Presence of immunoglobulin E-expressing antibody-secreting cells in the dermis close to bullous pemphigoid lesions

Antibody-secreting cells (ASCs) produce immunoglobulin (Ig) G and IgE autoantibodies in secondary lymphoid organs. Evidence also suggests their existence in the skin in various chronic inflammatory conditions, and in association with CXCL12 and CXCL13, they regulate the recruitment/survival of ASCs and germinal center formation to generate ASCs, respectively. However, the presence of IgG and IgE in bullous pemphigoid (BP) lesions needs to be addressed. Here, we aimed to analyse BP skin for the presence of IgG and IgE and the factors contributing to their generation, recruitment, and persistence. Skin samples from 30 patients with BP were stained to identify ASCs and the immunoglobulin type they expressed. The presence of tertiary lymphoid organ (TLO) elements, which generate ASCs in non-lymphoid tissues, and the chemokines CXCL12 and CXCL13, which regulate the migration/persistence of ASCs in lymphoid tissues and formation of TLOs, respectively, were evaluated in BP skin. BP skin harboured ASCs expressing the two types of antibodies IgG and IgE. ASCs were found in high-grade cellular aggregates containing TLO elements: T cells, B cells, CXCL12+ cells, CXCL13+ cells and high endothelial venules. IgG+ ASCs were detected among these aggregates, whereas IgE+ ASCs were dispersed throughout the dermis. CXCL12+ fibroblast-like cells were located close to ASCs. The inflammatory microenvironment of BP lesions may contribute to the antibody load characteristic of the skin of patients with BP by providing a site for the presence of ASCs. CXCL13 and CXCL12 expression may contribute to the generation and recruitment/survival of ASCs, respectively.

THBS1-producing tumor-infiltrating monocyte-like cells contribute to immunosuppression and metastasis in colorectal cancer

Mesenchymal activation, characterized by dense stromal infiltration of immune and mesenchymal cells, fuels the aggressiveness of colorectal cancers (CRC), driving progression and metastasis. Targetable molecules in the tumor microenvironment (TME) need to be identified to improve the outcome in CRC patients with this aggressive phenotype. This study reports a positive link between high thrombospondin-1 (THBS1) expression and mesenchymal characteristics, immunosuppression, and unfavorable CRC prognosis. Bone marrow-derived monocyte-like cells recruited by CXCL12 are the primary source of THBS1, which contributes to the development of metastasis by inducing cytotoxic T-cell exhaustion and impairing vascularization. Furthermore, in orthotopically generated CRC models in male mice, THBS1 loss in the TME renders tumors partially sensitive to immune checkpoint inhibitors and anti-cancer drugs. Our study establishes THBS1 as a potential biomarker for identifying mesenchymal CRC and as a critical suppressor of antitumor immunity that contributes to the progression of this malignancy with a poor prognosis.

Exploring the role of Janus kinase (JAK) in atopic dermatitis: a review of molecular mechanisms and therapeutic strategies

Recent studies have demonstrated that Janus kinase (JAK) plays a crucial role in signal transduction by directly affecting various cytokine receptors involved in inflammatory diseases such as atopic dermatitis (AD). Large-scale clinical trials on AD utilizing JAK inhibitors and biologic reagents, such as dupilumab, which targets the IL-4Rα receptor subunit of the Th2 cytokines IL-4 and IL-13, have yielded highly favorable results in comparison to traditional therapies. This indicates that therapeutic strategies based on molecular biology are efficacious in clinical settings. However, in September 2021, the U.S. Food and Drug Administration (FDA) indicated that tofacitinib, a JAK inhibitor, may carry various risks, including severe heart disease. Similar concerns have been raised for other JAK inhibitors, and further safety evaluations are underway. Thus, human biology involving JAKs appeared more complicated than we expected. In this article, we provide an overview of the molecular mechanisms of AD and examine the molecular targeting drugs for AD from the perspective of JAK-related biology.

Interleukin-13 inhibition by tralokinumab reduces inducible T-cell costimulator-positive innate lymphoid cells in skin lesions of atopic dermatitis

Despite the low frequency of skin ILCs and the limited number of samples analyzed in this study, our data indicate that ICOS+ ILCs express IL-13Rα1 and that the density of ICOS+ ILCs decreased four weeks after initiation of treatment with tralokinumab.

Summary of the current status of clinically diagnosed cases of Schnitzler syndrome in Japan

BACKGROUND

Schnitzler syndrome is a rare disorder with chronic urticaria, and there is no report summarizing the current status in Japan.

