Potential role of bile acids in the pathogenesis of necrotizing enterocolitis.

Necrotizing enterocolitis (NEC) is one of the most common acute gastrointestinal diseases in preterm infants. Recent studies have found that NEC is not only caused by changes in the intestinal environment but also by the failure of multiple systems and organs, including the liver. The accumulation of bile acids (BAs) in the ileum and the disorder of ileal BA transporters are related to the ileum injury of NEC. Inflammatory factors such as tumor necrosis factor (TNF)-α and interleukin (IL)-18 secreted by NEC also play an important role in regulating intrahepatic BA transporters. As an important link connecting the liver and intestinal circulation, the bile acid metabolic pathway plays an important role in the regulation of intestinal microbiota, cell proliferation, and barrier protection. In this review, we focus on how bile acids explore the dynamic changes of bile acid metabolism in necrotizing enterocolitis and the potential therapeutic value of targeting the bile acid signaling pathways.

Assessment of Instant Loss of Elbow Flexion in Children with Untreated Gartland IIA Humeral Supracondylar Fractures-A Simulation Study with Lateral Elbow Radiographs.

OBJECTIVE: The suitability of in situ cast fixation for treating Gartland IIA humeral supracondylar fractures has remained controversial due to concerns regarding loss of elbow flexion. This study aimed to assess the instant loss of elbow flexion after Gartland IIA humeral supracondylar fractures based on the relationship between the anterior marginal line of the humerus and capitellum in the lateral view. METHODS: This simulation study was conducted with normal radiographs using Adobe Photoshop 14.0, followed by verification using clinical cases. Standard lateral views of normal elbows of children were collected from January 2008 to February 2020. Adobe Photoshop was used to simulate Gartland IIA supracondylar fractures with different degrees of angulation in the sagittal plane. A formula was deduced to assess flexion loss, and this method was verified in three cases. The data were grouped by age, and the relationship between elbow flexion loss and age, as well as the angulation of the fracture, was analyzed using a one-way or multivariate ANOVA. RESULTS: There was a flexion loss of 19° (11-30°) when the anterior margin line of the humerus was tangential to the capitellum. This loss increased with age at injury (r = 0.731, P = 0.000). Moreover, the difference in angulation in the sagittal plane also influenced the extent of elbow flexion loss (r = -0.739, P = 0.000). The more horizontal the fracture line in the lateral view, the greater the loss of elbow flexion. CONCLUSION: Instant elbow flexion loss after Gartland IIA humeral supracondylar fractures increases with age at the time of injury and decreases with angulation in the sagittal plane. When the anterior margin of the humerus is tangential to the capitellum, there will be an average loss of 19° in elbow flexion. These findings provide a quantitative reference for clinical decision-making in the treatment of Gartland IIA supracondylar fractures.

Effect of powdered vancomycin on stopping surgical site wound infections in neurosurgery: A meta-analysis.

We performed a meta-analysis to evaluate the effect of powdered vancomycin on stopping surgical site wound infections in neurosurgery. A systematic literature search up to July 2022 was performed and 24 137 subjects with neurosurgery at the baseline of the studies; 10 496 of them were using the powdered vancomycin, and 13 641 were not using the powdered vancomycin as a control. Odds ratio (OR) with 95% confidence intervals (CIs) were calculated to assess the effect of powdered vancomycin on stopping surgical site wound infections in neurosurgery using dichotomous methods with a random or fixed-effect model. The powdered vancomycin had significantly lower surgical site wound infections after spinal surgery (OR, 0.53; 95% CI, 0.41-0.70, P < .001), deep surgical site wound infections after spinal surgery (OR, 0.45; 95% CI, 0.35-0.57, P < .001), superficial surgical site wound infections after spinal surgery (OR, 0.60; 95% CI, 0.43-0.83, P = .002), and surgical site wound infections after cranial surgery (OR, 0.37; 95% CI, 0.22-0.61, P < .001) compared to control in subjects with neurosurgery. The powdered vancomycin had significantly lower surgical site wound infections after spinal surgery, deep surgical site wound infections after spinal surgery, superficial surgical site wound infections after spinal surgery, and surgical site wound infections after cranial surgery compared to control in subjects with neurosurgery. The analysis of outcomes should be done with caution even though the low number of studies with low sample size, 3 out of the 42 studies, in the meta-analysis, and a low number of studies in certain comparisons.

