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Cisplatin is among the most widely used anticancer drugs and known to cause a dose-limiting nephrotoxicity, which is partially dependent on the renal uptake carrier OCT2. We here report a previously unrecognized, OCT2-independent pathway of cisplatin-induced renal injury that is mediated by the organic anion transporters OAT1 and OAT3. Using transporter-deficient mouse models, we found that this mechanism regulates renal uptake of a mercapturic acid metabolite of cisplatin that acts as a precursor of a potent nephrotoxin. The function of these two transport systems can be simultaneously inhibited by the tyrosine kinase inhibitor nilotinib through noncompetitive mechanisms, without compromising the anticancer properties of cisplatin. Collectively, our findings reveal a novel pathway that explains the fundamental basis of cisplatin-induced nephrotoxicity, with potential implications for its therapeutic management.

Individuals as well as entire ecosystems are exposed to mixtures of Persistent Organic Pollutants (POPs). Previously, we showed, by a non-targeted approach, that the expression of several genes involved in carbohydrate metabolism was almost completely inhibited in the human hepatic cell line HepaRG following exposure to a mixture of the organochlorine insecticide alpha-endosulfan and 2,3,7,8 tetrachlorodibenzo-p-dioxin. In this European HEALS project, which studies the effects of the exposome on human health, we used a Physiologically Based BioKinetic model to compare the concentrations previously used in vitro with in vivo exposures for humans. We investigated the effects of these POPs on the levels of proteins, on glycogen content, glucose production and the oxidation of glucose into CO2 and correlated them to the expression of genes involved in carbohydrate metabolism as measured by RT-qPCR. Exposure to individual POPs and the mixture decreased the expression of the proteins investigated as well as glucose output (up to 82%), glucose oxidation (up to 29%) and glycogen content (up to 48%). siRNAs that specifically inhibit the expression of several xenobiotic receptors were used to assess receptor involvement in the effects of the POPs. In the HepaRG model, we demonstrate that the effects are mediated by the aryl hydrocarbon receptor and the estrogen receptor alpha, but not the pregnane X receptor or the constitutive androstane receptor. These results provide evidence that exposure to combinations of POPs, acting through different signaling pathways, may affect, more profoundly than single pollutants alone, metabolic pathways such as carbohydrate/energy metabolism and play a potential role in pollutant associated metabolic disorders.

BACKGROUND Peripheral neurotoxicity afflicts up to 90% of patients with colorectal cancer receiving oxaliplatin therapy. Oxaliplatin preferentially accumulates in and causes toxicity to peripheral sensory neurons present in the dorsal root ganglia (DRG), but mechanistic details of the transporters involved in this process remain uncertain. In the present study, we set out to unambiguously identify these transporter(s) to support the notion that oxaliplatin accumulation in DRGs is a key trigger for the development of peripheral neurotoxicity. METHODS Engineered mouse models with transporter deficiency were used to assess peripheral neurotoxicity by the Von Frey Hair test. Immunofluorescence and primary ex vivo culture of DRGs were performed to determine localization, expression, and function. Pertinent findings were validated in Sprague‐Dawley rats as a secondary model organism, while the translational feasibility of using transport inhibitors to mitigate oxaliplatin‐induced peripheral neurotoxicity was demonstrated in preclinical models of colorectal cancer. RESULTS Comparative in vitro and in vivo association studies revealed that deficiency of OCT2 confers significant protection against acute and chronic peripheral neurotoxicity, but this was not observed for the putative oxaliplatin transporters OCT3, OCTN1, OATP1B2, OATP2B1, and MATE1. Within DRGs, OCT2 was localized to satellite glial cells (SGCs), and accumulation of oxaliplatin in ex vivo cultures of SGCs was prevented by pretreatment with the OCT2 inhibitor, dasatinib. The importance of this transport system was verified in rats, where pretreatment with dasatinib in wild‐type rats recapitulated paw sensitivity phenotypes observed in OCT2‐deficient rats. Dasatinib did not influence the systemic clearance of oxaliplatin, indicating that the observed neuroprotection is directly mediated by inhibition of neuronal transport. At the applied dose and schedule that afford neuroprotection, we found that dasatinib did not negatively affect the antitumor properties of oxaliplatin against colorectal cancer cells in vitro and in vivo. CONCLUSION We identified a previously unrecognized, SGC‐specific pathway of oxaliplatin‐induced neurological injury that is mediated by the organic cationic transporter, OCT2, which can be targeted pharmacologically without compromising the anticancer properties of oxaliplatin. These findings not only shed light on the etiology of oxaliplatin‐induced neurotoxicity, but also provide a rationale for the development of targeted interventions using transporter inhibitors to mitigate a debilitating side effect associated with conventional chemotherapy.