METHODS

A nationwide survey of major dermatology departments in Japan was conducted in 2019. We further performed a systematic search of PubMed and Ichushi-Web, using the keywords "Schnitzler syndrome" and "Japan" then contacted the corresponding authors or physicians for further information.

RESULTS

Excluding duplicates, a total of 36 clinically diagnosed cases were identified from 1994 through the spring of 2022, with a male to female ratio of 1:1. The median age of onset was 56.5 years. It took 3.3 years from the first symptom, mostly urticaria, to reach the final diagnosis. The current status of 30 cases was ascertained; two patients developed B-cell lymphoma. SchS treatment was generally effective with high doses of corticosteroids, but symptoms sometimes recurred after tapering. Colchicine was administered in 17 cases and was effective in 8, but showed no effect in the others. Tocilizumab, used in six cases, improved laboratory abnormalities and symptoms, but lost its efficacy after several years. Rituximab, used in five cases, was effective in reducing serum IgM levels or lymphoma mass, but not in inflammatory symptoms. Four cases were treated with IL-1 targeting therapy, either anakinra or canakinumab, and achieved complete remission, except one case with diffuse large B-cell lymphoma.

CONCLUSIONS

Since Schnitzler syndrome is a rare disease, the continuous collection and long-term follow-up of clinical information is essential for its appropriate treatment and further understanding of its pathophysiology.

Waves of layered immunity over innate lymphoid cells

Innate lymphoid cells (ILCs) harbor tissue-resident properties in border zones, such as the mucosal membranes and the skin. ILCs exert a wide range of biological functions, including inflammatory response, maintenance of tissue homeostasis, and metabolism. Since its discovery, tremendous effort has been made to clarify the nature of ILCs, and scientific progress revealed that progenitor cells of ILC can produce ILC subsets that are functionally reminiscent of T-cell subsets such as Th1, Th2, and Th17. Thus, now it comes to the notion that ILC progenitors are considered an innate version of naïve T cells. Another important discovery was that ILC progenitors in the different tissues undergo different modes of differentiation pathways. Furthermore, during the embryonic phase, progenitor cells in different developmental chronologies give rise to the unique spectra of immune cells and cause a wave to replenish the immune cells in tissues. This observation leads to the concept of layered immunity, which explains the ontology of some cell populations, such as B-1a cells, γδ T cells, and tissue-resident macrophages. Thus, recent reports in ILC biology posed a possibility that the concept of layered immunity might disentangle the complexity of ILC heterogeneity. In this review, we compare ILC ontogeny in the bone marrow with those of embryonic tissues, such as the fetal liver and embryonic thymus, to disentangle ILC heterogeneity in light of layered immunity.

CCL2‒CCR2 Signaling in the Skin Drives Surfactant-Induced Irritant Contact Dermatitis through IL-1β‒Mediated Neutrophil Accumulation

Surfactant-induced cumulative irritant contact dermatitis (ICD) is a common and clinically important skin disorder. CCL2 is known to mediate inflammation after tissue damage in various organs. Thus, we investigated whether and how CCL2 contributes to the development of murine cumulative ICD induced by a common surfactant, SDS. Wild-type mice treated topically with SDS for 6 consecutive days developed skin inflammation that recapitulated the features of human cumulative ICD, including barrier disruption, epidermal thickening, and neutrophil accumulation. CCL2 was upregulated in SDS-treated skin, and local CCL2 blockade attenuated SDS-induced ICD. SDS-induced ICD and neutrophil accumulation were also attenuated in mice deficient in CCR2, the receptor for CCL2. Neutrophil depletion alleviated SDS-induced ICD, suggesting that impaired neutrophil accumulation was responsible for the amelioration of ICD in CCR2-deficient mice. In RNA-sequencing analyses of SDS-treated skin, the expression levels of Il1b in Ccr2-deficient mice were highly downregulated compared with those in wild-type mice. Furthermore, the intradermal administration of IL-1β in the SDS-treated skin of CCR2-deficient mice restored the local accumulation of neutrophils and the development of ICD. Collectively, our results suggest that CCL2‒CCR2 signaling in the skin critically promotes the development of SDS-induced ICD by inducing IL-1β expression for neutrophil accumulation.

