Unveiling adcyap1 as a protective factor linking pain and nerve regeneration through single-cell RNA sequencing of rat dorsal root ganglion neurons.

BACKGROUND: Severe peripheral nerve injury (PNI) often leads to significant movement disorders and intractable pain. Therefore, promoting nerve regeneration while avoiding neuropathic pain is crucial for the clinical treatment of PNI patients. However, established animal models for peripheral neuropathy fail to accurately recapitulate the clinical features of PNI. Additionally, researchers usually investigate neuropathic pain and axonal regeneration separately, leaving the intrinsic relationship between the development of neuropathic pain and nerve regeneration after PNI unclear. To explore the underlying connections between pain and regeneration after PNI and provide potential molecular targets, we performed single-cell RNA sequencing and functional verification in an established rat model, allowing simultaneous study of the neuropathic pain and axonal regeneration after PNI. RESULTS: First, a novel rat model named spared nerve crush (SNC) was created. In this model, two branches of the sciatic nerve were crushed, but the epineurium remained unsevered. This model successfully recapitulated both neuropathic pain and axonal regeneration after PNI, allowing for the study of the intrinsic link between these two crucial biological processes. Dorsal root ganglions (DRGs) from SNC and naïve rats at various time points after SNC were collected for single-cell RNA sequencing (scRNA-seq). After matching all scRNA-seq data to the 7 known DRG types, we discovered that the PEP1 and PEP3 DRG neuron subtypes increased in crushed and uncrushed DRG separately after SNC. Using experimental design scRNA-seq processing (EDSSP), we identified Adcyap1 as a potential gene contributing to both pain and nerve regeneration. Indeed, repeated intrathecal administration of PACAP38 mitigated pain and facilitated axonal regeneration, while Adcyap1 siRNA or PACAP6-38, an antagonist of PAC1R (a receptor of PACAP38) led to both mechanical hyperalgesia and delayed DRG axon regeneration in SNC rats. Moreover, these effects can be reversed by repeated intrathecal administration of PACAP38 in the acute phase but not the late phase after PNI, resulting in alleviated pain and promoted axonal regeneration. CONCLUSIONS: Our study reveals that Adcyap1 is an intrinsic protective factor linking neuropathic pain and axonal regeneration following PNI. This finding provides new potential targets and strategies for early therapeutic intervention of PNI.

KChIP3 N-Terminal 31-50 Fragment Mediates Its Association with TRPV1 and Alleviates Inflammatory Hyperalgesia in Rats.

Potassium voltage-gated channel interacting protein 3 (KChIP3), also termed downstream regulatory element antagonist modulator (DREAM) and calsenilin, is a multifunctional protein belonging to the neuronal calcium sensor (NCS) family. Recent studies revealed the expression of KChIP3 in dorsal root ganglion (DRG) neurons, suggesting the potential role of KChIP3 in peripheral sensory processing. Herein, we show that KChIP3 colocalizes with transient receptor potential ion channel V1 (TRPV1), a critical molecule involved in peripheral sensitization during inflammatory pain. Furthermore, the N-terminal 31-50 fragment of KChIP3 is capable of binding both the intracellular N and C termini of TRPV1, which substantially decreases the surface localization of TRPV1 and the subsequent Ca2+ influx through the channel. Importantly, intrathecal administration of the transmembrane peptide transactivator of transcription (TAT)-31-50 remarkably reduces Ca2+ influx via TRPV1 in DRG neurons and alleviates thermal hyperalgesia and gait alterations in a complete Freund's adjuvant-induced inflammatory pain model in male rats. Moreover, intraplantar injection of TAT-31-50 attenuated the capsaicin-evoked spontaneous pain behavior and thermal hyperalgesia, which further strengthened the regulatory role of TAT-31-50 on TRPV1 channel. In addition, TAT-31-50 could also alleviate inflammatory thermal hyperalgesia in kcnip3-/- rats generated in our study, suggesting that the analgesic effect mediated by TAT-31-50 is independent of endogenous KChIP3. Our study reveals a novel peripheral mechanism for the analgesic function of KChIP3 and provides a potential analgesic agent, TAT-31-50, for the treatment of inflammatory pain.SIGNIFICANCE STATEMENT Inflammatory pain arising from inflamed or injured tissues significantly compromises the quality of life in patients. This study aims to elucidate the role of peripheral potassium channel interacting protein 3 (KChIP3) in inflammatory pain. Direct interaction of the KChIP3 N-terminal 31-50 fragment with transient receptor potential ion channel V1 (TRPV1) was demonstrated. The KChIP3-TRPV1 interaction reduces the surface localization of TRPV1 and thus alleviates heat hyperalgesia and gait alterations induced by peripheral inflammation. Furthermore, the transmembrane transactivator of transcription (TAT)-31-50 peptide showed analgesic effects on inflammatory hyperalgesia independently of endogenous KChIP3. This work reveals a novel mechanism of peripheral KChIP3 in inflammatory hyperalgesia that is distinct from its classical role as a transcriptional repressor in pain modulation.