Predictive factors for open reduction of flexion-type supracondylar fracture of humerus in children.

OBJECTIVE: The incidence of open reduction and internal fixation (ORIF) in flexion-type supracondylar humerus fractures (SCHF) in children is significantly higher than that of extension-type fractures. This study aimed to identify risk factors for ORIF in flexion-type SCHF. METHODS: One hundred seventy-one patients with Wilkins type III flexion-type SCHF from January 2012 to December 2021 were retrospectively enrolled in a tertiary paediatric hospital. Patients were divided into ORIF group versus closed reduction and internal fixation (CRIF) group. Then, patients data of age, sex, injury side, obesity, deviation of displacement, fracture level, rotation, nerve injury, and delay from injury to surgery were reviewed. Univariate analysis and multivariate logistic regression were used to identify independent risk factors and odds ratios (OR) of ORIF. RESULTS: Overall, 171 children with type III flexion-type SCHF were analyzed (average aged 7.9 ± 2.8 years). Displacement was lateral in 151 cases, medial in 20. 20 cases had combined ulnar nerve injury. The failed closed reduction rate was 20%. Univariate analysis indicated age, distal fracture fragment rotation, and ulnar nerve injury were significantly associated with ORIF. (P = 0.047, P = 0.009, and P = 0.001, respectively). Multivariate logistic regression analysis showed that distal fracture fragment rotation (OR, 3.3; 95%CI:1.1-9.5; P = 0.028) and ulnar nerve injury (OR, 6.4; 95%CI:2.3-18.3; P = 0.001) were independent risk factors; however, the age was not an independent one (OR, 1.5; 95%CI:0.6-3.5; P = 0.397) for ORIF in the Wilkins type III flexion-type SCHF. CONCLUSION: Distal fracture fragment malrotation on initial x-rays and ulnar nerve injury were significant risk factors for ORIF in Wilkins type III flexion-type SCHF. Surgeons should prepare tourniquets or other open reduction instruments when treating these types of fractures. LEVEL OF EVIDENCE: Level IV.

The Integrity of Cartilage Hinge in Song 2/3 Lateral Humeral Condylar Fractures in Children: A Retrospective Radiological Study in Two Centers.

OBJECTIVE: For pediatric lateral condylar fractures (LCFs) of the humerus, it is often hard to determine the stability of the fracture based on the Song classification, especially for those categorized as Song stages 2 and 3. This study aims to define the characteristics of cartilage injury and assess the stability of LCFs classified as Song stages 2 and 3 on post-traumatic magnetic resonance imaging (MRI). METHODS: This was a retrospective study based on imaging data, conducted with a short follow-up period. From January 2016 to May 2019, data of all patients with Song 2 and Song 3 LCFs treated at two institutions were collected. Based on the inclusion criteria, a total of 62 patients with Song stage 2/3 LCF were included. All radiographs were selected for observation and classification for comparison by two observers, both experienced pediatric orthopedic surgeons. MRIs scans for comparison were analyzed in three consecutive coronal sections and cross-sections. Patients were treated conservatively with casting or surgically with closed reduction and percutaneous pinning (CRPP). RESULTS: Altogether 62 cases between 1.5 to 9 years old were included. Reliability analysis revealed poor, moderate, or good agreement between the two observers (range, 0.149-0.633). Both observers showed moderate or good consistency (range, 0.413-0.611). Among the 62 patients diagnosed with Song stages 2 and 3 fractures on initial radiographs, only two patients (3%) had complete fractures with complete disruption of the cartilage hinge as seen on MRI. The hinge was generally located in the posterior-inferior region of the distal humeral cartilage as indicated on MRI. There was no significant difference between Song stages 2 and 3 with regard to ratio of hinge to total values in any cross-sections, nor was there any significant difference in the completeness of the coronal sections (P > 0.05). Of the 62 patients treated, 50 were managed conservatively with casting and 12 underwent CRPP. Forty-nine of the remaining 60 patients (97%) with incomplete fractures were managed conservatively, while the remaining 11 patients were managed with CRPP. All patients with incomplete fractures showed bone healing and no evidence of lateral condyle displacement on follow-up radiographs. CONCLUSIONS: The Song stage 2 or 3 classification is not entirely accurate and is inadequate at guiding treatment outcomes. The cartilage hinge was most likely located posteroinferiorly within the distal humeral epiphysis. According to our findings, conservative treatment with an effective cast or splint may be sufficient for bone healing in case of incomplete cartilage fractures.

