathogenesis of ulcerative colitis (UC) has not been investigated. We examined using functional, morphologic, and molecular biologic studies whether and to what extent the endothelial barrier dysfunction precedes enhanced epithelial permeability (EP) and the development of mucosal lesions during the early stages of experimental UC. We showed that in rats with iodoacetamide (IA)-induced UC increased colonic VP occurs early (ie, 2.6-fold increase at 15 min, P<0.01) preceding changes in epithelial barrier permeability. EP was unchanged at 15 and 30 min after IA administration and was increased 1.9-fold at 1 h and 6.7-fold at 2 h (both P<0.001) after IA. In the dextran sodium sulfate-induced slowly developing UC, colonic VP was significantly increased in 2 days (P<0.05) and EP only in 4 days (P<0.05). Mucosal endothelial injury led to hypoxia (P<0.05) of colonic surface epithelial cells 30 min after IA administration that was associated with increased expressions of transcription factors hypoxia-inducible factor-1α and early growth response-1. Electron and light microscopy demonstrated areas of colonic mucosa with perivascular edema covered by intact layer of surface epithelial cells in both rat and mouse models of UC. This is the first demonstration in four models of UC that endothelial damage, increased colonic VP, perivascular edema, and epithelial hypoxia precede epithelial barrier dysfunction that is followed by erosions, ulceration, and inflammation in UC.

Angiogenic and anti-angiogenic therapy for gastrointestinal ulcers: new challenges for rational therapeutic predictions and drug design

Gastrointestinal (GI) ulcers are essentially internal wounds that resist normal healing processes. Since their pathogenesis is poorly understood, and the etiologic (e.g., gastric acid, aspirin-like drugs, stress) and aggravating factors (e.g., H. pylori) are not well characterized, the remaining therapeutic option is to accelerate healing. Superficial mucosal lesions, i.e., erosions usually heal by epithelial regeneration and restitution, but when ulcers involve the muscularis propria, smooth muscle cells do not divide/regenerate. These deep lesions are filled by granulation tissue, i.e., angiogenesis followed by proliferation of connective tissue fibroblasts that deposit collagen over which adjacent surviving and dividing epithelial cells migrate to complete the healing. Our laboratory was the first to postulate that stimulation of angiogenesis alone might be sufficient to accelerate ulcer healing in the GI tract. Indeed, daily treatment of rats with bFGF, PDGF or VEGF markedly improved the healing of cysteamine-induced chronic duodenal ulcers, without any reduction in gastric acid secretion. These results were reproduced by a single dose of gene therapy by adenoviral vectors encoding PDGF or VEGF genes. The molar potency of angiogenic growth factors was 2-7 million times better than the antiulcerogenic effect of antisecretory H2 antagonists. Since histologically & pathologically gastroduodenal ulcers look similar to ulcers in the lower GI tract, we also predicted that the healing of experimental ulcerative colitis might be also improved by these angiogenic growth factors. Rectal enemas containing bFGF or PDGF indeed accelerated the healing of chemically induced ulcerative colitis in rats. VEGF, also known as VPF (vascular permeability factor), however, had no effect or slightly aggravated the colonic lesions. Injection of anti-VEGF neutralizing antibodies, however, counteracted the increased vascular permeability in the early stages of experimental ulcerative colitis and subsequently decreased the number of inflammatory cells in colonic ulcers in rats, resulting in significantly improved healing in the lower GI tract lesions. Thus, the three angiogenic growth factors tested exerted beneficial effect on gastroduodenal ulcers, and rectal enemas with bFGF or PDGF also accelerated the healing of experimental ulcerative colitis. Surprisingly, we achieved the latter effect with anti-VEGF antibodies, most likely because of the pro-inflammatory actions of VEGF in the pathogenesis of ulcerative colitis.

Molecular mechanisms of basic fibroblast growth factor effect on healing of ulcerative colitis in rats