PKD1 Promotes Functional Synapse Formation Coordinated with N-Cadherin in Hippocampus.

Functional synapse formation is critical for the wiring of neural circuits in the developing brain. The cell adhesion molecule N-cadherin plays important roles in target recognition and synaptogenesis. However, the molecular mechanisms that regulate the localization of N-cadherin and the subsequent effects remain poorly understood. Here, we show that protein kinase D1 (PKD1) directly binds to N-cadherin at amino acid residues 836-871 and phosphorylates it at Ser 869, 871, and 872, thereby increasing the surface localization of N-cadherin and promoting functional synapse formation in primary cultured hippocampal neurons obtained from embryonic day 18 rat embryos of either sex. Intriguingly, neuronal activity enhances the interactions between N-cadherin and PKD1, which are critical for the activity-dependent growth of dendritic spines. Accordingly, either disruption the binding between N-cadherin and PKD1 or preventing the phosphorylation of N-cadherin by PKD1 in the hippocampal CA1 region of male rat leads to the reduction in synapse number and impairment of LTP. Together, this study demonstrates a novel mechanism of PKD1 regulating the surface localization of N-cadherin and suggests that the PKD1-N-cadherin interaction is critical for synapse formation and function.SIGNIFICANCE STATEMENT Defects in synapse formation and function lead to various neurological diseases, although the mechanisms underlying the regulation of synapse development are far from clear. Our results suggest that protein kinase D1 (PKD1) functions upstream of N-cadherin, a classical synaptic adhesion molecule, to promote functional synapse formation. Notably, we identified a crucial binding fragment to PKD1 at C terminus of N-cadherin, and this fragment also contains PKD1 phosphorylation sites. Through this interaction, PKD1 enhances the stability of N-cadherin on cell membrane and promotes synapse morphogenesis and synaptic plasticity in an activity-dependent manner. Our study reveals the role of PKD1 and the potential downstream mechanism in synapse development, and contributes to the research for neurodevelopment and the therapy for neurological diseases.

Probiotics in clostridium difficile Infection.

Clostridium difficile infection (CDI) is one of the most prevalent nosocomial infections. A dramatic increase in the incidence and severity of CDI has been noted in the past decade. Current recommendations suggest metronidazole as first-line therapy in mild to moderately severe CDI and oral vancomycin in individuals with severe CDI, or when metronidazole fails or is contradicted. Alterations of the colonic microbiota, usually caused by antimicrobial therapy, seem to play a critical role in CDI pathogenesis. Probiotics are live microorganisms that confer a health benefit to the host, and have been used in CDI. Although a wide variety of probiotics have been studied, the exact role of probiotics in preventing and treating CDI is not clear. In this study, we reviewed the current literature and recommendations on the most commonly studied protiotic agents (Saccharomyces boulardii, Lactobacillus species, and probiotic mixtures) used to prevent or treat CDI. Lactobacillus-containing probiotic mixtures and S. boulardii may be effective in the prevention of CDI in high-risk antibiotic recipients but this finding is based on small, individual studies, and further, larger, well-controlled studies are needed to confirm preliminary positive findings and to better delineate the efficacy of probiotics in CDI prevention or treatment.

