Regulation of CD23 expression by Notch2 in B-cell chronic lymphocytic leukemia

The association between the level of specific IgE to molecular components of mites and the expression of CD23 molecule on B lymphocytes in atopic dermatitis patients treated or not treated with dupilumab-Pilot study

BACKGROUND

The CD23 molecule has an effect on the regulation of IgE synthesis, either by stimulation or inhibition. It is not yet known whether the expression of CD23 on B lymphocytes is related to the level of allergen-specific IgE antibodies in patients with atopic dermatitis.

AIM

The aim of this pilot study was to evaluate the association between the expression of CD23 molecule on B cells and on their subsets (memory, naive, switched, non-switched, and total B lymphocytes) and the level of specific IgE to molecular components of mites in atopic dermatitis patients (with and without dupilumab therapy).

METHODS

Forty-five patients suffering from atopic dermatitis were included: 32 patients without dupilumab treatment (10 men, 22 women, average age 35 years), 13 patients with dupilumab treatment (7 men, 6 women, average age 43.4 years) and 30 subjects as a control group (10 men, 20 women, average age 44.7 years). The serum level of the specific IgE was measured using the components resolved diagnostic microarray-based specific IgE detection assay ALEX2 Allergy Xplorer. In all included patients, the expression of CD23 molecule on B lymphocytes was evaluated with flow cytometry using monoclonal antibodies. For the statistical analysis of the association between expression of CD23 molecule on B lymphocytes and the level of specific IgE to molecular components of mites, we used non-parametric Kruskal-Wallis one-factor analysis of variance with post-hoc by Dunn's test with Bonferroni modification and the Spearman's rank correlation coefficient; for coefficients higher than 0.41, we report R2 (%, percent of Variation Explained).

RESULTS

The association between the expression of CD23 molecule on B cells and the level of specific IgE to molecular components of mites was confirmed only in patients with dupilumab therapy. In these patients, the highest association was confirmed between the level of specific IgE to Der p 20 and expression of CD23 on switched B lymphocytes (in 48.9%). In patients without dupilumab, the association between the level of specific IgE to molecular components of mites and the expression of CD23 on B cells and on their subsets is low.

CONCLUSION

Further research is needed to fully understand the underlying mechanism of this phenomenon and its implications for the treatment of atopic dermatitis.

RNF144B stimulates the proliferation and inhibits the apoptosis of human spermatogonial stem cells via the FCER2/NOTCH2/HES1 pathway and its abnormality is associated with azoospermia

Studies on gene regulation and signaling transduction pathways of human spermatogonial stem cells (SSCs) are of the utmost significance for unveiling molecular mechanisms underlying human spermatogenesis and gene therapy of male infertility. We have demonstrated, for the first time, that RNF144B stimulated cell proliferation and inhibited the apoptosis of human SSCs. The target of RNF144B was identified as FCER2 by RNA sequencing. We revealed that RNF144B interacted with FCER2 by immunoprecipitation. Consistently, overexpression of FCER2 reversed the phenotype of proliferation and apoptosis of human SSCs caused by RNF144B knockdown. Interestingly, FCER2 pulled down N2ICD (NOTCH2 intracellular domain), while N2ICD could bind to FCER2 in human SSCs. The levels of NOTCH2, FCER2, HES1, and HEY1 were reduced by RNF144B siRNA in human SSCs. Significantly, RNF144B was expressed at a lower level in nonobstructive azoospermia (NOA) patients than in the obstructive azoospermia (OA) patients with normal spermatogenesis, and 52 patients with heterozygous mutations of RNF144B were detected in 1,000 NOA patients. These results implicate that RNF144B promotes the proliferation of human SSCs and suppresses their apoptosis via the FCER2/NOTCH2/HES1 pathway and that the abnormality of RNF144B is associated with spermatogenesis failure. This study thus provides novel molecular mechanisms regulating the fate determinations of human SSCs, and it offers new biomarkers for the diagnosis and treatment of male infertility.