Putative Immunological Functions of Inducible Skin-Associated Lymphoid Tissue in the Context of Mucosa-Associated Lymphoid Tissue

Acquired immunity is orchestrated in various lymphoid organs, including bone marrow, thymus, spleen, and lymph nodes in humans. However, mucosa-associated lymphoid tissue (MALT) is evolutionally known to be emerged in the oldest vertebrates as an immunological tissue for acquired immunity, much earlier than the advent of lymph nodes which appeared in endotherms. Furthermore, the lymphocytes which developed in MALT are known to circulate within the limited anatomical areas. Thus, MALT is comprehended as not the structure but the immune network dedicated to local immunity. As for the skin, skin-associated lymphoid tissue (SALT) was previously postulated; however, its existence has not been proven. Our group recently showed that aggregations of dendritic cells, M2 macrophages, and high endothelial venules (HEVs) are essential components to activate effector T cells in the murine contact hypersensitivity model and termed it as inducible SALT (iSALT) since it was a transient entity that serves for acquired immunity of the skin. Furthermore, in various human skin diseases, we reported that the ectopic formation of lymphoid follicles that immunohistochemically analogous to MALT and regarded them as human counterparts of iSALT. These data raised the possibility that SALT can exist as an inducible form, namely iSALT, which shares the biological significance of MALT. In this article, we revisit the evolution of immunological organs and the related components among vertebrates to discuss the conserved functions of MALT. Furthermore, we also discuss the putative characteristics and functions of iSALT in the context of the MALT concept.

Refractory serum immunoglobulin M elevation during anti-interleukin (IL)-1- or IL-6-targeted treatment in four patients with Schnitzler syndrome

Schnitzler syndrome is characterized by chronic urticarial rash, neutrophilic dermal infiltrate, recurrent fever, bone pain, elevated C-reactive protein, and neutrophilic leukocytosis. The pathophysiology of Schnitzler syndrome is unknown, but it is considered to be an acquired form of an autoinflammatory disease because of the resemblance to clinical phenotypes of cryopyrin-associated periodic syndrome, in which a gain-of-function mutation in NLRP3 causes overexpression of interleukin (IL)-1β. Schnitzler syndrome is generally accompanied by a monoclonal immunoglobulin (Ig)M gammopathy with a long-term risk of lymphoproliferation that is possibly associated with an MYD88 mutation. Herein, we present the following four patients with Schnitzler syndrome: a 63-year-old woman; a 65-year-old man; a 43-year-old woman; and a 63-year-old woman. Each patient fulfilled the Strasbourg diagnostic criteria, but none of the patients had any mutation in NLRP3 or MYD88 detected in their peripheral blood. Although approved treatment options for Schnitzler syndrome are lacking, our patients were treated with IL-1-targeted therapy (anakinra or canakinumab) or anti-IL-6 (tocilizumab). The acute inflammatory clinical manifestations improved completely with canakinumab and partially with anakinra and tocilizumab, but the serum IgM levels were gradually increased in all patients, even during treatment. To determine whether treatment with anti-IL-1β or IL-6 prevents conversion to a hematopoietic disorder, further collection of cases and long-term follow-up will be needed.

Longitudinal association between polypharmacy and development of pruritus: a Nationwide Cohort Study in a Japanese Population

BACKGROUND

Although polypharmacy is known to cause side-effects due to drug-drug interactions, dermatological symptoms triggered by polypharmacy are not fully addressed.

OBJECTIVE

To investigate whether polypharmacy is associated with the risk of pruritus.

METHOD

A cohort study was performed to examine cross-sectional and longitudinal relationships between polypharmacy and pruritus in a general population. Data were collected from the Norm Study conducted in 2016 and 2017, which is a nationwide survey based on a self-administered questionnaire with Japanese representative participants aged 16-84 years. Presence of polypharmacy which was defined as concurrent use of ≥5 prescribed drugs. Primary outcomes were the presence of severe pruritus at baseline for the cross-sectional analysis and the development of severe pruritus after one year for the longitudinal analysis. Multivariable modified Poisson regression analyses were performed to estimate risk ratios (RRs) and 95% confidence intervals (95%CIs) with adjustment for potential confounders (age, gender, smoking habits, drinking habits, depressive symptoms, moderate activities based on IPAQ score and presence of 11 comorbid conditions including skin disease).

RESULTS

The study included 3126 participants (mean age, 48.7 years); nearly half (49.8%) were male. In all, 332 participants (10.3%) had polypharmacy in the cross-sectional analysis. Participants with polypharmacy were more likely to present with severe pruritus at baseline than those who were not using drugs (adjusted RR = 1.52 [95%CI 1.15-2.01, P = 0.003]). The longitudinal analysis (n = 1803) was limited to those without severe pruritus at baseline; participants with polypharmacy at baseline were more likely to develop severe pruritus after a one-year follow-up period than those not using drugs (adjusted RR = 1.46 [95%CI 1.14-1.87, P = 0.002]).