Gait Assessment of Pain and Analgesics: Comparison of the DigiGait™ and CatWalk™ Gait Imaging Systems.

Investigation of pain requires measurements of nociceptive sensitivity and other pain-related behaviors. Recent studies have indicated the superiority of gait analysis over traditional evaluations (e.g., skin sensitivity and sciatic function index [SFI]) in detecting subtle improvements and deteriorations in animal models. Here, pain-related gait parameters, whose criteria include (1) alteration in pain models, (2) correlation with nociceptive threshold, and (3) normalization by analgesics, were identified in representative models of neuropathic pain (spared nerve injury: coordination data) and inflammatory pain (intraplantar complete Freund's adjuvant: both coordination and intensity data) in the DigiGait™ and CatWalk™ systems. DigiGait™ had advantages in fixed speed (controlled by treadmill) and dynamic SFI, while CatWalk™ excelled in intrinsic velocity, intensity data, and high-quality 3D images. Insights into the applicability of each system may provide guidance for selecting the appropriate gait imaging system for different animal models and optimization for future pain research.

gp96 is a human colonocyte plasma membrane binding protein for Clostridium difficile toxin A.

Clostridium difficile toxin A (TxA), a key mediator of antibiotic-associated colitis, requires binding to a cell surface receptor prior to internalization. Our aim was to identify novel plasma membrane TxA binding proteins on human colonocytes. TxA was coupled with biotin and cross-linked to the surface of HT29 human colonic epithelial cells. The main colonocyte binding protein for TxA was identified as glycoprotein 96 (gp96) by coimmunoprecipitation and mass spectrum analysis. gp96 is a member of the heat shock protein family, which is expressed on human colonocyte apical membranes as well as in the cytoplasm. TxA binding to gp96 was confirmed by fluorescence immunostaining and in vitro coimmunoprecipitation. Following TxA binding, the TxA-gp96 complex was translocated from the cell membrane to the cytoplasm. Pretreatment with gp96 antibody decreased TxA binding to colonocytes and inhibited TxA-induced cell rounding. Small interfering RNA directed against gp96 reduced gp96 expression and cytotoxicity in colonocytes. TxA-induced inflammatory signaling via p38 and apoptosis as measured by activation of BAK (Bcl-2 homologous antagonist/killer) and DNA fragmentation were decreased in gp96-deficient B cells. We conclude that human colonocyte gp96 serves as a plasma membrane binding protein that enhances cellular entry of TxA, participates in cellular signaling events in the inflammatory cascade, and facilitates cytotoxicity.

Inhibition of YAP reverses primary resistance to EGFR inhibitors in colorectal cancer cells.

Mutant KRAS and BRAF are associated with primary EGFR inhibitor resistance in colorectal cancer (CRC). However, other biomarkers that could predict EGFR inhibitor resistance remain elusive. In the present study, immunoblotting and cell proliferation results revealed that yes­associated protein (YAP), a downstream effector of the Hippo pathway, was positively associated with primary cetuximab resistance in CRC cells. YAP knockdown enhanced the cytotoxicity of cetuximab in CRC cells. Simvastatin, a 3­hydroxy­3­methylglutaryl­coenzyme A (HMG­CoA) reductase inhibitor of the mevalonate pathway that inhibits YAP bioactivity through nuclear translocation and total YAP expression, increased the cytotoxicity of EGFR inhibitors (cetuximab and gefitinib) against CRC cells. The combination of simvastatin and EGFR inhibitors inhibited YAP and EGFR signaling more markedly than each agent alone. Adding back geranylgeranyl pyrophosphate (GGPP), a key product of the mevalonate pathway, reversed the YAP bioactivity inhibition induced by simvastatin and the cell proliferation inhibition induced by the combination of simvastatin and EGFR inhibitors. Collectively, these results revealed that YAP may be useful in identifying cetuximab resistance in CRC and indicated that targeting of both YAP and EGFR signals may present a promising therapeutic approach for CRC.