The role of CD23 in the regulation of allergic responses

IgE, the key molecule in atopy has been shown to bind two receptors, FcεRI, the high‐affinity receptor, and FcεRII (CD23), binding IgE with lower affinity. Whereas cross‐linking of IgE on FcεRI expressed by mast cells and basophils triggers the allergic reaction, binding of IgE to CD23 on B cells plays an important role in both IgE regulation and presentation. Furthermore, IgE‐immune complexes (IgE‐ICs) bound by B cells enhance antibody and T cell responses in mice and humans. However, the mechanisms that regulate the targeting of the two receptors and the respective function of the two pathways in inflammation or homeostasis are still a matter of debate. Here, we focus on CD23 and discuss several mechanisms related to IgE binding, as well as the impact of the IgE/antigen‐binding on different immune cells expressing CD23. One recent paper has shown that free IgE preferentially binds to FcεRI whereas IgE‐ICs are preferentially captured by CD23. Binding of IgE‐ICs to CD23 on B cells can, on one hand, regulate serum IgE and prevent effector cell activation and on the other hand facilitate antigen presentation by delivering the antigen to dendritic cells. These data argue for a multifunctional role of CD23 for modulating IgE serum levels and immune responses.

IgE low affinity receptor (CD23) expression, Plasmodium falciparum specific IgE and tumor necrosis factor-alpha production in Thai uncomplicated and severe falciparum malaria patients

Previous studies have suggested that Plasmodium falciparum (P. falciparum) specific IgE in the form of immune complexes crosslinking the low-affinity receptor (CD23) on monocyte results in tumor necrosis factor (TNF)-α and nitric oxide (NO) production. However, the roles of these parameters in severity and immune protection are still unclear. This study aimed to determine the association between CD23 expression on monocytes, plasma soluble CD23 (sCD23), total IgE, malaria-specific IgE and IgG, and TNF-α levels in P. falciparum infected patients. We evaluated 64 uncomplicated (UC) and 25 severe patients (S), admitted at the Hospital for Tropical Diseases, Mahidol University, and 34 healthy controls (C) enrolled in 2001. Flow cytometry and enzyme linked immunosorbent assays (ELISA) demonstrated that trends of the CD23 expression, levels of sCD23 and specific IgE were higher in the S group as compared to those in the UC and C groups. Plasma levels of P. falciparum specific IgE in the UC (p=0.011) and S groups (p=0.025) were significantly higher than those in C group. In contrast the TNF-α levels tended to be higher in the UC than those in the S (p=0.343) and significantly higher than those in C (p=0.004) groups. The specific IgG levels in UC were significantly higher than those in S and C (p<0.001) groups. At admission, a strong significant negative correlation was found between specific IgG and sCD23 (r=-0.762, p=0.028), and TNF-α and IgE-IgG complexes (r=-0.715, p=0.002). Significant positive correlations between levels of specific IgE and TNF-α (r=0.575, p=0.010); and sCD23 (r=0.597, p=0.000) were also observed. In conclusion, our data suggest that CD23 expression and malaria-specific IgE levels may be involved in the severity of the disease while TNF-α and the malaria-specific IgG may correlate with protection against falciparum malaria.

Getting the message direct manipulation of host mRNA accumulation during gammaherpesvirus lytic infection

The Gammaherpesvirinae subfamily of herpesviruses comprises lymphotropic viruses, including the oncogenic human pathogens Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus. During lytic infection, gammaherpesviruses manipulate host gene expression to optimize the cellular environment for viral replication and to evade the immune response. Additionally, although a lytically infected cell will itself be killed in the process of viral replication, lytic infection can contribute to pathogenesis by inducing the secretion of paracrine factors with functions in cell survival and proliferation, and angiogenesis. The mechanisms by which these viruses manipulate host gene expression are varied and target the accumulation of cellular mRNAs and their translation, signaling pathways, and protein stability. Here, we discuss how gammaherpesviral proteins directly influence host mRNA biogenesis and stability, either selectively or globally, in order to fine-tune the cellular environment to the advantage of the virus. Appreciation of the mechanisms by which these viruses interface with and adapt normal cellular processes continues to inform our understanding of gammaherpesviral biology and the regulation of mRNA accumulation and turnover in our own cells.