Analysis of the location and trajectory of the Kirschner wires in the fixation of extension-type supracondylar fracture of the humerus by 3D computational simulation.

BACKGROUND: Closed reduction and percutaneous pinning is still a preference for the treatment of supracondylar humerus fractures in children. However, no reports have shown the pin trajectory and the characteristics of the entry point so far. So we established a computational simulation model of the elbow to observe the trajectory of pinning for supracondylar humerus fractures. METHODS: We reconstructed an adult elbow computationally and simulated pin placement through lateral and medial pinning. Pin trajectories were traced after placement and after the addition of the skin profile; the relative entry points of the pins were determined. We used the center of the dorsal olecranon inflection as an anatomic reference for the entry points of lateral pinning. Four quadrants were established based on the center of the dorsal olecranon inflection: upper medial quadrant, upper lateral quadrant, lower medial quadrant, and lower lateral quadrant (LLQ). RESULTS: The maximum angle of pinning through the lateral column was 64° ± 3°. The minimum angles of pinning through the lateral column and middle column were 37° ± 3° and 20° ± 2°, respectively. The range of safe angle pinning through the medial column was between 18° ± 2° and 57° ± 3° to avoid penetration of the olecranon fossa and the cortex of the medial column. The entry points of lateral pinning were within the lateral half of the LLQ, and the lateral one-third of the LLQ contained all entry points of the pins through the lateral column and minor points of the pins through the middle column. The exit points of the medial pinning were within the lateral fringe of the metaphyseal-diaphyseal junction region; entering from the inferior two-thirds of the medial epicondyle could lead to the exit points in the proximal half of the metaphyseal-diaphyseal junction region laterally. DISCUSSION: For lateral pinning, the entry points would be within the lateral half of the LLQ. For the pins through the lateral column, the entry points should be within the lateral one-third of the LLQ. For medial pinning, entering from the inferior two-thirds of the medial epicondyle would lead to a more proximal exit.

Toll-like receptor 4-mediated necroptosis in the development of necrotizing enterocolitis.

BACKGROUND: Dramatic intestinal epithelial cell death leading to barrier dysfunction is one of the mechanism of neonatal necrotizing enterocolitis (NEC), in which Toll-like receptor 4 (TLR4) plays a pivotal role. This study explored the role of necroptosis, a drastic way of cell death in NEC. METHODS: The expression of necroptotic proteins was tested in NEC intestinal tissue and compared with controls. NEC was induced in neonatal wild-type mice and a necroptosis inhibitor was given to investigate whether NEC could be relieved. The general condition, macroscopic scoring, and histological evaluations were performed. The expression of tight junction proteins, inflammatory cytokines, and necroptosis-related proteins was measured, and barrier function was examined. Then, NEC was induced in TLR4-knockout pups to confirm the role of TLR4 in necroptosis. RESULTS: Necroptotic proteins were significantly upregulated in both NEC patient and animal models, together with the expression of TLR4. NEC could be relieved and inflammatory infiltration was decreased by necrostatin-1s. TLR4-knockout mice showed milder tissue degradation and less necroptosis after NEC induction. CONCLUSIONS: Necroptosis is an essential pathological process of NEC. TLR4 may be one stimulator of necroptosis in NEC. Inhibiting the intestinal cell necroptosis might be a useful strategy in the treatment of NEC. IMPACT: Necroptosis is a key pathological process in NEC, which appears to involve TLR4. Anti-necroptosis treatment is a promising strategy that could significantly relieve the symptoms of NEC.

Bridging Myositis Ossificans After Supracondylar Humeral Fracture in a Child: A Case Report.

