Presence of alternative lengthening of telomeres mechanism in patients with glioblastoma identifies a less aggressive tumor type with longer survival.

Patients with glioblastoma (GBM) have variable clinical courses, but the factors that underlie this heterogeneity are not understood. To determine whether the presence of the telomerase-independent alternative lengthening of telomeres (ALTs) mechanism is a significant prognostic factor for survival, we performed a retrospective analysis of 573 GBM patients. The presence of ALT was identified in paraffin sections using a combination of immunofluorescence for promyelocytic leukemia body and telomere fluorescence in situ hybridization. Alternative lengthening of telomere was present in 15% of the GBM patients. Patients with ALT had longer survival that was independent of age, surgery, and other treatments. Mutations in isocitrate dehydrogenase (IDH1mut) 1 frequently accompanied ALT, and in the presence of both molecular events, there was significantly longer overall survival. These data suggest that most ALT+ tumors may be less aggressive proneural GBMs, and the better prognosis may relate to the set of genetic changes associated with this tumor subtype. Despite improved overall survival of patients treated with the addition of chemotherapy to radiotherapy and surgery, ALT and chemotherapy independently provided a survival advantage, but these factors were not found to be additive. These results suggest a critical need for developing new therapies to target these specific GBM subtypes.

Inhibition of mouse mammary tumor virus-induced T cell responses in vivo by antibodies to an open reading frame protein.

Minor lymphocyte stimulating (Mls) antigens specifically stimulate T cell responses that are restricted to particular T cell receptor (TCR) beta chain variable domains. The Mls phenotype is genetically controlled by an open reading frame (orf) located in the 3' long terminal repeat of mouse mammary tumor virus (MMTV); however, the mechanism of action of the orf gene product is unknown. Whereas predicted orf amino acid sequences show strong overall homology, the 20-30 COOH-terminal residues are strikingly polymorphic. This polymorphic region correlates with TCR V beta specificity. We have generated monoclonal antibodies to a synthetic peptide encompassing the 19 COOH-terminal amino acid residues of Mtv-7 orf, which encodes the Mls-1a determinant. We show here that these antibodies block Mls responses in vitro and can interfere specifically with thymic clonal deletion of Mls-1a reactive V beta 6+ T cells in neonatal mice. Furthermore, the antibodies can inhibit V beta 6+ T cell responses in vivo to an infectious MMTV that shares orf sequence homology and TCR specificity with Mtv-7. These results confirm the predicted extracellular localization of the orf COOH terminus and imply that the orf proteins of both endogenous and exogenous MMTV interact directly with TCR V beta.

Analysis of hepatitis C virus resistance to silibinin in vitro and in vivo points to a novel mechanism involving nonstructural protein 4B.

Intravenous silibinin (SIL) is an approved therapeutic that has recently been applied to patients with chronic hepatitis C, successfully clearing hepatitis C virus (HCV) infection in some patients even in monotherapy. Previous studies suggested multiple antiviral mechanisms of SIL; however, the dominant mode of action has not been determined. We first analyzed the impact of SIL on replication of subgenomic replicons from different HCV genotypes in vitro and found a strong inhibition of RNA replication for genotype 1a and genotype 1b. In contrast, RNA replication and infection of genotype 2a were minimally affected by SIL. To identify the viral target of SIL we analyzed resistance to SIL in vitro and in vivo. Selection for drug resistance in cell culture identified a mutation in HCV nonstructural protein (NS) 4B conferring partial resistance to SIL. This was corroborated by sequence analyses of HCV from a liver transplant recipient experiencing viral breakthrough under SIL monotherapy. Again, we identified distinct mutations affecting highly conserved amino acid residues within NS4B, which mediated phenotypic SIL resistance also in vitro. Analyses of chimeric viral genomes suggest that SIL might target an interaction between NS4B and NS3/4A. Ultrastructural studies revealed changes in the morphology of viral membrane alterations upon SIL treatment of a susceptible genotype 1b isolate, but not of a resistant NS4B mutant or genotype 2a, indicating that SIL might interfere with the formation of HCV replication sites. CONCLUSION: Mutations conferring partial resistance to SIL treatment in vivo and in cell culture argue for a mechanism involving NS4B. This novel mode of action renders SIL an attractive candidate for combination therapies with other directly acting antiviral drugs, particularly in difficult-to-treat patient cohorts.