Notch signalling in T-cell lymphoblastic leukaemia/lymphoma and other haematological malignancies

Notch receptors participate in a highly conserved signalling pathway that regulates normal development and tissue homeostasis in a context- and dose-dependent manner. Deregulated Notch signalling has been implicated in many diseases, but the clearest example of a pathogenic role is found in T-cell lymphoblastic leukaemia/lymphoma (T-LL), in which the majority of human and murine tumours have acquired mutations that lead to aberrant increases in Notch1 signalling. Remarkably, it appears that the selective pressure for Notch mutations is virtually unique among cancers to T-LL, presumably reflecting a special context-dependent role for Notch in normal T-cell progenitors. Nevertheless, there are some recent reports suggesting that Notch signalling has subtle, yet important roles in other forms of haematological malignancy as well. Here, we review the role of Notch signalling in various blood cancers, focusing on T-LL with an eye towards targeted therapeutics.

NOTCH2 links protein kinase C delta to the expression of CD23 in chronic lymphocytic leukaemia (CLL) cells

One characteristic of chronic lymphocytic leukaemia (CLL) lymphocytes is high expression of CD23, which has previously been identified as a downstream target for NOTCH2 signalling. The mechanisms regulating NOTCH2-dependent CD23 expression, however, are largely unknown. This study showed that peripheral CLL cells overexpressed transcriptionally active NOTCH2 (N2(IC)), irrespective of their prognostic marker profile. When placed in culture, NOTCH2 activity was spontaneously decreased in 25 out of 31 CLL cases (81%) within 24 h. DNA-bound N2(IC) complexes could be maintained by the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) or by gamma-interferon (IFN-gamma), two CLL characteristic inducers of CD23 expression. Inhibition of PKC-delta by RNA interference or by rottlerin antagonised PMA-induced NOTCH2 activation and also suppressed NOTCH2 activity in CLL cases with constitutively activated NOTCH2 signalling. In 23 out of 29 CLL cases tested (79%), DNA-bound N2(IC) complexes were found to be resistant to the gamma-secretase inhibitor (GSI) DAPT, suggesting that GSIs will be only effective in a subset of CLL cases. These data suggest that deregulation of NOTCH2 signalling is critically involved in maintaining the malignant phenotype of CLL lymphocytes and point to a link between PKC-delta and NOTCH2 signalling in the leukemic cells.

Enhancing transduction of the liver by adeno-associated viral vectors

A number of distinct factors acting at different stages of the adeno-associated virus vector (AAV)-mediated gene transfer process were found to influence murine hepatocyte transduction. Foremost among these was the viral capsid protein. Self-complementary (sc) AAV pseudotyped with capsid from serotype 8 or rh.10 mediated fourfold greater hepatocyte transduction for a given vector dose when compared with vector packaged with AAV7 capsid. An almost linear relationship between vector dose and transgene expression was noted for all serotypes with vector doses as low as 1 x 10(7) vg per mouse (4 x 10(8) vg kg(-1)) mediating therapeutic levels of human FIX (hFIX) expression. Gender significantly influenced scAAV-mediated transgene expression, with twofold higher levels of expression observed in male compared with female mice. Pretreatment of mice with the proteasome inhibitor bortezomib increased scAAV-mediated hFIX expression from 4+/-0.6 to 9+/-2 microg ml(-1) in female mice, although the effect of this agent was less profound in males. Exposure of mice to adenovirus 10-20 weeks after gene transfer with AAV vectors augmented AAV transgene expression twofold by increasing the level of proviral mRNA. Hence, optimization of individual steps in the AAV gene transfer process can further enhance the potency of AAV-mediated transgene expression, thus increasing the probability of successful gene therapy.