CONCLUSION

Polypharmacy was associated with the presence of pruritus at baseline and may predict the future risk of developing pruritus.

Analysis of possible structures of inducible skin-associated lymphoid tissue in lupus erythematosus profundus

Lupus erythematosus profundus (LEP) is a variant of lupus erythematosus, involving the deep dermis and subcutaneous fat. LEP is characterized by the presence of lymphoid follicles (LF) and germinal centers (GC). However, it remains unknown whether these lymphoid structures correspond to the lymphoid tissues such as cutaneous tertiary lymphoid organs (TLO). Previously, we identified dynamically orchestrated cellular elements in murine contact dermatitis that resembled lymphoid structures, which we termed inducible skin-associated lymphoid tissues (iSALT). We subsequently reported structures analogous to iSALT in human secondary syphilis, suggesting that iSALT can also exist in humans. Here, we studied ectopic lymphoid tissues in the lesions of LEP by immunohistochemistry and compared their characteristics with those of TLO. We demonstrated that LF of LEP were composed of B-cell follicles intermingled with CXCL13-expressing cells, distinct aggregations of T cells, and some blood vessels expressing peripheral node addressin. These findings indicate that LF of LEP can be considered as a type of iSALT.

Extraocular sebaceous carcinoma accompanied by invasive squamous cell carcinoma: The first case report and consideration of histogenesis

A 61-year-old man presented with a dome-shaped nodule, 1.2 cm in size, with a central crater covered by keratinous material near the left lateral malleolus. Histological findings demonstrated a basophilic circular cone in the center, surrounded and sharply demarcated by a broad eosinophilic area. The central conical mass was composed mainly of atypical basaloid cells intermingled with scattered atypical sebaceous cells with scalloped nuclei and microvesicular cytoplasms, suggesting sebaceous carcinoma. The peripheral area consisted of atypical keratinizing squamoid cells without sebaceous cells, suggesting invasive squamous cell carcinoma. Atypical sebaceous cells were positive for adipophilin. Atypical basaloid cells were positive for 34βE12 and CAM5.2. Peripheral squamoid cells were positive for 34βB4 and 34βE12 throughout, and were positive for LHP1 in the superficial layer. We herein describe the first case of extraocular sebaceous carcinoma accompanied by invasive squamous cell carcinoma, which might have arisen from biphasic differentiation of cancer stem cells.

Analysis of lymphoid tissue markers in angiomatoid fibrous histiocytoma

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue neoplasm of uncertain differentiation. AFH is characterized by nodular distribution of ovoid and spindle cells with blood-filled cystic cavities. It is circumscribed by thick fibrous pseudo-capsule and a surrounding dense lympho-plasmacytic infiltration encompassing germinal centers. In this study, we analyzed the structure of AFH with immunohistochemistry using markers for lymphoid organogenesis.

The tumor was a circumscribed pyriform mass, composed of histiocytoid and spindle cells. The top part of the mass encompassed cribriform vasculature, which was positive for CD31, a marker for blood endothelial cells (BECs). This BEC-dominant area contained numerous lymphoid, histiocytoid, or fibroblastoid cells, which expressed CD4 (but not CD3), CD31, CXCL13, SDF-1 (CXCL12), and receptor for LTβ (LTβR). The peripheral lymph node address in (PNAd), a marker for high endothelial venules (HEVs), was positive in some vessels, where T and B cells were clustered. The bottom part of the mass was occupied with polygonal cells expressing podolanin, a marker for lymphatic epithelial cells (LECs). The whole mass was encapsulated with CD10+ fibroblast-like cells and surrounded by organized lymphoid infiltration containing T cell areas and B cell follicles with germinal centers.

Our analysis illustrates a case of AFH composed of BEC- and LEC-dominant compartments. The well-organized peritumoral lymphoid infiltration indicated that AFH may produce an environment suitable for inducing inducible skin associated lymphoid tissue (iSALT).