Background: Myositis ossificans is an uncommon complication of trauma and surgery, defined as ossifying changes in a non-osseous tissue such as muscles. It happens after tissue injury, with or without fractures. When myositis ossificans occurs around a joint, it can cause ankylosis, leading to complete dysfunction of the joint. Though it has been described in most parts of the body, bridging myositis ossificans involving the elbow joint were scarcely reported. Case Presentation: We report a severe case of myositis ossificans after a supracondylar humerus fracture in a 9-year-old child. In this case a palpable painless mass appeared following the fracture and surgical trauma. Ultrasound or X-ray is of significant diagnostic value. The brachialis was completely ossified and formed a bony bridge around the elbow, causing complete ankylosis. The bone mass was surgically removed through a bilateral less-invasive approach with less surgical trauma 9 months after initial presentation. we applied bone wax to the fresh bone wounds to prevent the formation of hematocele. Indomethacin, a non-steroidal anti-inflammatory drug, was administered after the operation to suppress bone proliferation in our case. Our patient had the best possible functional status and no recurrence at 2 years' follow-up. Conclusion: Elbow myositis ossificans in children may mainly affects the brachialis. A bilateral less-invasive approach is sufficient to remove the bone mass with less surgical trauma. This case also provides a new reference for the treatment of myositis ossificans after the elbow injuries.

Intestinal vitamin D receptor signaling ameliorates dextran sulfate sodium-induced colitis by suppressing necroptosis of intestinal epithelial cells.

Vitamin D status is closely related to inflammatory bowel disease (IBD), but the mechanism has not been fully elucidated. This study explored the effect of intestinal vitamin D signaling on necroptosis and the underlying mechanism in colitis. Serum 25(OH)D levels and the expression of necroptotic proteins were examined in patients with IBD. Colitis was induced in an intestinal-specific hVDR transgenic model, and the gross manifestation, histological integrity, and intestinal barrier function were tested. The findings were further confirmed in vitro. Immunoprecipitation and colocalization were performed to investigate the association between the vitamin D receptor and necroptotic proteins. We found that serum 25(OH)D decreased in patients with IBD, while the expression of necroptotic proteins increased. The intestinal hVDR transgenic model could largely ameliorate the structural destruction, restore barrier dysfunction, and suppress necroptosis caused by DSS. This was probably achieved by binding to RIPK1/3 necrosomes, as we observed decreased RIPK1/3 necrosome formation and increased VDR expression in the cytosol. This study demonstrated an inhibitory effect of the intestinal vitamin D signaling pathway on necroptosis in DSS-induced colitis. The vitamin D receptor shifts from the nucleus to the cytosol to impede the formation of RIPK1/3. Our findings may offer some theoretical basis for a novel treatment of IBD in clinical practice.

Anterior approach with mini-bikini incision in open reduction in infants with developmental dysplasia of the hip.

PURPOSE: The anterior and medial approaches in open reduction for developmental dysplasia of the hip (DDH) had been widely used. The former could not directly approach the intra-articular interposition, while the latter had been associated with injury to blood vessel and avascular necrosis (AVN) of the femoral head. Meanwhile, the bikini incision had also been mentioned in some studies. The purpose of this study was to introduce a modified anterior approach through a mini-bikini incision and report its short-term outcomes. METHODS: Data of DDH patients younger than 2 years at the time of surgery who had received this mini-bikini incision between June 2013 and December 2018 were collected. The surgical technique, operation duration, intraoperative blood loss, and length of incision were recorded in detail. In the latest follow up, the objective measurement of the scar and the subjective feeling towards the scar were collected. X-ray and magnetic resonance imaging (MRI) were performed at the last follow-up, and the incidence of residual dysplasia, redislocation, and femoral head AVN was analyzed. RESULTS: Forty-three cases (49 hips) were included with an averaged follow-up of 43 months. The operation duration was 22 min, and the blood loss was 9.8 ml on average. The length of the scar averaged 2.6 cm. The mean University of North Carolina "4P" scar scale (UNC4P) for the scar was 0.92, and no patients complained numbness. Overall, all the parents were satisfied with the cosmetic appearance. The mean acetabular index (AI) was 27.42° ± 6.41° in dislocated hip in the last follow-up. One hip redislocated soon after the operation and was reduced in a closed manner right away. MRI showed improved coverage but still some residual dysplasia that was in accordance with the post-operative recovery nature. Four hips (8%) had signs of AVN in X-ray. CONCLUSION: Open reduction through the anterior approach with the mini-bikini incision was a safe procedure with comparable outcomes to classical approaches. It would be a complementary approach for DDH patients younger than 2 years old who need an open reduction.