Characterization of tumor reactive CD8 T cells induced by peptide vaccination in melanoma patients

ABSTRACT¦Naturally acquired tumor-specific T-cells can be detected in most advanced cancer patients.¦Yet, they often fail to control or eliminate the disease, in contrast to many virus-specific CD8¦T lymphocytes. Therapeutic vaccines aim at inducing and boosting specific T-cells mediated¦immunity to reduce tumor burden. The properties of CD8 T-cells required for protection from¦infectious disease and cancer are only partially characterized.¦The objectives of this study were to assess effector functions, stage of differentiation and¦clonotype selection of tumor-reactive T lymphocytes following peptide vaccination in¦melanoma patients over time. Results were compared to protective viral-specific T-cell¦responses found in healthy individuals. We also characterized dominant versus low/non¦dominant T-cell clonotypes with the aim to further understand the in vivo function of each set¦of frequency-based specific T-cells.¦Here we developed and applied a novel approach for molecular and functional analysis of¦single T lymphocytes ex vivo. T-cell receptor (TCR) clonotype mapping revealed rapid¦selection and expansion of co-dominant T-cell clonotypes, which made up the majority of the¦highly differentiated "effector" T-cells, but only 25% of the less differentiated "effectormemory"¦cells, mostly composed of non-dominant clonotypes. Moreover, we show that¦advanced effector cell differentiation was indeed clonotype-dependent. Surprisingly, however,¦the acquisition of effector functions (cytokine production, killing) was clonotype-independent.¦Vaccination of melanoma patients with native peptide induced competent effector function in¦both dominant and non-dominant clonotypes, suggesting that most if not all clonotypes¦participating in a T-cell response have the potential to develop equal functional competence.¦In contrast, many T-cells remained poorly functional after vaccination with analog peptide,¦despite similar clonotype-dependent differentiation. Our findings show that the type of¦peptide vaccine has a critical influence on the selection and functional activation of the¦clonotypic T-cell repertoire. They also show that systematic assessment of individual T-cells¦identifies the cellular basis of immune responses, contributing to the rational development of¦vaccines.

Protective role of amantadine in mitochondrial dysfunction and oxidative stress mediated by hepatitis C virus protein expression.

Amantadine is an antiviral and antiparkinsonian drug that has been evaluated in combination therapies against hepatitis C virus (HCV) infection. Controversial results have been reported concerning its efficacy, and its mechanism of action remains unclear. Data obtained in vitro suggested a role of amantadine in inhibiting HCV p7-mediated cation conductance. In keeping with the fact that mitochondria are responsible to ionic fluxes and that HCV infection impairs mitochondrial function, we investigated a potential role of amantadine in modulating mitochondrial function. Using a well-characterized inducible cell line expressing the full-length HCV polyprotein, we found that amantadine not only prevented but also rescued HCV protein-mediated mitochondrial dysfunction. Specifically, amantadine corrected (i) overload of mitochondrial Ca(2+); (ii) inhibition of respiratory chain activity and oxidative phosphorylation; (iii) reduction of membrane potential; and (iv) overproduction of reactive oxygen species. The effects of amantadine were observed within 15 min following drug administration and confirmed in Huh-7.5 cells transfected with an infectious HCV genome. These effects were also observed in cells expressing subgenomic HCV constructs, indicating that they are not mediated or only in part mediated by p7. Single organelle analyzes carried out on isolated mouse liver mitochondria demonstrated that amantadine induces hyperpolarization of the membrane potential. Moreover, amantadine treatment increased the calcium threshold required to trigger mitochondrial permeability transition opening. In conclusion, these results support a role of amantadine in preserving cellular bioenergetics and redox homeostasis in HCV-infected cells and unveil an effect of the drug which might be exploited for a broader therapeutic utilization.

