Efficacy of leflunomide for treatment of refractory inflammatory colorectal polyps in 15 Miniature Dachshunds

Retrospective evaluation of leflunomide as an adjunctive therapy in dogs with non-associative immune-mediated thrombocytopenia: 20 cases (2008-2021)

OBJECTIVE

To describe leflunomide as an adjunctive therapy in the treatment of non-associative immune-mediated thrombocytopenia.

MATERIALS AND METHODS

A retrospective study of dogs with a diagnosis of non-associative immune-mediated thrombocytopenia treated with leflunomide March 2008 to September 2021 was conducted. Data collected included signalment, clinical signs, physical examination findings and diagnostic testing performed. Medications administered, duration of hospital stay, time to platelet concentration >150×109/L and adverse events during leflunomide therapy were recorded. Relapses within a year of diagnosis were reported.

RESULTS

A total of 20 client-owned dogs met inclusion criteria. Nineteen of 20 dogs (95%) achieved a platelet concentration >150×109/L with leflunomide and prednisone combination therapy and four dogs (21.1%) relapsed during treatment or shortly after treatment. Adverse effects included diarrhoea (n=5), mild lymphopenia (n=9) and mild intermittent anaemia (n=1). A single dog developed hepatotoxicity presumed to be secondary to leflunomide therapy that resolved after drug discontinuation. One dog was treated for aspiration pneumonia during treatment. Two dogs were euthanased while receiving leflunomide.

CLINICAL SIGNIFICANCE

Length of hospitalisation, time to platelet recovery, treatment response and relapse rate were comparable with alternative treatment protocols. Most adverse effects did not require leflunomide dose adjustment; however, two dogs died while undergoing leflunomide treatment and there is compelling evidence that one of these dogs experienced fatal infection secondary to immune-suppression. Hepatotoxicity remains a known complication of leflunomide treatment and serial biochemistry testing is recommended.

Leflunomide for the Treatment of Immune-Mediated Uveitis in a Dog

A 5 yr old castrated male bichon frise presented with chronic bilateral uveitis that had previously been controlled with systemic steroid administration for 6 mo, resulting in weight gain, polyuria, and polydipsia. To control the uveitis without systemic side effects, oral cyclosporine was started after discontinuing oral steroid, but discontinued one month later because of severe vomiting. Leflunomide (2 mg/kg q 12 hr) was initiated, and the uveitis symptoms resolved after 2 mo. The dose was tapered according to the remission of clinical signs, with no relapse during the following 13 mo. Leflunomide therapy was then discontinued due to vomiting caused by severe gastroenteritis and pancreatitis, and topical prednisolone monotherapy was continued . At 8 mo after discontinuation of leflunomide, bilateral uveitis recurred, and leflunomide therapy was resumed. However, the patient lost vision due to the progression of clinical signs at 33 mo after commencing leflunomide, and evisceration of the glaucomatous right eye was performed at 43 mo. Histopathologic examination revealed lymphocyte and plasma cell infiltration and melanin-laden macrophages in the uveal tissue, and the patient was diagnosed with immune-mediated uveitis. This case indicated that oral leflunomide may be a viable treatment option for canine idiopathic immune-mediated uveitis.

An inflammatory bowel disease-associated SNP increases local thyroglobulin expression to develop inflammation in miniature dachshunds