WISP-2, an upregulated gene in hip cartilage from the DDH model rats, induces chondrocyte apoptosis through PPARγ in vitro.

Chondrocyte apoptosis plays an important role in the developmental dysplasia of the hip (DDH) development. It has been found that WNT1 inducible signaling pathway protein 2 (WISP-2) and peroxisome proliferator-activated receptor γ (PPARγ) are involved in cell apoptosis. In this study, we performed the straight-leg swaddling DDH rat model and we found that cartilage degradation and chondrocyte apoptosis were remarkably increased in DDH rats in vivo. Moreover, we found that WISP-2 was upregulated in hip acetabular cartilage of DDH rats compared to control rats. Next, the effects of WISP-2 on chondrocyte apoptosis and its possible underlying mechanism were examined in vitro. The lentivirus-mediated gain- and loss-of-function experiments of WISP-2 and peroxisome proliferator-activated receptor γ (PPARγ) for cell viability and apoptosis were performed in primary rat chondrocytes. The results showed that the overexpression of WISP-2 induced chondrocyte apoptosis, and knockdown of WISP-2 could suppress the chondrocyte apoptosis induced by advanced glycation end products (AGE). Additionally, WISP-2 could negatively regulate the expression of PPARγ in chondrocytes. Moreover, the knockdown of PPARγ promoted chondrocyte apoptosis and overexpression of PPARγ abated the increased apoptosis and decreased cell viability of chondrocytes induced by WISP-2. This study demonstrated that WISP-2 might contribute to chondrocyte apoptosis of hip acetabular cartilage through regulating PPARγ expression and activation, which may play an important role in the development of DDH.

Mechanical stability study of three techniques used in the fixation of transverse and oblique metaphyseal-diaphyseal junction fractures of the distal humerus in children: a finite element analysis.

BACKGROUND: Management of distal humerus metaphyseal-diaphyseal junction (MDJ) region fractures can be very challenging mainly because of the higher location and characteristics of the fracture lines. Loss of reduction is relatively higher in MDJ fractures treated with classical supracondylar humerus fractures (SHFs) fixation techniques. METHODS: Three different fracture patterns including transverse, medial oblique and lateral oblique fractures were computationally simulated in the coronal plane in the distal MDJ region of a pediatric humerus and fixated with Kirschner Wires (K-wires), elastic stable intramedullary nails (ESIN), and lateral external fixation system (EF). Stiffness values in flexion, extension, valgus, varus, internal, and external rotations for each fixation technique were calculated. RESULTS: In the transverse fracture model, 3C (1-medial, 2-lateral K-wires) had the best stiffness in flexion, varus, internal, and external rotations, while 3L (3-divergent lateral K-wires) was the most stable in extension and valgus. In the medial oblique fracture model, EF had the best stiffness in flexion, extension, valgus, and varus loadings, while the best stiffness in internal and external rotations was generated by 3MC (2-medial, 1-lateral K-wires). In the lateral oblique fracture model, 3C (1-medial, 2-lateral K-wires) had the best stiffness in flexion and internal and external rotations, while ESIN had the best stiffness in extension and valgus and varus loadings. CONCLUSION: The best stability against translational forces in lateral oblique, medial oblique, and transverse MDJ fractures would be provided by ESIN, EF, and K-wires, respectively. K-wires are however superior to both ESIN and EF in stabilizing all three fracture types against torsional forces, with both 2-crossed and 3-crossed K-wires having comparable stability. Depending on the fracture pattern, a 3-crossed configuration with either 2-divergent lateral and 1-medial K-wires or 2-medial and 1-lateral K-wires may offer the best stability.

MicroRNA-26a/b have protective roles in oral lichen planus.