Background: Exposure to persistent organic pollutants (POPs) has been associated with the progression of chronic liver diseases, yet the contribution of POPs to the development of fibrosis in non-alcoholic fatty liver disease (NAFLD), a condition closely linked to obesity, remains poorly documented. Objectives: We investigated the effects of subchronic exposure to low doses of the POP 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor ligand, on NAFLD progression in diet-induced obese C57BL/6J mice. Methods: Male C57BL/6J mice were fed either a 10% low-fat (LFD) or a 45% high-fat (HFD) purified diet for 14 weeks and TCDD-exposed groups were injected once a week with 5 μg/kg TCDD or the vehicle for the last 6 weeks of the diet. Results: Liver histology and triglyceride levels showed that exposure of HFD fed mice to TCDD worsened hepatic steatosis, as compared to either HFD alone or LFD plus TCDD and the mRNA levels of key genes of hepatic lipid metabolism were strongly altered in co-treated mice. Further, increased liver collagen staining and serum transaminase levels showed that TCDD induced liver fibrosis in the HFD fed mice. TCDD in LFD fed mice increased the expression of several inflammation and fibrosis marker genes with no additional effect from a HFD. Conclusions: Exposure to TCDD amplifies the impairment of liver functions observed in mice fed an enriched fat diet as compared to a low fat diet. The results provide new evidence that environmental pollutants promote the development of liver fibrosis in obesity-related NAFLD in C57BL/6J mice. Citation: Duval C, Teixeira-Clerc F, Leblanc AF, Touch S, Emond C, Guerre-Millo M, Lotersztajn S, Barouki R, Aggerbeck M, Coumoul X. 2017. Chronic exposure to low doses of dioxin promotes liver fibrosis development in the C57BL/6J diet-induced obesity mouse model. Environ Health Perspect 125:428–436; http://dx.doi.org/10.1289/EHP316

Resume La pollution chimique environnementale est suspectee de jouer un role important dans diverses pathologies. Si la relation entre certains polluants et cancers est averee, il n’en est pas de meme pour d’autres pathologies comme le diabete de type 2 ou l’obesite. Ces polluants sont des polluants organiques persistants qui sont souvent egalement des perturbateurs endocriniens. La majorite des effets s’exercent par liaison a des recepteurs, specifiques ou non des xenobiotiques, des facteurs transcriptionnels qui modifient l’expression des genes. La difficulte de l’etude de la relation entre exposition aux polluants et pathologies est due : i) a la complexite des melanges auxquels les etres vivants sont soumis de maniere chronique ; ii) a l’imperfection de modeles cellulaires ou animaux utilises pour dissequer les mecanismes moleculaires des polluants ; iii) au nombre illimite de melanges possibles. L’etude d’un petit nombre de molecules modeles dont les voies de signalisation sont connues permettra d’apprehender les interactions possibles entre les differentes classes de polluants.

LDM TEP; International audience

LDM TEP COLL; International audience; With the aim of improving the efficiency of marketed acetylcholinesterase (AChE) inhibitors in the symptomatic treatment of Alzheimer’s disease, plagued by adverse effects arising from peripheral cholinergic activation, this work reports a biological evaluation of new central AChE inhibitors based on an original “bio-oxidizable” prodrug strategy. After peripheral injection of the prodrug (1a) [IC50 > 1 mM (hAChE)] in mice, monitoring markers of central and peripheral cholinergic activation provided in vivo proof-of-concept for brain delivery of the drug (2a) [IC50 = 20 nM (hAChE)] through central redox activation of (1a). Interestingly, peripheral cholinergic activation has been shown to be limited in time, likely due to the presence of a permanent positive charge in (2a) promoting rapid elimination of the AChE inhibitor from the circulation of mice. To support these assumptions, the radiosynthesis with carbon-11 of prodrug 1a was developed for additional ex vivo studies in rats. Whole-body biodistribution of radioactivity revealed high accumulation in excretory organs along with moderate but rapid brain uptake. Radio-HPLC analyses of brain samples confirm rapid CNS penetration of [11C] (1a), while identification of [11C] (2a) and [11C] (3a) both accounts for central redox activation of (1a) and pseudoirreversible inhibition of AChE, respectively. Finally, Caco-2 permeability assays predicted metabolite (3a) as a substrate for efflux transporters (P-gp inter alia), suggesting that metabolite (3a) might possibly be actively transported out of the brain. Overall, a large body of evidence from in vivo and ex vivo studies on small animals has been collected to validate this “bio-oxidizable” prodrug approach, emerging as a very promising strategy in the rational design of selective central AChE inhibitors.