[Analysis of two single nucleotide polymorphisms in von Hippel-Lindau gene and detection of loss of heterozygosity in Chinese sporadic renal cell carcinoma].

OBJECTIVE: To exam two single nucleotide polymorphism(SNP) in VHL gene and intragenic loss of heterozygosity (LOH) of VHL gene in 79 Chinese sporadic renal cell carcinomas(RCCs), and to analyze the relationships between VHL LOH and clinicopathological parameters. METHODS: The authors extracted tumor and normal tissue DNA and detected two genotypes of intragenic SNP sites, rs779805 in the 5'terminal and rs 1642742 in the 3'terminal of VHL gene by polymerase chain reaction-restriction frament length polymorphism, then analyzed VHL LOH by comparing tumor tissue versus normal tissue in heterozygosities. Subsequently the relationships between VHL LOH and clinicopathological parameters of RCCs were analyzed. RESULTS: The computed heritage parameters of two SNPs, included genotype frequency, allele frequency, heterozygosity, and polymorphism information content. Twenty-nine heterozygosities were detected in 79 RCCs. LOH was found in 41.4%(12/29) of RCCs. No significant relationships between VHL LOH and age, sex, tumor stage, pathological grade were found. CONCLUSION: LOH of VHL gene is an important genetic event in Chinese sporadic renal carcinoma, and the LOH frequency is 41.4%. VHL LOH has no influence on stage and grade of RCC.

[Analysis of biallelic inactivation of the von Hippel-Lindau tumor suppressor gene VHL in patients of renal cell carcinoma patient].

OBJECTIVE: To investigate biallelic inactivation of the von Hippel-Lindau tumor suppressor gene (VHL) in patient of renal cell carcinoma (RCC) patient. METHODS: We extracted tumor and normal DNA from 41 RCC patients. Mutation of VHL gene from tumor tissue was detected from tumor tissue by polymerase chain reaction (PCR) and direct sequencing. Two single nucleotide polymorphism (SNP) sites located in VHL gene were analyzed by PCR restriction fragment length polymorphism, and loss of heterozygosity (LOH) was analyzed for VHL gene by comparing between tumor with normal tissue. RESULTS: Mutation and LOH of VHL gene was found in 51% (21/41) and 42% (8/19) of RCC patients respectively. LOH was highly associated with mutation positive tumors (r = 0.78) and VHL biallelic inactivation was detected in 37% of RCC patients. CONCLUSION: Biallelic inactivation of VHL gene occurs in RCC due to VHL mutation and LOH, and its frequency rate is 37%.

[The expression of hypoxia inducible factor-1,2 alpha in sporadic clear cell renal cell carcinoma and their relationships to the mutations of von Hippel-Lindau gene].