Oral lichen planus (OLP) is a kind of oral epithelial disorder featured with keratinocyte apoptosis and inflammatory reaction. The pathogenesis of OLP remains an enigma. Herein, we showed that the levels of miR-26a/b were robustly down-regulated in oral mucosal biopsies, serum and saliva in OLP patients compared with healthy control. Moreover, we found the binding sites of vitamin D receptor (VDR) in the promoter regions of miR-26a/b genes and proved that the induction of miR-26a/b was VDR dependent. The reduction of miR-26a/b expression was also detected in the oral epithelium of vitamin D deficient or VDR knockout mice. miR-26a/b inhibitors enhanced apoptosis and Type 1T helper (Th1) cells-related cytokines production in oral keratinocytes, whereas miR-26a/b mimics were protective. Mechanistically, we analyzed miRNA target genes and confirmed that miR-26a/b blocked apoptosis by directly targeting Protein Kinase C δ (PKCδ) which promotes cellular apoptotic processes. Meanwhile, miR-26a/b suppressed Th1-related cytokines secretion through targeting cluster of the differentiation 38 (CD38). In accordant with miR-26a/b decreases, PKCδ and CD38 levels were highly elevated in OLP patients' samples. Taken together, our present investigations suggest that vitamin D/VDR-induced miR-26a/b take protective functions in OLP via both inhibiting apoptosis and impeding inflammatory response in oral keratinocytes.

A two-stage retrospective analysis to determine the effect of entry point on higher exit of proximal pins in lateral pinning of supracondylar humerus fracture in children.

BACKGROUND: Kirschner wire fixation remains to be the mainstream treatment modality in unstable or displaced supracondylar humerus fracture in children, with divergent lateral pins being the most preferred due to their sufficient stability and decreased risk of ulnar nerve injury. However, the entry point at which the proximal lateral pin can be inserted to achieve a more proximal exit and maximum divergence has not been reported. This study retrospectively analyzed the characteristics and factors influencing the entry and exit points of the proximal lateral pins. METHODS: The study was divided into two stages. In stage one, the entry and exit points of the proximal pins of lateral pinning configuration were analyzed from intra-operative radiographs of children treated for extension-type supracondylar humerus fractures. The coronal and sagittal pin angles formed by the proximal pins were also measured. Using the findings of stage one, we intentionally tried to achieve a more proximal exit with the proximal pins in stage two. Comparisons between groups of patients treated by random and intentional pinnings were done statistically. RESULTS: In the first stage, 47 (29.2%) of the 161 proximal pins exited above the metaphyseal-diaphyseal junction (MDJ) region. Of these, 85.1% entered from lateral and posterior to the ossific nucleus of the capitellum (ONC). The pin angles averaged 58.4° and 90.5° in the coronal and sagittal planes respectively. In the second stage, 47 (65.3%) proximal pins in the intended group exited above the MDJ region, while only 32 (36%) in the random group exited above the MDJ region. CONCLUSION: While aiming at the upper border of the distal MDJ during pinning, lateral pins can easily achieve a higher, proximal exit above the MDJ if inserted from lateral and posterior to the ONC and parallel to the humeral shaft in the sagittal plane. Higher exit can also be easily achieved in younger patients and patients fixated with smaller diameter pins.

Gut Epithelial Vitamin D Receptor Regulates Microbiota-Dependent Mucosal Inflammation by Suppressing Intestinal Epithelial Cell Apoptosis.

Recent studies show that colonic vitamin D receptor (VDR) signaling protects the mucosal epithelial barrier and suppresses colonic inflammation, but the underlying molecular mechanism remains to be fully understood. To investigate the implication of colonic VDR downregulation seen in patients with inflammatory bowel disease, we assessed the effect of gut epithelial VDR deletion on colonic inflammatory responses in an experimental colitis model. In a 2,4,6-trinitrobenzenesulfonic acid-induced colitis model, mice carrying VDR deletion in gut epithelial cells [VDRflox/flox (VDRf/f);Villin-Cre or VDRΔIEC] or in colonic epithelial cells (VDRf/f;CDX2-Cre or VDRΔCEC) developed more severe clinical colitis than VDRf/f control mice, characterized by more robust T-helper (TH)1 and TH17 responses, with greater increases in mucosal interferon (IFN)-γ+, interleukin (IL)-17+, and IFN-γ+IL-17+ T cells. Accompanying the severe mucosal inflammation was more profound colonic epithelial cell apoptosis in the mutant mice. Treatment with caspase inhibitor Q-VD-OPh dramatically reduced colitis severity and attenuated TH1 and TH17 responses in VDRΔCEC mice. The blockade of cell apoptosis also prevented the increase in mucosal CD11b+CD103+ dendritic cells (DCs), known to be critical for TH17-cell activation. Moreover, depletion of gut commensal bacteria with antibiotics eliminated the robust TH1 and TH17 responses and CD11b+CD103+ DC induction. Taken together, these observations demonstrate that gut epithelial VDR deletion aggravates epithelial cell apoptosis, resulting in increases in mucosal barrier permeability. Consequently, invading luminal bacteria activate CD11b+CD103+ DCs, which promote mucosal TH1 and TH17 responses. Therefore, gut epithelial VDR signaling controls mucosal inflammation by suppressing epithelial cell apoptosis.