Experimental borrelia infection was induced in 62 specific--pathogen-free beagle dogs by exposure to Ixodes scapularis ticks harbouring the spirochaete Borrelia burgdorferi. Clinical signs of Lyme disease occurred in 39/62 dogs, the remaining 23 being subclinically infected. Clinical signs consisted of one to six episodes of transitory lameness with joint swelling and pain, most commonly affecting the elbow or shoulder joints. The polymerase chain reaction and culture demonstrated that the dogs remained infected for up to 581 days. At necropsy, gross findings consisted of lymphadenopathy in the area of tick attachment. Microscopical changes consisted of effusive fibrinosuppurative inflammation or nonsuppurative inflammation, or both, affecting synovial membranes, joint capsules and associated tendon sheaths. Plasma cells dominated areas of chronic inflammation, with CD3(+) T cells being present in lesser numbers. Microscopical signs of arthritis were polyarticular and more widespread than indicated by clinical signs, and most of the subclinically affected animals also had synovitis. In areas of tick attachment to the skin, hyperkeratosis and a mixture of suppurative and nonsuppurative dermatitis were encountered. Lymphadenopathy in superficial lymph nodes resulted from follicular and parafollicular hyperplasia. In 14/62 dogs, lymphoplasmacytic periarteritis and perineuritis were noted, resembling lesions found in human Lyme disease and syphilis, in which an underlying microangiopathy has been proposed.

Individuals, typically, are exposed to mixtures of environmental xenobiotics affecting multiple organs and acting through different xenosensors and pathways in species and cell-type specific manners. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and α-endosulfan are Persistent Organic Pollutants (POPs) and endocrine disruptors which act through different xenosensors and accumulate in the liver. Our objective in this HEALS study was to investigate the effects of the mixture of these POPs on gene expression in a human-derived hepatocyte cell line, HepaRG. We found that, in spite of having largely uncorrelated effects, TCDD and α-endosulfan, when mixed, alter the expression of genes. The combined effects of the mixture of the POPs significantly altered the expression of 100 genes (42 up- and 58 down-regulated) whereas the same concentration of either POP alone did not alter significantly the expression of these genes. For 32 other genes, selective inhibitory crosstalk between TCDD and α-endosulfan was observed. One of the POPs inhibited the effect, on gene expression, of the other in the mixture although, when used alone, that POP did not affect expression. The expression of another 82 genes was significantly altered (up- or down-regulated) by a single POP. The addition of the second POP either increased, in the same direction, the effect on gene expression or had no further effect. At low concentrations (0.2 nM TCDD and 1 μM α-endosulfan), the POPs still had significant effects and the levels of expression of the corresponding proteins were found to be affected for some genes. Particularly striking was the 80-90% inhibition, by the mixture, of the expression of a number of genes of several hepatic intermediary metabolic pathways (glycerolipid metabolism, FXR/RXR activation, glycolysis/gluconeogenesis, retinoid and bile acid biosynthesis), whereas each pollutant alone had only a moderate effect.