Spindle cell squamous cell carcinoma arising in Bowen's disease: Case report and review of the published work

A 79-year-old Japanese woman presented with an ulcerated, brown-red nodule in the center of a sharply demarcated, tan-brown plaque situated on the left side of her right breast. Histologically, the plaque demonstrated an acanthosis with an intraepidermal epithelioma of Borst-Jadassohn. Small oval nests of bland-appearing basophilic cells in the periphery gradually enlarged into nests of various sizes and irregular shapes, composed of densely cohesive, atypical basophilic cells above the central nodule. The atypical keratinocytes shifted to atypical spindle cells beneath the acanthotic epidermis, penetrating deep into the subcutaneous tissue. In addition to vimentin and p63, the spindle cells were positive for several cytokeratin (CK) markers, including AE1/AE3, 34βE12 and CK5/6, which showed more intense signals closer to the epidermis. Basophilic cells in the clonal nests were positive for p63, AE1/AE3, 34βE12 and CK5/6. The MIB-1 index was estimated at approximately 40-50% in both the bland-appearing and the atypical basophilic cells. We describe the first case of spindle cell squamous cell carcinoma arising in an intraepidermal epithelioma expressed by clonal Bowen's disease, which was difficult to differentiate from clonal seborrheic keratosis.

4-Fragment Gateway cloning format for MosSCI-compatible vectors integrating Promoterome and 3'UTRome libraries of Caenorhabditis elegans

The technique of Mos1-mediated Single Copy Insertion (MosSCI) now has become the essential technique which facilitates transgenic experiments for Caenohabditis elegans (C. elegans). Gateway system which is adopted to MosSCI-compatible vectors offers an advantage of simultaneous cloning with entry vectors cloned in the Gateway system format. On the other hand, the format for MosSCI-compatible vectors restricts flexibility in designing the vectors to only 3-fragment integration. Thus, construct of complex transgene such as the expression vector for translational gene fusion is tedious work even with Gateway system. We have developed the new recombination format called LeGaSCI (Library-enhanced Gateway for MosSCI) to expand the conventional 3-fragment to 4-fragment format which still retains the capacity to accept Promoterome and 3'UTRome libraries of C. elegans. In the new recombination format, 2 different Gateway format were combined. Cloning reaction for the tissue-specific expression vector of GFP-tagged protein with 3'UTR successfully occurred without any expected insertion, deletion or frame-shift mutation. Moreover, The MosSCI transgenic line was successfully generated with the construct. Collectively, we established the new Gateway system format which allows us to assemble 4-fragment insertion with the widest variety of entry clone vectors from C. elegans libraries.

Palmoplantar keratosis in oculodentodigital dysplasia with a GJA1 point mutation out of the C-terminal region of connexin 43

Gap junction proteins are composed of 21 genes of the connexin (Cx) family. They play important roles in cell-cell contact by exchange of small molecules through hemichannels. Hence, mutations of Cx family genes affect various tissues of a body. The mutation of the GJA1 gene, which codes Cx43, causes oculodentodigital dysplasia (ODDD), commonly in an autosomal dominant manner with phenotypic variability. It has been believed that gene mutations causing truncation of the Cx43 C-terminus is necessary and sufficient for palmoplantar keratosis (PPK) development in ODDD patients. Here, we report a case of an ODDD patient developing PPK with a GJA1 gene mutation (c.412G>A/p.Gly138Ser), which was previously reported in a case of ODDD without PPK and expected not to result in C-terminal truncation of Cx43. This case suggests not only C-terminal truncation, but also that a point mutation in the cytoplasmic region of Cx43 can cause PPK in ODDD patients.

Differential and common DNA repair pathways for topoisomerase I- and II-targeted drugs in a genetic DT40 repair cell screen panel

Clinical topoisomerase I (Top1) and II (Top2) inhibitors trap topoisomerases on DNA, thereby inducing protein-linked DNA breaks. Cancer cells resist the drugs by removing topoisomerase-DNA complexes, and repairing the drug-induced DNA double-strand breaks (DSB) by homologous recombination and nonhomologous end joining (NHEJ). Because numerous enzymes and cofactors are involved in the removal of the topoisomerase-DNA complexes and DSB repair, it has been challenging to comprehensively analyze the relative contribution of multiple genetic pathways in vertebrate cells. Comprehending the relative contribution of individual repair factors would give insights into the lesions induced by the inhibitors and genetic determinants of response. Ultimately, this information would be useful to target specific pathways to augment the therapeutic activity of topoisomerase inhibitors. To this end, we put together 48 isogenic DT40 mutant cells deficient in DNA repair and generated one cell line deficient in autophagy (ATG5). Sensitivity profiles were established for three clinically relevant Top1 inhibitors (camptothecin and the indenoisoquinolines LMP400 and LMP776) and three Top2 inhibitors (etoposide, doxorubicin, and ICRF-193). Highly significant correlations were found among Top1 inhibitors as well as Top2 inhibitors, whereas the profiles of Top1 inhibitors were different from those of Top2 inhibitors. Most distinct repair pathways between Top1 and Top2 inhibitors include NHEJ, TDP1, TDP2, PARP1, and Fanconi Anemia genes, whereas homologous recombination seems relevant especially for Top1 and, to a lesser extent, for Top2 inhibitors. We also found and discuss differential pathways among Top1 inhibitors and Top2 inhibitors.