Vitamin D treatment attenuates 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis but not oxazolone-induced colitis.

Crohn's disease (CD) and ulcerative colitis (UC) have different immunological mechanisms, while both of them are potential targets of vitamin D treatment. In this study, we have tried to address the role of vitamin D in CD and UC using two mouse models. Mice of C57B6L were given vitamin D before the induction of colitis. Our results showed that vitamin D attenuated 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis but not oxazolone-induced colitis. Vitamin D could preserve the local histology, alleviate inflammation, suppress apoptosis, maintain tight junction function and decrease permeability. Interestingly, it has more of an effect on local structure preservation and inflammation inhibition in CD than in UC mice. Vitamin D blocked the increase of helper T-cell type 1 (Th1)- and helper T-cell type 17 (Th17)-related cytokines in TNBS-induced colitis. But the increase of helper T-cell type 2 (Th2)- and regulatory T cells (Treg)-related cytokines was augmented at the same time in oxazolone-induced colitis which counteracted each other. Our study helps elucidate the differential protective effects of vitamin D on CD and UC patients, as reported in literature.

Activation of the Renin-Angiotensin System Promotes Colitis Development.

The renin-angiotensin system (RAS) plays pathogenic roles in renal and cardiovascular disorders, but whether it is involved in colitis is unclear. Here we show that RenTgMK mice that overexpress active renin from the liver developed more severe colitis than wild-type controls. More than 50% RenTgMK mice died whereas all wild-type mice recovered. RenTgMK mice exhibited more robust mucosal TH17 and TH1/TH17 responses and more profound colonic epithelial cell apoptosis compared to wild-type controls. Treatment with aliskiren (a renin inhibitor), but not hydralazine (a smooth muscle relaxant), ameliorated colitis in RenTgMK mice, although both drugs normalized blood pressure. Chronic infusion of angiotensin II into wild-type mice mimicked the severe colitic phenotype of RenTgMK mice, and treatment with losartan [an angiotensin type 1 receptor blocker (ARB)] ameliorated colitis in wild-type mice, confirming a colitogenic role for the endogenous RAS. In human biopsies, pro-inflammatory cytokines were suppressed in patients with inflammatory bowel disease who were on ARB therapy compared to patients not receiving ARB therapy. These observations demonstrate that activation of the RAS promotes colitis in a blood pressure independent manner. Angiotensin II appears to drive colonic mucosal inflammation by promoting intestinal epithelial cell apoptosis and mucosal TH17 responses in colitis development.

AT1R blocker losartan attenuates intestinal epithelial cell apoptosis in a mouse model of Crohn's disease.

Angiotensin II, which is the main effector of the renin­angiotensin system, has an important role in intestinal inflammation via the angiotensin II type 1 receptor (AT1R). The present study aimed to investigate the protective effects of the AT1R blocker losartan on 2,4,6-trinitrobenzenesulphonic acid (TNBS)-induced colitis. Losartan was administered to male adult C57BL/6 J mice 2 weeks prior to the induction of colitis, and images of the whole colon were captured to record changes, scored according to a microscopic scoring system, and reverse transcription-quantitative polymerase chain reaction were performed in order to investigate colonic inflammation. In addition, intestinal epithelial barrier permeability was evaluated, and intestinal epithelial cell (IEC) apoptosis was measured using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, and apoptosis-related protein expression levels were detected by western blotting. Losartan was able to attenuate TNBS-induced body weight loss and colonic damage. Furthermore, T helper 1-mediated proinflammatory cytokines were suppressed by losartan, and gut permeability was largely preserved. TUNEL staining revealed reduced IEC apoptosis in the losartan-treated mice. Losartan also increased the B-cell lymphoma 2 (Bcl2)/Bcl-2-associated X protein (Bax) ratio and suppressed caspase-3 induction. These results suggested that the AT1R blocker losartan may attenuate TNBS-induced colitis by inhibiting the apoptosis of IECs. The effects of losartan were partially mediated through increasing the Bcl-2/Bax ratio and subsequently suppressing the induction of the proapoptotic mediator caspase-3.