Background. Further elucidation of the consequences of Helicobacter pylori infection on gastric mucosal inflammation and gastric secretory function would be facilitated by an animal model that is susceptible to infection with H. pylori , is broadly similar in gastric physiology and pathology to people, and is amenable to repeated non-invasive evaluation. The goal of this study was to examine the interrelationship of bacterial colonization, mucosal inflammation and gastric secretory function in cats with naturally acquired H. pylori infection. Materials and Methods. Twenty clinically healthy cats with naturally acquired H. pylori infection ( cagA ‐ , picB ) and 19 Helicobacter -free cats were evaluated. Gastric colonization was determined by tissue urease activity, light microscopy, culture and PCR. The mucosal inflam matory response was evaluated by light microscopy, and by RT-PCR of the pro-inflammatory cytokines IL-1 α , IL-1 β , IL-8 and TNF- α in gastric mucosa. Gastric secretory function was assessed by measuring pentagastrin-stimulated acid secretion, fasting plasma gastrin, and antral mucosal gastrin and somatostatin immunoreactivity. Results. H. pylori colonized the pylorus, fundus and cardia in similar density. Bacteria were observed free in the lumen of gastric glands and were also tightly adherent to epithelial cells where they were associated with microvillus effacement. Mononuclear inflammation, lymphoid follicle hyperplasia, atrophy and fibrosis were observed primarily in H. pylori -infected cats, with the pylorus most severely affected. Neutrophilic and eosinophilic infiltrates, epithelial dysplasia, and upregulation of mucosal IL-1 β and IL-8 were observed solely in infected cats. Fasting plasma gastrin concen trations and pentagastrin-stimulated acid output were similar in both infected and uninfected cats. There was no relationship of bacterial colonization density or gastric inflammation to plasma gastrin concentrations or gastric acid output. Conclusions. The pattern of colonization and the mucosal inflammatory response in cats with naturally acquired H. pylori are broadly similar to those in infected people, particularly children, and non-human primates. The upregulation of IL-8 in infected cats was independent of cagA and picB . Our findings argue against a direct acid-suppressing effect of H. pylori on the gastric secretory-axis in chronically infected cats. Abbreviations: RT-PCR, reverse transcriptase poly merase chain reaction, HLO; Helicobacter-like organisms.

Introduction et but de l’etude Les populations des pays industrialises et en voie de developpement sont communement, et de plus en plus, exposees a divers polluants environnementaux. Parmi eux, les « polluants organiques persistants » (POP) sont caracterises par une longue demi-vie due a un metabolisme tres lent et a leur hydrophobicite, qui contribuent ainsi a leur stockage dans les graisses et a leur accumulation le long de la chaine alimentaire. Des etudes epidemiologiques recentes montrent que l’exposition chronique a de faibles doses de POP (en particulier les pesticides organochlores et les polychlorobiphenyles (PCBs) mais aussi les dioxines) pourrait jouer un role important, mais encore mal caracterise dans l’initiation et/ou la progression tumorale. Tres recemment, notre laboratoire a montre pour la premiere fois que la TCDD (2,3,7,8-TetraChloroDibenzo- para-Dioxine, dioxine la plus toxique) pouvait induire une fibrose hepatique chez la souris (Pierre et al, 2014), et nous cherchons a comprendre les mecanismes qui menent au developpement de cette pathologie voire a sa progression vers le cancer du foie. Materiel et methodes Le modele que nous utilisons est la lignee cellulaire HepaRG, issue d’un hepatocarcinome humain, qui presente la caracteristique de se differencier en presence de DMSO 1,5 % pendant 15 jours, en deux types cellulaires, biliaire et hepatocytaire. Il represente a l’heure actuelle, l’un des meilleurs modeles hepatocellulaires humains. Apres differenciation, les cellules sont traitees avec de la TCDD, un polluant de la famille des composes poly-aromatiques halogenes, qui utilise la voie de signalisation du AhR (recepteur aux hydrocarbures aromatiques), ainsi qu’avec d’autres ligands de ce meme recepteur (3-methylcolanthrene, PCB153). Resultats et Analyse statistique Une etude transcriptomique (puces a ADN) realisee au laboratoire sur des cellules HepaRG differenciees, a montre que la TCDD diminue de maniere drastique l’expression de certains genes du metabolisme intermediaire, et en particulier les genes codant les enzymes du metabolisme de l’alcool [diminution d’environ 80-90 % de l’expression des ARNm des CYP2E1, ADH1A-B-C (Alcool DesHydrogenase, classe I), ADH4 (classe II) et ADH6 (classe V)]. Ces enzymes sont aussi impliquees dans le metabolisme des retinoides (vitamine A), molecules qui jouent un role crucial dans le maintien d’une activite cellulaire normale. L’etude des mecanismes moleculaires de cette regulation montre qu’apres un traitement de 25nM de TCDD, le niveau d’expression des ARNm de ces enzymes diminue significativement des 8h, et apres 72h au niveau proteique. Lors d’un traitement de 24 h, cette regulation apparait neanmoins pour des concentrations de 0,1nM. La mesure de la demi-vie de l’ARNm de ces enzymes indique que leur regulation se fait au niveau transcriptionnel. Enfin, l’utilisation d’inhibiteurs pharmacologiques, de siARN et de differents ligands du AhR, montre l’implication de ce recepteur et de son partenaire nucleaire ARNT dans cette regulation. Conclusion Nos resultats suggerent que la TCDD, ainsi que d’autres POP, ligands du AhR, inhibent l’expression des enzymes du metabolisme de l’alcool via l’activation du AhR et une regulation transcriptionnelle. Nos perspectives sont 1) d’approfondir les mecanismes moleculaires de cette regulation et en particulier de savoir s’il s’agit d’une regulation directe ; 2) d’analyser les consequences de ces regulations sur le metabolisme des retinoides et le processus de cancerogenese ou de progression tumorale.