GEMIN2 promotes accumulation of RAD51 at double-strand breaks in homologous recombination

RAD51 is a key factor in homologous recombination (HR) and plays an essential role in cellular proliferation by repairing DNA damage during replication. The assembly of RAD51 at DNA damage is strictly controlled by RAD51 mediators, including BRCA1 and BRCA2. We found that human RAD51 directly binds GEMIN2/SIP1, a protein involved in spliceosome biogenesis. Biochemical analyses indicated that GEMIN2 enhances the RAD51–DNA complex formation by inhibiting RAD51 dissociation from DNA, and thereby stimulates RAD51-mediated homologous pairing. GEMIN2 also enhanced the RAD51-mediated strand exchange, when RPA was pre-bound to ssDNA before the addition of RAD51. To analyze the function of GEMIN2, we depleted GEMIN2 in the chicken DT40 line and in human cells. The loss of GEMIN2 reduced HR efficiency and resulted in a significant decrease in the number of RAD51 subnuclear foci, as observed in cells deficient in BRCA1 and BRCA2. These observations and our biochemical analyses reveal that GEMIN2 regulates HR as a novel RAD51 mediator.

Crystal structure of human REV7 in complex with a human REV3 fragment and structural implication of the interaction between DNA polymerase zeta and REV1

DNA polymerase zeta (Polzeta) is an error-prone DNA polymerase involved in translesion DNA synthesis. Polzeta consists of two subunits: the catalytic REV3, which belongs to B family DNA polymerase, and the noncatalytic REV7. REV7 also interacts with REV1 polymerase, which is an error-prone Y family DNA polymerase and is also involved in translesion DNA synthesis. Cells deficient in one of the three REV proteins and those deficient in all three proteins show similar phenotype, indicating the functional collaboration of the three REV proteins. REV7 interacts with both REV3 and REV1 polymerases, but the structure of REV7 or REV3, as well as the structural and functional basis of the REV1-REV7 and REV3-REV7 interactions, remains unknown. Here we show the first crystal structure of human REV7 in complex with a fragment of human REV3 polymerase (residues 1847-1898) and reveal the mechanism underlying REV7-REV3 interaction. The structure indicates that the interaction between REV7 and REV3 creates a structural interface for REV1 binding. Furthermore, we show that the REV7-mediated interactions are responsible for DNA damage tolerance. Our results highlight the function of REV7 as an adapter protein to recruit Polzeta to a lesion site. REV7 is alternatively called MAD2B or MAD2L2 and also involved in various cellular functions such as signal transduction and cell cycle regulation. Our results will provide a general structural basis for understanding the REV7 interaction.

Collaborative action of Brca1 and CtIP in elimination of covalent modifications from double-strand breaks to facilitate subsequent break repair

Topoisomerase inhibitors such as camptothecin and etoposide are used as anti-cancer drugs and induce double-strand breaks (DSBs) in genomic DNA in cycling cells. These DSBs are often covalently bound with polypeptides at the 3′ and 5′ ends. Such modifications must be eliminated before DSB repair can take place, but it remains elusive which nucleases are involved in this process. Previous studies show that CtIP plays a critical role in the generation of 3′ single-strand overhang at “clean” DSBs, thus initiating homologous recombination (HR)–dependent DSB repair. To analyze the function of CtIP in detail, we conditionally disrupted the CtIP gene in the chicken DT40 cell line. We found that CtIP is essential for cellular proliferation as well as for the formation of 3′ single-strand overhang, similar to what is observed in DT40 cells deficient in the Mre11/Rad50/Nbs1 complex. We also generated DT40 cell line harboring CtIP with an alanine substitution at residue Ser332, which is required for interaction with BRCA1. Although the resulting CtIP^{S332A/−/−} cells exhibited accumulation of RPA and Rad51 upon DNA damage, and were proficient in HR, they showed a marked hypersensitivity to camptothecin and etoposide in comparison with CtIP^+/−/− cells. Finally, CtIP^{S332A/−/−}BRCA1^−/− and CtIP^+/−/−BRCA1^−/− showed similar sensitivities to these reagents. Taken together, our data indicate that, in addition to its function in HR, CtIP plays a role in cellular tolerance to topoisomerase inhibitors. We propose that the BRCA1-CtIP complex plays a role in the nuclease-mediated elimination of oligonucleotides covalently bound to polypeptides from DSBs, thereby facilitating subsequent DSB repair.