1,25-Dihydroxyvitamin D Protects Intestinal Epithelial Barrier by Regulating the Myosin Light Chain Kinase Signaling Pathway.

BACKGROUND: The myosin light chain kinase (MLCK) pathway controls intestinal epithelial barrier permeability by regulating the tight junction. 1,25-dihydroxyvitamin D (1,25(OH)2D3)-vitamin D receptor (VDR) signaling protects the epithelial barrier, but the molecular mechanism is incompletely understood. METHODS: MLCK activation and barrier permeability were studied using monolayers of HCT116, Caco-2, and SW480 cells treated with tissue necrosis factor α with or without 1,25(OH)2D3. The MLCK pathway was analyzed in normal and inflamed colonic biopsies from patients with ulcerative colitis. Colonic mucosal barrier permeability and MLCK activation were also investigated using trinitrobenzene sulfonic acid-induced colitis models in vitamin D analog paricalcitol-treated wild-type mice and mice carrying VDR deletion in colonic epithelial cells. RESULTS: Tissue necrosis factor α increased cell monolayer permeability and induced long isoform of MLCK expression and myosin II regulatory light chain (MLC) phosphorylation, and 1,25(OH)2D3 blocked tissue necrosis factor α-induced increases in monolayer permeability and MLCK-MLC pathway activation by a VDR-dependent fashion. 1,25(OH)2D3 directly suppressed long MLCK expression by attenuating NF-κB activation, and chromatin immunoprecipitation assays confirmed that 1,25(OH)2D3 disrupted p65 binding to 3 κB sites in long MLCK gene promoter. In human ulcerative colitis biopsies, VDR reduction was associated with increases in long MLCK expression and MLC phosphorylation. In trinitrobenzene sulfonic acid colitis models, paricalcitol ameliorated colitis, attenuated the increase in mucosal barrier permeability, and inhibited long MLCK induction and MLC phosphorylation. In contrast, mice with colonic epithelial VDR deletion exhibited more robust increases in mucosal barrier permeability and MLCK activation compared with wild-type mice. CONCLUSIONS: These data demonstrate that 1,25(OH)2D3-VDR signaling preserves the mucosal barrier integrity by abrogating MLCK-dependent tight junction dysregulation during colonic inflammation.

Transgenic Expression of Vitamin D Receptor in Gut Epithelial Cells Ameliorates Spontaneous Colitis Caused by Interleukin-10 Deficiency.

BACKGROUND: Vitamin D deficiency is common in patients with inflammatory bowel diseases. The vitamin D receptor (VDR) is a nuclear hormone receptor mediating the activity of vitamin D hormone. Our previous studies showed that intestinal epithelial VDR signaling inhibits colitis by protecting the mucosal epithelial barrier, and this activity is independent of non-epithelial immune VDR actions. Interleukin (IL)-10-deficient mouse is a chronic colitis model that develops colitis due to aberrant immune responses. Here we used IL-10 null (IL-10KO) model to assess the anti-colitic activity of epithelial VDR in the setting of an aberrant immune system. METHODS: We crossed IL-10KO mice with villin promoter-driven human (h) VDR transgenic (Tg) mice to generate IL-10KO mice that carry the hVDR transgene in intestinal epithelial cells (IL-10KO/Tg). IL-10KO and IL-10KO/Tg littermates were studied in parallel and followed for up to 25 weeks. RESULTS: By 25 weeks of age, accumulatively 79 % IL-10KO mice developed prolapse, whereas only 40 % IL-10KO/Tg mice did so (P < 0.001). Compared with IL-10KO mice, IL-10KO/Tg littermates showed markedly reduced mucosal inflammation in both small and large intestines, manifested by attenuation in immune cell infiltration and histological damage and a marked decrease in pro-inflammatory cytokine production. IL-10KO/Tg mice also showed reduced intestinal epithelial cell apoptosis as a result of diminished PUMA induction and caspase 3 activation. CONCLUSION: These observations demonstrate that targeting hVDR expression to intestinal epithelial cells is sufficient to attenuate spontaneous colitis caused by an ill-regulated immune system, confirming a critical role of the epithelial VDR signaling in blocking colitis development.