OBJECTIVE: To evaluate the expression of hypoxia inducible factor (HIF)-1alpha, 2alpha in sporadic clear cell renal cell carcinoma and their relationships to the mutations of von Hippel-Lindau (VHL) gene. METHODS: Mutations of VHL gene, expression of HIF-1alpha and 2alpha were detected by polymerase chain reaction (PCR), direct DNA sequencing and immunohistochemistry in 77 cases of Chinese sporadic clear cell renal cell carcinoma (CCRCC). The stage was pT(1)N(0)M(0)in 55 patients (71%), pT(2)N(0)M(0) in 7 patients (9%), pT(3)N(0)M(0) in 14 patients (18%), and pT(4)N(0)M(0) in 1 patient (1%). The classification according to the tumor nuclear grading system showed 15 carcinomas (19%) of tumor nuclear grade 1, 56 (73%) of tumor nuclear grade 2 and 6 (8%) of tumor nuclear grade 3. RESULTS: None of the VHL gene mutations were found in all the normal tissue specimens. VHL gene mutations were detected in 40 (52%) cases of CCRCC. The positive rate of HIF-2alpha (81%) was higher than that of HIF-1alpha (66%) (chi(2) = 23.310, P < 0.01); The positive rate of HIF-1alpha and HIF-2alpha in the cases of mutations (98% and 93% respectively) was higher than that of them in non-mutations (32% and 68% respectively) (chi(2) = 36.386, 7.617, P < 0.01); The correlation between HIF-1alpha and VHL gene mutations was closer than that between HIF-2alpha and VHL gene mutations (partial correlation coefficiency was 4.481 and 2.027 respectively, P < 0.01). The expression of HIF-1alpha and 2alpha in different pathological grade and stage of CCRCC showed no significant difference (P > 0.05). CONCLUSIONS: Our study suggests that VHL gene mutations are frequent in sporadic CCRCC, and the high expression of HIF-1alpha and 2alpha are found in the group of VHL mutations. However, we have not found significant correlation between the expression of HIF-1alpha and 2alpha and pathological grade and stage of CCRCC in our study.

A Multi-Center Prospective Derivation and Validation of a Clinical Prediction Tool for Severe Clostridium difficile Infection.

BACKGROUND AND AIMS: Prediction of severe clinical outcomes in Clostridium difficile infection (CDI) is important to inform management decisions for optimum patient care. Currently, treatment recommendations for CDI vary based on disease severity but validated methods to predict severe disease are lacking. The aim of the study was to derive and validate a clinical prediction tool for severe outcomes in CDI. METHODS: A cohort totaling 638 patients with CDI was prospectively studied at three tertiary care clinical sites (Boston, Dublin and Houston). The clinical prediction rule (CPR) was developed by multivariate logistic regression analysis using the Boston cohort and the performance of this model was then evaluated in the combined Houston and Dublin cohorts. RESULTS: The CPR included the following three binary variables: age ≥ 65 years, peak serum creatinine ≥ 2 mg/dL and peak peripheral blood leukocyte count of ≥ 20,000 cells/µL. The Clostridium difficile severity score (CDSS) correctly classified 76.5% (95% CI: 70.87-81.31) and 72.5% (95% CI: 67.52-76.91) of patients in the derivation and validation cohorts, respectively. In the validation cohort, CDSS scores of 0, 1, 2 or 3 were associated with severe clinical outcomes of CDI in 4.7%, 13.8%, 33.3% and 40.0% of cases respectively. CONCLUSIONS: We prospectively derived and validated a clinical prediction rule for severe CDI that is simple, reliable and accurate and can be used to identify high-risk patients most likely to benefit from measures to prevent complications of CDI.

Deactivation of excitatory neurons in the prelimbic cortex via Cdk5 promotes pain sensation and anxiety.

The medial prefrontal cortex (mPFC) is implicated in processing sensory-discriminative and affective pain. Nonetheless, the underlying mechanisms are poorly understood. Here we demonstrate a role for excitatory neurons in the prelimbic cortex (PL), a sub-region of mPFC, in the regulation of pain sensation and anxiety-like behaviours. Using a chronic inflammatory pain model, we show that lesion of the PL contralateral but not ipsilateral to the inflamed paw attenuates hyperalgesia and anxiety-like behaviours in rats. Optogenetic activation of contralateral PL excitatory neurons exerts analgesic and anxiolytic effects in mice subjected to chronic pain, whereas inhibition is anxiogenic in naive mice. The intrinsic excitability of contralateral PL excitatory neurons is decreased in chronic pain rats; knocking down cyclin-dependent kinase 5 reverses this deactivation and alleviates behavioural impairments. Together, our findings provide novel insights into the role of PL excitatory neurons in the regulation of sensory and affective pain.