Inflammatory colorectal polyp (ICRP) in miniature dachshunds (MDs) is a chronic inflammatory bowel disease (IBD) characterized by granulomatous inflammation that consists of neutrophil infiltration and goblet cell hyperplasia in the colon. Recently, we identified five MD-associated single-nucleotide polymorphisms (SNPs), namely PLG, TCOF1, TG, COL9A2, and COL4A4, by whole-exome sequencing. Here, we investigated whether TG c.4567C>T (p.R1523W) is associated with the ICRP pathology. We found that the frequency of the T/T SNP risk allele was significantly increased in MDs with ICRP. In vitro experiments showed that TG expression in non-immune cells was increased by inducing the IL-6 amplifier with IL-6 and TNF-α. On the other hand, a deficiency of TG suppressed the IL-6 amplifier. Moreover, recombinant TG treatment enhanced the activation of the IL-6 amplifier, suggesting that TG is both a positive regulator and a target of the IL-6 amplifier. We also found that TG expression together with two NF-κB targets, IL6 and CCL2, was increased in colon samples isolated from MDs with the T/T risk allele compared to those with the C/C non-risk allele, but serum TG was not increased. Cumulatively, these results suggest that the T/T SNP is an expression quantitative trait locus (eQTL) of TG mRNA in the colon, and local TG expression triggered by this SNP increases the risk of ICRP in MDs via the IL-6 amplifier. Therefore, TG c.4567C>T is a diagnostic target for ICRP in MDs, and TG-mediated IL-6 amplifier activation in the colon is a possible therapeutic target for ICRP.

Gene expression of leucine-rich alpha-2 glycoprotein in the polypoid lesion of inflammatory colorectal polyps in miniature dachshunds

Inflammatory colorectal polyps (ICRPs) in miniature dachshunds (MDs) are speculated to be a breed-specific inflammatory bowel disease (IBD). Leucine-rich alpha-2 glycoprotein (LRG) has been identified as a novel biomarker of human IBD. The aim of this study was to examine LRG gene expression in the polypoid lesions of ICRPs. Polypoid lesion specimens were collected from 24 MDs with ICRPs. Nonpolypoid colonic mucosa was collected from 18 MDs with ICRPs and 10 controls. The gene expression of LRG, interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and IL-22 was examined. The expression of LRG gene was significantly increased in the polypoid lesions of ICRPs and correlated with that of the four cytokines. In conclusion, the LRG gene was expressed within the polypoid lesions of ICRPs and might be associated with local cytokine expression.

Activities of matrix metalloproteinase-2, matrix metalloproteinase-9, and serine proteases in samples of the colorectal mucosa of Miniature Dachshunds with inflammatory colorectal polyps

OBJECTIVE

To investigate the activities of gelatinases (matrix metalloproteinase [MMP]-2 and MMP-9) and serine proteases in the colorectal mucosa of Miniature Dachshunds (MDs) with inflammatory colorectal polyps (ICRPs).

ANIMALS

15 MDs with ICRPs and 5 dogs with non-ICRP-related large bowel diarrhea (controls).

PROCEDURES

Zymographic methods were used to evaluate the activities of MMP-2, MMP-9, latent forms of MMP-2 and MMP-9 (pro-MMP-2 and pro-MMP-9), and serine proteases in inflamed and noninflamed tissue samples from MDs with ICRPs and in noninflamed tissue samples from control dogs. The associations of serine protease activities with MMP-2 or MMP-9 activity were also analyzed.

RESULTS

Activities of pro-MMP-2 and pro-MMP-9 were detected in most tissue samples, regardless of the tissue type, whereas activities of MMP-2 and MMP-9 were not detected in control tissue samples. In the inflamed tissue samples from MDs with ICRPs, the activities of MMP-2, pro-MMP-9, and MMP-9 were significantly higher than those in the noninflamed tissue samples from those dogs. Serine protease activities were significantly higher in the inflamed and noninflamed tissue samples from MDs with ICRP, compared with findings for control tissue samples. A weak correlation was detected between serine protease activities and MMP-9 activity.

CONCLUSIONS AND CLINICAL RELEVANCE

Study results suggested that gelatinase and serine protease activities are upregulated in the colorectal mucosa of MDs with ICRPs, possibly contributing to the pathogenesis of this disease through the functions of these enzymes in degradation of extracellular matrix and promotion of inflammatory cell migration and inflammatory responses.