Adiponectin and C-reactive protein are positively associated with microalbuminuria in an adult Caucasian population

Objective: Microalbuminuria (MAU) is a marker of early kidney injury and cardiovascular risk. We assessed the association of MAU with plasma adiponectin, leptin and hsCRP, as inflammatory markers, accounting for hypertension, diabetes and obesity. Design and methods: Population based, cross-sectional study in Caucasian subjects aged 35 to 75 years in Lausanne, Switzerland. MAU, measured on spot morning urine, was used either as a continuous (MAU) or dichotomized variable (MA defined as MAU >2.5 and >3.5 mg/mmol creatinine in men and women, respectively). Results: The 2955 women (age 53.3 ± 10.7, mean ± SD years) had mean body mass index (BMI) 24.9 ± 4.5 kg/m. The 2479 men (age 53.1 ± 10.8 years) had mean BMI 27.0 ± 3.9 kg/m². Median hsCRP was 1.3 and 1.3 mg/L, median adiponectin 6.2 and 10.6 mg/mL in men and women, respectively. MA prevalence was 4.9% in women and 9.8% in men. In multivariate regression analysis adjusting for potential confounders (age, sex, hypertension, diabetes, eGFR, BMI, percent fat mass, insulin and smoking), log-transformed MAU was positively associated with hsCRP (P <0.001) and adiponectin (P = 0.002), but not with leptin. The association of adiponectin with MAU was stronger in subjects with low hsCRP, and vice versa (P interaction <0.001). Conclusion: Adiponectin and hsCRP are significant positive determinants of MAU, independently of diabetes, hypertension and fat mass. A negative interaction between hsCRP and adiponectin was found for their effect on MAU. Whether hyperadiponectinemia represents an adequate protective response to vascular stress or has negative causal impact on the development of MAU should be assessed in further studies.

Reactive rise in blood pressure upon cuff inflation : cuff inflation at the arm causes a greater rise in pressure than at the wrist in hypertensive patients

Résumé en français: Il est admis que l'inflation d'une manchette à pression au niveau du bras engendre une augmentation réactionnelle de la tension artérielle qui peut être le résultat d'une gêne lors de l'inflation et peut diminuer la précision de la mesure. Dans cette étude, nous comparons séquentiellement l'augmentation de la tension artérielle lorsque la manchette à pression est positionnée au niveau du bras et au niveau du poignet. Nous avons étudié un collectif de 34 participants normotendus et 34 patients hypertendus. Chacun d'eux était équipé de deux manchettes à pression, l'une au niveau du bras et l'autre au niveau du poignet. Nous avons randomisé l'ordre d'inflation des manchettes ainsi que la pression d'inflation maximale (180mmHg versus 240mmHg). Trois mesures étaient effectuées pour chaque pression d'inflation maximale, ceci au bras comme poignet, et leur séquence était également randomisée. En parallèle, un enregistrement continu de la tension artérielle avait lieu au niveau du majeur de la main opposée à l'aide d'un photoplethysmographe. Cette valeur était considérée comme la valeur de tension artérielle au repos. Pour les participants normotendus, aucune différence statistiquement significative n'a pu être mise en évidence en lien avec la position de la manchette à pression, ceci indépendamment de la pression d'inflation maximale. Variation de la pression systolique à 180 mmHg: 4.3+/-3.0 mmHg au bras et 3.7+/-2.9 mmHg au poignet (p=ns), à 240 mmHg: 5.5+/-3.9 au bras et 4.2+/-2.7 mmHg au poignet (p=0.052). En revanche, concernant les patients hypertendus, une augmentation significative de la tension artérielle a été mise en évidence entre le bras et le poignet. Ceci pour les valeurs de tension artérielle systolique et diastolique et quelle que soit la pression d'inflation maximale utilisée. Augmentation de la pression artérielle systolique 6.513.5 mmHg au bras et 3.812.1mmHg au poignet pour une pression d'inflation maximale de 180 mmHg (p<0.01) et respectivement 6.413.5 mmHg et 4.713.0 mmHg pour 240 mmHg (p=0.01). L'augmentation des valeurs de tension artérielle était indépendante de la valeur tensionnelle de base. Ces résultats montrent que les patients hypertendus réagissent significativement moins à l'inflation d'une manchette ä pression lorsque celle-ci est positionnée au niveau du poignet par rapport au bras, ceci indépendamment des valeurs de tension artérielle de base des patients. Nous pouvons donc suggérer que l'inflation d'une manchette à pression cause moins de désagrément lorsqu'elle est placée au niveau du poignet, notamment chez les patients hypertendus et qu'elle peut être une alternative à la mesure standard au niveau du bras.

Bacterial-induced protection against allergic inflammation through a multicomponent immunoregulatory mechanism.