[Mutation of von Hippel-Lindau gene and expression of vascular endothelial growth factor in sporadic clear cell renal cell carcinoma and their relationships to angiogenesis].

OBJECTIVE: To evaluate the relationship between the mutation of the von Hippel-Lindau (VHL) gene and expression of vascular endothelial growth factor (VEGF) in sporadic clear cell renal cell carcinoma (CCRCC) and angiogenesis. METHODS: Polymerase chain reaction (PCR) was used to detect the mutation of VHL gene in the specimens of cancerous tissue and normal tissues away from tumor from 77 patients with CCRCC. Immunohistochemistry was used to examine the expression of VEGF. CD34 staining was used to measure the microvascular density (MVD). RESULTS: VHL gene mutations were detected in 40 cases (51.9%). The expression rate of VEGF was 79.2% (61 cases). The positive rate of VEGF in the cases with VHL mutation was 92.5%, significantly higher than that in the cases without VHL mutation (64.9%, P = 0.003). The levels of MVD was higher in the cases with VHL mutation and those with VEGF expression were 760.80/mm2 and 715.95/mm2 respectively, both significantly higher than those in the cases without VHL-mutation and those without VEGF expression (547.03/mm2 and 437.44/mm2 respectively, all P = 0.001). The cases with expression of VEGF were divided into two groups according the presence or absence of VHL gene mutations or not. The MVD of the cases with VEGF expression and VHL mutation was 760.80 mm2, significantly higher than that of the cases with VEGF expression and without VHL mutation (547.03 mm2, P = 0.011). CONCLUSION: The mutation rate of VHL gene is high among the Chinese with sporadic CCRCC. VHL gene mutation increases significantly the VEGF expression, thus, and perhaps via other mechanism too, promoting the angiogenesis in tumor. The high level of MVD of the cases with VHL gene mutation may be related to the high malignant potential of CCRCC.

[Somatic mutations of VHL gene and HIF-1alpha expression in primary renal clear cell carcinomas].

OBJECTIVE: To evaluate the significance of somatic mutations of VHL gene and hypoxia-inducible factor-1alpha (HIF-1alpha) expression in primary renal clear cell carcinoma (RCC). METHODS: Mutation of VHL gene and HIF-1alpha expression were detected by means of PCR, denaturing high-performance liquid chromatography (DHPLC), direct sequencing and immunohistochemistry in 32 samples from primary renal clear cell carcinoma patients. RESULTS: In 32 RCC samples, 17 samples (53.1%) had and 32 samples of adjacent nonmalignant renal tissue had not mutations of VHL gene expression. Twelve RCC samples (70.6%) which had mutations of VHL gene expressed HIF-1alpha, and it had significant difference to 4 RCC (26.7%) samples which didn't have mutations of VHL gene (P < 0.05). CONCLUSION: Mutations of VHL gene may play a significant role in the tumorigenesis of RCC, and HIF-1alpha expression correlates with it.

[Vitamin D receptor gene Bsm I polymorphism and the susceptibility to prostate cancer in northern Chinese Han population].

OBJECTIVES: To investigate Bsm I single nucleotide polymorphism (SNP) of vitamin D receptor gene (VDRG) in low-risk Chinese Han population and its relationship to the susceptibility to prostate cancer (PCa), and to discuss the possible reason for the racial difference of PCa. METHODS: One hundred and three patients with PCa and 106 normal controls, mainly from Northern Chinese Han population, were enrolled in this study. Their blood samples were obtained, all of which were genotyped for Bsm I SNP by denaturing high performance liquid chromatography(DHPLC) methods using case-control study. RESULTS: The distribution of genotype and allele had no significant difference between PCa patients and normal controls (P > 0.05). The frequencies for the bb, Bb and BB genotypes in PCa patients and normal controls were 92.23%/94.34%, 7.77%/5.66%, and 0/0, respectively. The frequencies for B and b allele were 3.88%, 96.12% and 2.91%, 97.09%, respectively. CONCLUSIONS: The results indicate no significant relationship between the VDRG polymorphisms and PCa in Northern Chinese Han population. The distribution of VDRG Bsm I SNP varies in different ethnic populations, which may be one reason for the racial difference of PCa.