Comparison of the efficacy of cyclosporine and leflunomide in treating inflammatory colorectal polyps in miniature dachshunds

Inflammatory colorectal polyps (ICRPs) are frequently observed in miniature dachshunds in Japan and treated by prednisolone and immunosuppressive drugs such as cyclosporine and leflunomide. The purpose of this retrospective study was to compare the treatment efficacy, such as response rate, response interval, recurrence rate, and adverse events between cyclosporine and leflunomide. While the response rates were significantly higher in dogs treated with leflunomide, no significant differences were observed in the response interval or recurrence rate. Two of the 11 dogs treated with leflunomide showed hematological or gastrointestinal adverse events, while no dog treated with cyclosporine showed any adverse events. A case-controlled prospective study to compare the treatment efficacy of leflunomide with that of cyclosporine should be conducted.

Distribution of regulatory T cells in inflammatory colorectal polyps of miniature dachshunds

Inflammatory colorectal polyp (ICRP) is an emerging disease in Miniature Dachshunds (MDs). Animals with this disease exhibit multiple polyps with severe neutrophil infiltration that respond to immunosuppressive therapy. Macrophages in polypoid lesions have been described to play an important role in neutrophil infiltration in the lesion by producing IL-8. In contrast, IL-10, an anti-inflammatory cytokine, was also reported to be upregulated in polypoid lesions, but its significance in the pathogenesis of ICRP has not been clarified. Regulatory T cells (Tregs) are the main source of IL-10 production and contribute to the maintenance of intestinal homeostasis. Therefore, the objective of this research was to compare the distribution of Tregs in polypoid lesions of ICRPs and the association between the distribution and expression of pro- or anti-inflammatory cytokines. Tissue biopsy specimens of polypoid lesions were collected from 28 MDs with ICRP. Those of macroscopically non-polypoid colonic mucosa from 24 MDs with ICRPs and 21 control dogs were further included as controls. Real-time quantitative polymerase chain reaction was used to quantify gene expression of IL-1β, IL-4, IL-6, IL-8, IL-10, IL-17, IL-22, IFN-γ, TNF-α, TGF-β, and forkhead box protein P3 (Foxp3) in each tissue sample. The numbers of Foxp3-positive cells (Tregs) and ionized calcium binding adapter molecule 1 (Iba-1)-positive cells (macrophages) were determined by immunohistochemistry. The gene expression of IL-1β, IL-6, IL-8, TNF-α, IFN-γ, IL-17, IL-10, TGF-β, and Foxp3 was significantly upregulated in polypoid lesions relative to control levels. The numbers of Foxp3-positive Tregs and Iba-1-positive macrophages were significantly increased in polypoid lesions compared to those in the non-polypoid colonic mucosa of MDs with ICRPs and control dogs. The upregulation of IL-10 was moderately correlated with the distribution of Tregs in polypoid lesions from MDs with ICRPs. In addition, the relative upregulation of IL-1β, IL-6, and IL-8 in polypoid lesions, compared to expression in non-polypoid colonic mucosa of MDs with ICRPs, was significantly greater than that of IL-10. These results indicate that increases in Treg numbers and anti-inflammatory cytokines in polypoid lesions comprise reactive changes in response to the inflammation, which warrants further investigation.

ACVIM consensus statement on the treatment of immune-mediated hemolytic anemia in dogs

Immune‐mediated hemolytic anemia (IMHA) causes severe anemia in dogs and is associated with considerable morbidity and mortality. Treatment with various immunosuppressive and antithrombotic drugs has been described anecdotally and in previous studies, but little consensus exists among veterinarians as to the optimal regimen to employ and maintain after diagnosis of the disease. To address this inconsistency and provide evidence‐based guidelines for treatment of IMHA in dogs, we identified and extracted data from studies published in the veterinary literature. We developed a novel tool for evaluation of evidence quality, using it to assess study design, diagnostic criteria, explanation of treatment regimens, and validity of statistical methods. In combination with our clinical experience and comparable guidelines for humans afflicted with autoimmune hemolytic anemia, we used the conclusions of this process to make a set of clinical recommendations regarding treatment of IMHA in dogs, which we refined subsequently by conducting several iterations of Delphi review. Additionally, we considered emerging treatments for IMHA in dogs and highlighted areas deserving of future research. Comments were solicited from several professional bodies to maximize clinical applicability before the recommendations were submitted for publication. The resulting document is intended to provide clinical guidelines for management of IMHA in dogs. These guidelines should be implemented pragmatically, with consideration of animal, owner, and veterinary factors that may vary among cases.