Induction of double-strand breaks (DSBs) in chromosomal DNA effectively activates a program of cellular suicide and is widely used for chemotherapy on malignant cancer cells. Cells resist such therapies by quickly repairing the DSBs. Repair is carried out by two major DSB repair pathways, homologous recombination (HR) and nonhomologous end-joining. However, these pathways cannot join DSBs if their ends are chemically modified, as seen in the DSB ends that would arise after the prolonged treatment of the cells with topoisomerase inhibitors such as camptothecin and etoposide. These anti-cancer drugs can produce the polypeptides covalently attached to the 3′ or 5′ end of DSBs. It remains elusive which enzymes eliminate these chemical modifications prior to repair. We here show evidence that the BRCA1-CtIP complex plays a role in eliminating this chemical modification, thereby facilitating subsequent DSB repair. Thus, BRCA1 and CtIP have dual functions: their previously documented roles in HR and this newly identified function. This study contributes to our ability to predict the effectiveness of chemotherapeutic agents prior to their selection by evaluating the activity of individual repair factors. Accurate prediction is crucial, because chemotherapeutic agents that cause DNA damage have such strong side effects.

A novel approach using DNA-repair-deficient chicken DT40 cell lines for screening and characterizing the genotoxicity of environmental contaminants

BACKGROUND

Many bacterial or mammalian cell-based test systems, such as the Ames test, chromosomal aberration assays, or gene mutation assays, are commonly used in developed countries to detect the genotoxicity of industrial chemicals. However, the specificity is generally limited and the sensitivity is not sufficiently high. In addition, most assays cannot provide information on mechanisms of genotoxicity of a given chemical.

OBJECTIVES

We aimed to establish a sensitive and fast screening method that is also capable of characterizing mechanisms of genotoxicity.

METHODS

We developed a novel bioassay employing gene-disrupted clones of the chicken DT40 B-lymphocyte line, which are designed to be deficient in several specific DNA repair pathways. Genotoxic chemicals can delay cellular proliferation in DNA-repair-deficient clones more significantly than in wild-type cells by interfering with DNA replication, thereby inducing DNA damage. In addition, we verified the validity of this assay by analyzing the genotoxicity of gamma-rays, ultraviolet (UV) light, and sodium metaarsenite (NaAsO(2)). We also characterized DNA lesions induced by NaAsO(2).

RESULTS

Genotoxicity of given stressors was successfully screened based on a comparison of proliferation kinetics between wild-type and DNA-repair-deficient mutants in 48 hr. We also found that NaAsO(2) apparently induces at least two types of damage: chromosomal breaks and UV photoproduct-like DNA lesions.

CONCLUSION

This bioassay is a reliable and sensitive screening tool for environmental mutagens as well as for further characterizing the nature of detected genotoxicity.

Ebselen attenuates oxidative stress-induced apoptosis via the inhibition of the c-Jun N-terminal kinase and activator protein-1 signalling pathway in PC12 cells

1: Ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one) is a selenoorganic compound exhibiting both glutathione peroxidase activity and antioxidant activity. Although it has been reported that ebselen is effective for oxidative stress-induced neuronal damage both in vivo and clinically, the precise mechanisms of the efficacy have not yet been elucidated. Thus, we hypothesized that ebselen may affect reactive oxygen species-induced mitogen-activated protein (MAP) kinase activation in cultured PC12 cells. 2: Our findings showed that hydrogen peroxide (H(2)O(2)) stimulated rapid and significant activation of extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK) and p38 in PC12 cells, which is a model of catecholamine-containing neurons. 3: H(2)O(2)-induced JNK activation was inhibited by ebselen, whereas ERK1/2 and p38 activation by H(2)O(2) were not affected by ebselen. 4: Inhibition by ebselen of H(2)O(2)-induced hydroxyl radical generation in PC12 cells was observed using electron paramagnetic resonance measurements. Ebselen also inhibited H(2)O(2)-induced increases in DNA binding activity of activator protein-1 (AP-1), a downstream transcription factor of JNK, composed of the c-Jun homo/heterodimer. 5: Finally, pretreatment of cells with ebselen resulted in a significant recovery from cell death including apoptosis by H(2)O(2) in PC12 cells. 6 These findings suggest that ebselen attenuates oxidative stress-induced neuronal cell death through the inhibition of the JNK and AP-1 signalling pathway. Thus, inhibition of JNK by ebselen may imply its usefulness for treatment of ischaemic cerebral diseases relevant to neuronal cell death.