Background Airborne microbial products have been reported to promote immune responses that suppress asthma, yet how these beneficial effects take place remains controversial and poorly understood. Methods We exposed mice to the bacterium Escherichia coli and subsequently induced allergic airway inflammation through sensitization and intranasal challenge with ovalbumin. Results Pulmonary exposure to the bacterium Escherichia coli leads to a suppression of allergic airway inflammation. This immune modulation was neither mediated by the induction of a T helper 1 (Th1) response nor regulatory T cells; however, it was dependent on Toll-like receptor 4 (TLR4) but did not involve TLR desensitisation. Dendritic cell migration to the draining lymph nodes and activation of T cells was unaffected by prior exposure to E.coli, while dendritic cells in the lung displayed a less activated phenotype and had impaired antigen presentation capacity. Consequently, in situ Th2 cytokine production was abrogated. The suppression of airway hyper-responsiveness was mediated through the recruitment of gd T cells; however, the suppression of dendritic cells and T cells was mediated through a distinct mechanism that could not be overcome by the local administration of activated dendritic cells, or by the in vivo administration of tumour necrosis factor a. Conclusion Our data reveal a localized immunoregulatory pathway that acts to protect the airways from allergic inflammation.

NO rebinding to myoglobin: a reactive molecular dynamics study.

The rebinding of NO to myoglobin after photolysis is studied using the 'reactive molecular dynamics' method. In this approach the energy of the system is evaluated on two potential energy surfaces that include the heme-ligand interactions which change between liganded and unliganded myoglobin. This makes it possible to take into account in a simple way, the high dimensionality of the transition seam connecting the reactant and product states. The dynamics of the dissociated NO molecules are examined, and the geometrical and energetic properties of the transition seam are studied. Analysis of the frequency of recrossing shows that the height of the effective rebinding barrier is dependent on the time after photodissociation. This effect is due mainly to protein relaxation and may contribute to the experimentally observed non-exponential rebinding rate of NO, as has been suggested previously.

Methicillin-resistant Staphylococcus aureus resensitization by protein synthesis inhibitors : proposal for a mechanism