Combination Chlorambucil/Firocoxib or Chlorambucil/Prednisolone Treatment for Inflammatory Colorectal Polyps in Miniature Dachshunds

Inflammatory colorectal polyps (ICRP), which are more commonly recognized in miniature dachshunds, are thought to represent an immune-mediated disease. This retrospective case series describes six miniature dachshunds with refractory ICRP, who were treated with chlorambucil (CLB) combined with firocoxib or prednisolone. Improvement in clinical manifestations was seen in five of the six dogs by the end of the study period; four were treated with CLB/firocoxib and one with CLB/prednisolone. One dog had nonregenerative anemia after 23 mo of treatment with CLB, but whether there was a causative relationship was unclear. No severe adverse events were observed during treatment in the remaining five dogs. CLB in combination with firocoxib or prednisolone appears to be an effective alternative treatment for ICRP in dogs. Further studies are needed to confirm the effectiveness and long-term complications of CLB treatment for ICRP in dogs.

Analysis of fecal short chain fatty acid concentration in miniature dachshunds with inflammatory colorectal polyps

Short chain fatty acids (SCFAs) play an important role in the maintenance of colonic homeostasis, and their depletion has been reported in various gastrointestinal disorders. Inflammatory colorectal polyps (ICRPs) are a recently recognized disease specific to miniature dachshunds (MDs), and fecal dysbiosis with a reduction of SCFA-producing bacteria has been reported with this disease. Therefore, this study was performed based on the hypothesis that a reduced SCFA concentration associates with the development of ICRPs. We recruited 11 ICRP-affected MDs and 25 control MDs. Their fecal SCFA concentrations and bacterial proportions were quantified using high performance liquid chromatography and quantitative real-time PCR, respectively. The feces of ICRP-affected MDs contained lower amounts of propionic acid and lower proportions of Bifidobacterium than the feces of control MDs. Furthermore, fecal proportions of Bifidobacterium, Firmicutes and Lactobacillus exhibited significant positive correlations with fecal concentrations of total SCFAs and/or propionic acid; fecal Escherichia coli proportions correlated negatively with fecal concentrations of total SCFAs, as well as acetic, propionic and butyric acid. This result indicates an association between fecal dysbiosis and fecal SCFA concentrations; these phenomena may contribute to ICRP pathogenesis in MDs. Potential therapeutic targeting of the reduced propionic acid concentration using probiotics, prebiotics or SCFA enemas merits further study.

A Retrospective Study on the Safety and Efficacy of Leflunomide in Dogs

Background

Little clinical information is available concerning the use of leflunomide in dogs with immune‐mediated diseases.

Objectives

To report the safety and efficacy of leflunomide for the treatment of naturally occurring immune‐mediated diseases in dogs.

Animals

Ninety‐two dogs treated with leflunomide for management of suspected immune‐mediated diseases.

Methods

Retrospective medical record review from Jan 1995 to Dec 2014. Data that were extracted from the medical records included signalment, body weight, underlying indication for leflunomide, dosage of leflunomide, treatment duration, concurrent medications, treatment response, and adverse events.