[Myocardial imaging in acute myocardial infarction using beta-methyl-p-(123I)-iodophenylpentadecanoic acid: comparison with 201Tl imaging and wall motion]

Myocardial imaging using beta-methyl-p-(123I)-iodophenylpentadecanoic acid (BMIPP) was performed in 11 patients with acute myocardial infarction. The left ventricular images were divided into 12 segments, and myocardial imagings with BMIPP were compared with coronary angiography (CAG), thallium-201 myocardial scintigraphy (TL) and wall motion obtained by two-dimensional echocardiography (WM). When the culprit lesion was at the proximal point of the left anterior descending artery (LAD), all segments showed depressed uptake. In 3 cases with single vessel disease of the LAD, inferior wall of the basis showed reduced uptake of BMIPP despite the location of the culprit lesion. In cases with discordant uptake between the two tracers, BMIPP frequently showed more severely depressed uptake than TL in the subacute phase, although the uptake of BMIPP correlated with that of TL (tau = 0.82, p less than 0.001). In such cases, the discordance was related to the improvement in WM from the acute phase to the convalescent phase. BMIPP uptake correlated with WM in the subacute phase (tau = 0.50, p less than 0.001). BMIPP showed more severely depressed uptake while WM showed mild asynergy in most cases in which discordance was found between the BMIPP and WM findings. However, there was no correlation between the change in WM from the acute to subacute phases, or the uptakes of BMIPP and TL alone. We concluded that the myocardial condition can be evaluated in detail in acute myocardial infarction by comparing the findings of BMIPP with those of TL and WM.

[Indication for coronary revascularization in patients without redistribution on 201Tl myocardial scintigraphy]

To determine the indication for coronary revascularization (A-C bypass and PTCA), we performed thallium(Tl)-201 scintigraphy and contrast left ventriculography (LVG) in 25 cases who had A-C bypass surgery and 22 cases who had PTCA. The Tl uptake in the delayed image (Tl score = normal: 3, mild hypoperfusion: 2, severe hypoperfusion: 1, defect: 0), the presence of redistribution, and regional wall motion by LVG (LVG score = normal: 3, reduced: 2, none: 1, dyskinesis: 0), were compared with each other before and after revascularization. Sensitivity, specificity and accuracy of myocardial viability as evaluated by each index were; the presence of redistribution; 96%, 35%, and 60%; Tl score much greater than 2; 83%, 33%, and 66%; Tl score much greater than 1; 81%, 75%, and 81%; LVG score much greater than 2; 80%, 29%, and 63%; and LVG score much greater than 1; 79%, 33%, and 74%; respectively. It was difficult to evaluate the myocardial viability only by the presence of redistribution. However, any case with redistribution was a prime candidate for coronary revascularization. The Tl score much greater than 1 was the most reliable indication using the individual index. Although the diagnostic accuracies of the Tl and LVG scores were superior to the presence of redistribution, there was no individual index of myocardial viability common to all cases. If there were clinical necessity and angiographic indication, coronary revascularization could be tried in all cases except those whose Tl and LVG scores were both 0. In conclusion, myocardial viability can be evaluated scintigraphically only by the delayed image and by the presence of redistribution. As a conventional indication for coronary revascularization, the Tl score is relatively useful for predicting improvement after revascularization.

Baroreceptor reflex to neck suction and its modification by diltiazem in man

The carotid sinus baroreceptor reflex was studied in 15 healthy young men by a variable pressure neck suction chamber. Neck suction produced a reduction in blood pressure and an increase in RR interval, which were augmented by an increase of stimuli. Both responses occurred promptly and were attenuated with time. The reproducibility of the response was examined in 6 subjects. There were no differences in either hypotensive or bradycardiac responses between 2 runs separated by 1 hour, indicating good short-term reproducibility. In a long-term reproducibility study involving 2 runs separated by 2 weeks, hypotensive responses showed similar changes, whereas bradycardiac responses showed a wide variation. Based on this good reproducibility of responses, the effects of diltiazem on baroreflex function were studied in 9 men. Following the administration of diltiazem (20 mg, P.O.), the hypotensive responses to neck suction stimuli were significantly augmented compared to preadministration responses. On the other hand, diltiazem did not have a significant influence on heart rate responses. Thus, the present study shows that the neck chamber method is a feasible approach to studying the influence of given interventions on baroreflex function and demonstrates an enhancement of baroreflex-mediated hypotension by diltiazem.