Sixteen specific-pathogen-free beagles were infected with Borrelia burgdorferi. Three groups of 4 dogs were treated with antibiotics for 30 consecutive days starting 120 days after tick exposure; 4 dogs were untreated controls. At day 420 after tick exposure and again before euthanasia, 2 dogs of each group were treated with prednisone for 14 days. All dogs contracted infection and 11 developed acute arthritis 50‐120 days after exposure. After day 120, one of 12 antibiotic-treated dogs and 2 of 4 untreated dogs became lame. Antibiotic therapy reduced the frequency of Borrelia-positivity in subsequent skin biopsy samples. After prednisone treatment, both control dogs developed severe polyarthritis. At euthanasia, single tissues of the antibiotic-treated dogs and multiple tissues of all control dogs were Borrelia-positive by polymerase chain reaction. Viable spirochetes were not recovered from antibiotic-treated dogs. Two antibiotic-treated dogs showed histologic evidence of minimal lesions, whereas all control dogs had mild polyarthritis with periarteritis. Lyme disease is caused by the tick-transmitted bacterium Borrelia burgdorferi, a spirochete that infects a wide range of mammals and birds, including humans, dogs, cats, cows, horses, and blackbirds [1‐4]. After transmission of the bacterium from the tick into the mammalian host, infection is established in the skin, and from there the spirochete disseminates through the body [5]. During the course of the infection, a variety of organs can be affected, especially the skin, large joints, the heart, and the central and peripheral nervous system. Early acute symptoms may be followed by chronic disorders [6].