We demonstrated previously that basic fibroblast growth factor (bFGF) accelerated the healing of experimental duodenal ulcers, and we now hypothesize that bFGF might also accelerate the healing of experimental ulcerative colitis (UC). We also explored the potential molecular mechanisms involved in the accelerated healing of UC in rats treated with bFGF. The results demonstrated that colonic lesions were significantly reduced by bFGF treatment, whereas neutralization of bFGF aggravated iodoacetamide-induced UC. Protein expression of bFGF was increased during the healing stage of UC. Tumor necrosis factor-α levels and myeloperoxidase activity were significantly decreased in UC rats treated with bFGF, whereas they increased in rats treated with anti-bFGF antibody. Real-time polymerase chain reaction and immunohistochemistry showed decreased levels of p27 in the UC rats compared with the healthy controls, which was reversed by bFGF treatment in a dose-dependent manner. By immunohistochemistry and double labeling of Ki-67 and CD34, prominent positive staining of Ki-67 and CD34 was seen after bFGF treatment, indicating the enhanced proliferation of fibroblasts and epithelial and endothelial cells, i.e., angiogenesis. We conclude that bFGF plays a beneficial role in the healing of UC in rats. The molecular mechanisms of bFGF in UC healing not only involve the expected increased cell proliferation, especially angiogenesis, but also encompass the reduction of inflammatory cytokines and infiltration of inflammatory cells. Thus, bFGF enema may be a new therapeutic option for UC.

New cell therapy using bone marrow-derived stem cells/endothelial progenitor cells to accelerate neovascularization in healing of experimental ulcerative colitis

Inflammatory bowel disease (IBD): ulcerative colitis (UC) and Crohn disease (CD) are characterized by recurrent inflammation and ulceration of intestinal and/or colonic mucosa and an inappropriate and delayed healing. Current therapies with, e.g., anti-TNFα antibody (infliximab) and other anti-inflammatory drugs (e.g., mesalamine) do not induce sustained remission, complete healing or prevent recurrence of UC. Although the pathogenesis of UC is not fully understood, pathologic angiogenesis has been postulated as a critical pathogenic component in UC. Recent studies demonstrated that the poor healing, chronic inflammation in colon of UC could be the result of microvascular dysfunction and endothelial barrier defect, resulting in sustained tissue hypoperfusion and ischemia in the colon. Previously, regeneration of injured endothelium and neovascularization were believed to rely solely on the migration and proliferation of neighboring endothelial cells from existing blood vessels. However, accumulating evidence shows that additional mechanisms may exist, and may be mediated by the circulating pool of bone marrow-derived endothelial progenitor cells (BMD-EPC). Furthermore, stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 have been demonstrated to play an important role in the "homing" of BMD-EPC to injured sites and neovascularization in tissue repair. Recent studies by others and us showed reduced BMD-EPC levels in the circulation of IBD patients and rats with experimental UC. However, the potential therapeutic effect of BMD-EPC on neovascularization and colonic mucosal repair in UC has not been elucidated. In this review, we discussed the possibility that impaired contribution of BMD-EPC (i.e., decreased release of BMD-EPC from bone marrow to circulation and/or blocked/impaired homing of BMD-EPC to colonic lesions) may be a critical component of mechanisms in the incomplete/delayed healing of UC, and may offer a novel form of cell therapy for IBD.

Role of anti-angiogenic factor endostatin in the pathogenesis of experimental ulcerative colitis

AIMS

Vascular endothelial growth factor (VEGF) and pathologic angiogenesis have been demonstrated to play a pathogenic role in the development and progression of inflammatory bowel disease. Thus, we hypothesized that the potent anti-angiogenic factor endostatin might play a beneficial role in experimental ulcerative colitis (UC).

MAIN METHODS

We used three animal models of UC: (1) induced by 6% iodoacetamide (IA) in rats, or (2) by 3% dextran sulfate sodium (DSS) in matrix metalloproteinase-9 (MMP-9) knockout (KO) and wild-type mice, and (3) interleukin-10 (IL-10) KO mice. Groups of MMP-9 KO mice with DSS-induced UC were treated with endostatin or water for 5days.

KEY FINDINGS

We found concomitant upregulation of VEGF, PDGF, MMP-9 and endostatin in both rat and mouse models of UC. A positive correlation between the levels of endostatin or VEGF and the sizes of colonic lesions was seen in IA-induced UC. The levels and activities of MMP-9 were also significantly increased during UC induced by IA and IL-10 KO. Deletion of MMP-9 decreased the levels of endostatin in both water- and DSS-treated MMP-9 KO mice. Treatment with endostatin significantly improved DSS-induced UC in MMP-9 KO mice.

SIGNIFICANCE

1) Concomitantly increased endostatin is a defensive response to the increased VEGF in UC, 2) MMP-9 is a key enzyme to generate endostatin which may modulate the balance between VEGF and endostatin during experimental UC, and 3) endostatin treatment plays a beneficial role in UC. Thus, anti-angiogenesis seems to be a new therapeutic option for UC.