Clostridium difficile toxin A-induced colonocyte apoptosis involves p53-dependent p21(WAF1/CIP1) induction via p38 mitogen-activated protein kinase.

BACKGROUND & AIMS: Clostridium difficile toxin A causes marked apoptosis of colonocytes in vivo and in vitro, which contributes to the formation of ulcers and pseudomembranes. We investigated the role of p53-dependent pathways and p38 mitogen-activated protein kinase (p38) in toxin A-induced colonocyte apoptosis. METHODS: The effects of the activation of p53 and p53-dependent pathways including p21(WAF1/CIP1) were assessed in nontransformed human colonic NCM460 epithelial cells exposed to toxin A. Phosphorylation of p53 protein by p38 was measured by in vitro kinase assay, whereas p21 induction by activated p53 was determined by gel shift assays and RNA silencing (small interfering RNA). The relationship between colonocyte apoptosis and p38/p53-dependent pathways was studied in intact mice. RESULTS: Toxin A stimulated p38 and p53 activation and induced cell cycle arrest (G(2)-M) with persistent expression of p21(WAF1/CIP1). Blockage of p38 by SB203580 inhibited p53 phosphorylation and induction of p21(WAF1/CIP1). In intact mice, p38 blockade suppressed toxin A-mediated destruction of intestinal villi, p21(WAF1/CIP1) expression, and enterocyte apoptosis. In addition, toxin A-mediated p21(WAF1/CIP1) and Bak induction, cytochrome c release, and caspase-3 activation were markedly attenuated in p53-silenced colonocytes, despite active p38. Overexpression of p21(WAF1/CIP1) triggered apoptosis and increased toxin A-associated colonocyte apoptosis. CONCLUSIONS: The signaling pathway for colonocyte apoptosis following toxin A exposure involves p38-dependent activation of p53 and subsequent induction of p21(WAF1/CIP1), resulting in cytochrome c release and caspase-3 activation through Bak induction.

Clostridium difficile toxin B activates the EGF receptor and the ERK/MAP kinase pathway in human colonocytes.

BACKGROUND & AIMS: Clostridium difficile toxin B (TxB) mediates acute inflammatory diarrhea characterized by neutrophil infiltration and intestinal mucosal injury. In a xenograft animal model, TxB was shown to induce interleukin (IL)-8 gene expression in human colonic epithelium. However, the precise mechanisms of this TxB response are unknown. The aim of this study was to investigate the TxB-mediated proinflammatory pathway in colonocytes. METHODS: The effect of TxB on epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK) 1/2 signaling pathway and IL-8 gene expression was assessed in nontransformed human colonic epithelial NCM460 cells. TxB regulation of EGFR-ERK1/2 signaling pathways was determined using immunoblot analysis, confocal microscopy, and enzyme-linked immunosorbent assay, whereas IL-8 gene expression was measured by luciferase promoter assay. RESULTS: TxB activates EGFR and ERK1/2 phosphorylation with subsequent release of IL-8 from human colonocytes. Pretreatment with either the EGFR tyrosine kinase inhibitor, AG1478, or an EGFR-neutralizing antibody blocked both TxB-induced EGFR and ERK activation. By using neutralizing antibodies against known ligands of EGFR, we found that the activation of EGFR and ERK1/2 phosphorylation was mediated by transforming growth factor-alpha (TGF-alpha). Inhibition of matrix metalloproteinase (MMP) decreased TGF-alpha secretion and TxB-induced EGFR and ERK activation. Inhibition of MMP, EGFR, and ERK activation significantly decreased TxB-induced IL-8 expression. CONCLUSIONS: TxB signals acute proinflammatory responses in colonocytes by transactivation of the EGFR and activation of the ERK/MAP kinase pathway.