The discovery of the association of Helicobacter pylori with gastritis, peptic ulcers, and gastric neoplasia has led to fundamental changes in the understanding of gastric disease in humans (5, 38, 64, 67). Investigation of the relationship of gastric disease to Helicobacter spp. in other species has resulted in the discovery of Helicobacter mustelae in ferrets with gastritis and peptic ulcers, Helicobacter acinonyx in cheetahs with severe gastritis, and Helicobacter heilmannii in pigs with gastric ulcers (11, 19, 59). Infection with Helicobacter spp. is also highly prevalent in cats, with spiral shaped bacteria 5 to 12 μm long, demonstrated in gastric biopsies from 86 to 100% of random-source cats (53, 62), 41 to 91% of clinically healthy pet cats (26, 30, 49, 73), 93 to 100% of laboratory cats (9, 54, 70), and 57 to 76% of cats with recurrent vomiting (26, 33, 73). H. pylori has been observed in a group of laboratory cats, but not pet cats, and is associated with gastritis in cats (22, 28). Excluding cats with H. pylori infection, the gastric Helicobacter-like organisms (HLOs) in cats are morphologically indistinguishable by light microscopy, but have been classified into several Helicobacter spp. on the basis of cultural characteristics, 16S rRNA sequencing, DNA hybridization, PCR with species-specific primers, electron microscopic appearance, and protein profiling (9, 15, 34, 36, 49, 51). To date, Helicobacter felis, H. heilmannii, Helicobacter pametensis, and H. felis- and H. heilmannii-like organisms have been identified (9, 15, 34, 36, 49, 51). Despite their prevalence, the relationship of Helicobacter spp. to disease in cats is unresolved. Gastritis and glandular degeneration accompany infection in some, but not all, infected cats, and many are asymptomatic despite infection (30, 33, 53, 62, 73). Investigations of the pathogenicity of large gastric HLOs in cats have focused on describing the infecting bacteria and histopathology in cats with naturally acquired infections, and only a few studies have included Helicobacter-free cats (26, 30, 73). The host immune response to infection and gastric secretory function have not been examined. Consideration of those factors is important, because H. pylori infection in people is associated with gastritis, the induction of proinflammatory cytokines, seroconversion, and changes in gastric function. Increased acid secretion is associated with antral gastritis and duodenal ulceration (12, 13, 47), whereas achlorhydria is observed shortly after infection with H. pylori and when the gastric fundus and body is inflamed or atrophied (14, 44, 46, 65). Hypergastrinemia is a consistent finding in H. pylori-infected people and is present in asymptomatic individuals, those with achlorhydria, and those with duodenal ulcers (13, 27). Eradication of H. pylori has been associated with amelioration of gastritis and hypergastrinemia, decreased acid secretion in people with acid hypersecretion, and increased acid secretion in achlorhydric patients (13, 14, 47). It is presently unclear if Helicobacter spp. other than H. pylori can induce such changes and whether the alterations in gastric function which accompany infection with H. pylori are a consequence of bacterial products, such as urease, ammonia, or acid inhibitory factors, or the inflammatory response evoked by the bacterium. There is a clear need to determine if H. felis is a gastric pathogen in cats and for animal models that will enable evaluation of the consequences of Helicobacter colonization for somatostatin and gastrin physiology, acid secretion, and mucosal inflammation. We report here the evaluation of gastric histopathology, antral interleukin 1α (IL-1α), IL-1β, and tumor necrosis factor alpha (TNF-α) mRNA expression, acid secretion, plasma gastrin, antral somatostatin and gastrin immunoreactivity, and circulating anti-H. felis immunoglobulin G (IgG) after experimental infection of cats with H. felis.

Twenty 6-week-old specific-pathogen-free beagles were infected with Borrelia burgdorferi by tick challenge, and five uninfected dogs served as controls. During the study, all dogs were monitored for infection, clinical signs, and antibody response against B. burgdorferi. During episodes of lameness or postmortem, synovial fluids from each dog were examined for volume, cell number, polymorphonuclear leukocyte (PMN) content, cell viability, and chemotactic activity. Twenty-five tissues collected postmortem from each dog were tested for interleukin-8 (IL-8) mRNA, tumor necrosis factor alpha (TNF-alpha) mRNA, presence of live spirochetes, and histopathological changes. Thirteen infected dogs (group A), which seroconverted rapidly (maximum titers within 50 to 90 days), developed acute and severe mono- or oligoarthritis almost exclusively in the limb closest to the tick bite (median incubation period, 66 days). Synovial fluids of the arthritic joints collected during episodes of lameness had significantly elevated volume, cell count, PMN proportion, cell viability, and chemotactic activity for PMNs. The remaining joints of the same animals contained synovial fluids with elevated chemotactic activity and cell viability. Twelve dogs tested positive for IL-8 mRNA in multiple tissues (synovia, pericardium, and peritoneum), and 10 dogs expressed TNF-alpha mRNA, but only in the tributary lymph nodes of the inflamed joints. Histological examinations revealed severe poly- or oligoarthritis and moderate to severe cortical hyperplasia in draining lymph nodes of the inflamed joints in all 13 dogs. Seven infected dogs with mild or no clinical signs (group B) seroconverted slowly (peak titers after 90 days), and only some joint fluids showed chemotactic activity, which on average was lower than that in inflamed and noninflamed joints from dogs in group A. Four dogs expressed IL-8 mRNA (in the synovia and pericardium), and three dogs had TNF-alpha mRNA in tributary lymph nodes. Histologically, nonsuppurative arthritis was found in multiple joints, and mild to moderate cortical hyperplasia was found in draining lymph nodes. Five uninfected dogs without lameness (group C) had normal synovial fluids and tissues. In all infected dogs, live spirochetes were demonstrated more frequently in tissues of the somatic quadrant closest to the tick bite than in tissues further from the site of infection, suggesting that dissemination of B. burgdorferi occurs more by migration than by blood-borne spread. From these studies employing a canine model of B. burgdorferi infection, we conclude that IL-8 is involved in the pathogenesis of acute Lyme arthritis.