RESUME Staphylococcus aureus est un important pathogène à gram-positif, à la fois responsable d'infections nosocomiales et communautaires. Le S. aureus résistant à la méthicilline est intrinsèquement résistant aux bêta-lactamines, inhibiteurs de la synthèse de la paroi bactérienne, grâce à une enzyme nouvellement acquise, la protéine liant la pénicilline 2A, caractérisée par une faible affinité pour ces agents et pouvant poursuivre la synthèse de la paroi, alors que les autres enzymes sont bloquées. Ce micro-organisme a également développé des résistances contre quasiment tous les antibiotiques couramment utilisés en clinique. Parallèlement au développement de molécules entièrement nouvelles, il peut être utile d'explorer d'éventuelles caractéristiques inattendues de médicaments déjà existants, par exemple en les combinant, dans l'espoir d'un potentiel effet synergique. Comprendre les mécanismes de tels effets synergiques pourrait contribuer à la justification de leur utilisation clinique potentielle. Récemment, un effet synergique contre le S. aureus résistant à la méthicilline a été décrit entre la streptogramine quinupristine-datfopristine et les bêta-lactamines, aussi bien in vitro qu'in vivo. Le présent travail a pour but de proposer un modèle pour le mécanisme de cette interaction positive et de l'étendre à d'autres classes d'antibiotiques. Premièrement, un certain nombre de méthodes microbiologiques ont permis de mieux cerner la nature de cette interaction, en montrant qu'elle agissait spécifiquement sur le S. aureus résistant à la méthicilline et qu'elle était restreinte à l'association entre inhibiteurs de la synthèse des protéines et bêta-lactamines. Deuxièmement, L'observation de l'influence des inhibiteurs de la synthèse des protéines sur la machinerie de la paroi bactérienne, c'est-à-dire sur l'expression des protéines liant la pénicilline, responsables de la synthèse du peptidoglycan, a montré une diminution de la quantité de ta protéine liant la pénicilline 2, connue pour posséder une activité de transglycosylation, indispensable au bon fonctionnement de la protéine liant la pénicilline 2A, responsable de la résistance à la méthicilline. Troisièmement, l'analyse fine de la composition du peptidoglycan extrait de bactéries, avant ou après traitement par des inhibiteurs de la synthèse des protéines, a montré des altérations corrélant avec leur capacité à agir en synergie avec les bêta-lactamines contre S. aureus résistant à ta méthicilline. Ces altérations dans les muropeptides pourraient représenter une signature de la diminution de la quantité de la protéine liant la pénicilline 2. Le modèle mécanistique retenu considère que les inhibiteurs de la synthèse des protéines pourraient diminuer l'expression de la protéine Liant la pénicilline 2, indispensable à la résistance à la méthiciltine, et que ce déséquilibre dans les enzymes synthétisant la paroi bactérienne pourrait générer une signature dans les muropeptides. SUMMARY Staphylococcus aureus is a major gram-positive pathogen causing both hospital-acquired and community-acquired infections. Methicillin- resistant Staphylococcus aureus is intrinsically resistant to the cell wall inhibitors beta-lactams by virtue of a newly acquired cell-wall-building enzyme, tow-affinity penicillin-binding protein 2A, which can build the wall when other penicillin-binding proteins are blocked. Moreover, the microorganism has developed resistance to virtually all non-experimental antibiotics. In addition of producing entirely new molecules, it is useful to explore unexpected features of existing drugs, for example by using them in combination, expecting drug synergisms. Understanding the mechanisms of such synergisms would help justify their putative clinical utilization. Recently, a synergism between the streptogramin quinupristin-dalfopristin and beta-lactams was reported against methicillin-resistant S. aureus, both in vitro and in vivo. The present work intends to propose a model for the mechanism of this positive interaction and to extend it to other drug classes. First, microbiological experimentation helped better defining the nature of this interaction, restricting it to methicillin-resistant S. aureus, and to the association of protein synthesis inhibitors with beta-lactams. Second, the observation of inhibitors of protein synthesis influence on the cell-wall-building machinery, i.e. on the expression of penicillin-binding proteins responsible for peptidoglycan synthesis, showed a decrease in the amount of penicillin-binding protein 2, known to provide a transglycosylase activity for glycan chain elongation, indispensable for the functionality of the low-affinity penicillin-binding protein 2A responsible for methicillin resistance. Third, the fine analysis of the peptidoglycan composition purified from bacteria before or after treatment with inhibitors of protein synthesis showed alterations that correlated with their ability to synergize with beta-lactams against methicillin-resistant S. aureus. These muropeptide alterations could be the signature of decrease in the amount of penicillin-binding protein 2. The retained mechanistic model is that inhibitors of protein synthesis could decrease the expression of penicillin-binding protein 2, wich is indispensable for methicillin-resistance, and that this imbalance in cell-wall-building enzymes could generate a muropeptide signature.

Positional scanning-synthetic peptide library-based analysis of self- and pathogen-derived peptide cross-reactivity with tumor-reactive Melan-A-specific CTL.

Synthetic combinatorial peptide libraries in positional scanning format (PS-SCL) have recently emerged as a useful tool for the analysis of T cell recognition. This includes identification of potentially cross-reactive sequences of self or pathogen origin that could be relevant for the understanding of TCR repertoire selection and maintenance, as well as of the cross-reactive potential of Ag-specific immune responses. In this study, we have analyzed the recognition of sequences retrieved by using a biometric analysis of the data generated by screening a PS-SCL with a tumor-reactive CTL clone specific for an immunodominant peptide from the melanocyte differentiation and tumor-associated Ag Melan-A. We found that 39% of the retrieved peptides were recognized by the CTL clone used for PS-SCL screening. The proportion of peptides recognized was higher among those with both high predicted affinity for the HLA-A2 molecule and high predicted stimulatory score. Interestingly, up to 94% of the retrieved peptides were cross-recognized by other Melan-A-specific CTL. Cross-recognition was at least partially focused, as some peptides were cross-recognized by the majority of CTL. Importantly, stimulation of PBMC from melanoma patients with the most frequently recognized peptides elicited the expansion of heterogeneous CD8(+) T cell populations, one fraction of which cross-recognized Melan-A. Together, these results underline the high predictive value of PS-SCL for the identification of sequences cross-recognized by Ag-specific T cells.

Insulin-like growth factor-I and C-reactive protein during pregnancy and maternal risk of non-epithelial ovarian cancer: a nested case-control study.