Results

Adverse events that could be related to leflunomide administration included diarrhea (3 of 92, 3.3%), lethargy (2 of 92, 2.2%), unexplained hemorrhage (3 of 92, 3.3%), thrombocytopenia (2 of 31, 6.5%), and increased liver enzyme activities (1 of 16, 6.3%). Significant dose differences between dogs with adverse events (n = 11; median, 2.9 mg/kg/d; range, 1.8–3.6 mg/kg/d) and dogs without adverse events (n = 81; median, 1.6 mg/kg/d; range, 0.8–4.3 mg/kg/d) were found (P < 0.001). Treatment response could be evaluated in 17 dogs. Of these 17 dogs, 12 dogs (70.5%) had an apparent positive response to the use of leflunomide. There was no significant difference (P = 0.22) in dosages between dogs that responded to leflunomide (n = 12; median, 1.9 mg/kg/d; range, 1.0–3.5 mg/kg/d) and those that did not respond (n = 5; median, 1.7 mg/kg/d; range, 1.0–2.0 mg/kg/d).

Conclusions and Clinical Importance

Results suggest that the starting dosage of leflunomide should be 2 mg/kg/d rather than the currently suggested dosage of 3–4 mg/kg/d.

Stimulation of colorectal biopsies from miniature dachshunds with inflammatory colorectal polyps with toll-like receptor ligands: A pilot study

Inflammatory colorectal polyps (ICRPs) in miniature dachshunds (MDs) are a possible novel form of breed-specific canine inflammatory bowel disease (IBD). In this pilot study, we investigated the effects of different Toll like receptor (TLR2, TLR4, TLR5 and TLR9) ligands on pro-inflammatory cytokines (IL-1β, IL-6, IL-8 and TNF-α) gene expression in ex vivo-cultured colorectal samples from four MDs with ICRPs and four healthy MDs. At baseline, no significant difference in the mRNA expression levels of TLRs and pro-inflammatory cytokines was observed between cases and control MDs. After 4-h incubation, the relative ratios of TNF-α mRNA expression in the TLR2- or TLR4-stimulated colorectal samples, and IL-1β mRNA expression in the TLR9-stimulated colorectal samples form cases showed higher tendency compared with healthy MDs (P<0.05), although statistically not significant. The results of this pilot study using small number of cases indicated that reactivity against TLR2, TLR4 or TLR9 ligand in the production of pro-inflammatory cytokines might be enhanced in the colorectal mucosa of ICRPs. Further research is needed to perform the functional analysis of TLRs in the sole cell population using intestinal epithelial primary culture and the mononuclear cells isolated from colonic mucosa.

Expression of apical junction complex proteins in colorectal mucosa of miniature dachshunds with inflammatory colorectal polyps

We examine the expression of tight junction and adherence junction proteins in the colorectal mucosa of miniature dachshunds (MDs) with inflammatory colorectal polyps (ICRPs). Colorectal mucosa samples were endoscopically obtained from 8 MDs with ICRPs and 8 control dogs for immunoblotting. Paraffin-embedded tissues of surgically resected inflamed lesions from another 5 MDs with ICRPs and full-thickness colorectal specimens from 5 healthy beagles were obtained for immunohistochemistry. The expression patterns of claudin-1, -2, -3, -4, -5, -7 and -8, E-cadherin and β-catenin were analyzed in the non-inflamed mucosa and inflamed mucosa of ICRPs and colorectal mucosa of control dogs by immunoblotting. The localization of these proteins in the inflamed lesions was analyzed by immunohistochemistry. The expressions of each of claudin, E-cadherin and β-catenin were not significantly different between control dogs and non-inflamed colonic mucosa from MDs with ICRPs. In contrast, only E-cadherin and β-catenin were detected in the inflamed lesions of MDs with ICRPs. By immunohistochemistry, claudin-2, -3, -4, -5 and -7, E-cadherin and β-catenin were expressed in the colorectal epithelium within the inflamed mucosa, but not in granulation tissue. Distributions of claudin-2, -3, -4, -5, and -7, E-cadherin and β-catenin in the colonic epithelium were not different between MDs with ICRPs and control dogs. These results indicated that no significant alteration was detected in several tight junction or adherence junction proteins expression in the colorectal epithelium of ICRPs.