BACKGROUND: Insulin-like growth factor-I (IGF-I) and C-reactive protein (CRP) may be positively associated with the risk of epithelial ovarian cancer (EOC) but no previous studies have investigated their associations with non-epithelial ovarian cancers (NEOC). METHODS: A case-control study was nested within the Finnish Maternity Cohort. Case subjects were 58 women diagnosed with sex cord-stromal tumors (SCST) and 30 with germ cell tumors (GCT) after recruitment. Control subjects (144 for SCST and 74 for GCT) were matched for age, parity, and date of blood donation of the index case. RESULTS: Doubling of IGF-I concentration was not related to maternal risk of either SCST (OR 0.97, 95% CI 0.58-1.62) or GCT (OR 1.13, 95% CI 0.51-2.51). Similarly, doubling of CRP concentrations was not related to maternal risk of either SCST (OR 1.10, 95% CI 0.85-1.43) or GCT (OR 0.93, 95% CI 0.68-1.28). CONCLUSIONS: Pre-diagnostic IGF-I and CRP concentrations during the first trimester of pregnancy were not associated with increased risk of NEOC in the mother. Risk factors for NEOC may differ from those of EOC.

No implication of thromboxane prostanoid receptors in reactive hyperemia of skin and skeletal muscle in human forearm.

There is evidence that reactive hyperemia (ie, the transient increase of blood flow above resting level after a short period of ischemia) could be negatively modulated by vasoconstrictor prostanoids. The present study tested whether pharmacological blockade of the thromboxane prostanoid receptors with the specific antagonist S18886 (terutroban) would amplify reactive hyperemia in human skin and skeletal muscle. Twenty healthy young male volunteers were enrolled in a randomized, blinded, crossover trial of oral S18886 30 mg/d for 5 days versus placebo. Reactive hyperemia was evaluated in forearm skin and skeletal muscle, after occlusion of the brachial artery with a pneumatic cuff inflated at suprasystolic pressure. Blood flow was measured with laser Doppler imaging (skin) and strain gauge venous occlusion plethysmography (muscle). On the first and last day of each treatment period, recordings of reactive hyperemia were obtained immediately before and 2 hours after drug intake. Whether in forearm muscle or skin, S18886 had no discernible effect on peak postocclusion blood flow, nor on the global hyperemic response as quantified by the area under curve. These results do not support that thromboxane prostanoid receptor activation could exert a moderating influence on reactive hyperemia in human skin and skeletal muscle, at least in young subjects.

An autoregulatory loop controlling CYP1A1 gene expression: role of H(2)O(2) and NFI.

Cytochrome P450 1A1 (CYP1A1), like many monooxygenases, can produce reactive oxygen species during its catalytic cycle. Apart from the well-characterized xenobiotic-elicited induction, the regulatory mechanisms involved in the control of the steady-state activity of CYP1A1 have not been elucidated. We show here that reactive oxygen species generated from the activity of CYP1A1 limit the levels of induced CYP1A1 mRNAs. The mechanism involves the repression of the CYP1A1 gene promoter activity in a negative-feedback autoregulatory loop. Indeed, increasing the CYP1A1 activity by transfecting CYP1A1 expression vectors into hepatoma cells elicited an oxidative stress and led to the repression of a reporter gene driven by the CYP1A1 gene promoter. This negative autoregulation is abolished by ellipticine (an inhibitor of CYP1A1) and by catalase (which catalyzes H(2)O(2) catabolism), thus implying that H(2)O(2) is an intermediate. Down-regulation is also abolished by the mutation of the proximal nuclear factor I (NFI) site in the promoter. The transactivating domain of NFI/CTF was found to act in synergy with the arylhydrocarbon receptor pathway during the induction of CYP1A1 by 2,3,7,8-tetrachloro-p-dibenzodioxin. Using an NFI/CTF-Gal4 fusion, we show that NFI/CTF transactivating function is decreased by a high activity of CYP1A1. This regulation is also abolished by catalase or ellipticine. Consistently, the transactivating function of NFI/CTF is repressed in cells treated with H(2)O(2), a novel finding indicating that the transactivating domain of a transcription factor can be targeted by oxidative stress. In conclusion, an autoregulatory loop leads to the fine tuning of the CYP1A1 gene expression through the down-regulation of NFI activity by CYP1A1-based H(2)O(2) production. This mechanism allows a limitation of the potentially toxic CYP1A1 activity within the cell.