Bcl10 mediates angiotensin II-induced cardiac damage and electrical remodeling

Angiotensin (Ang) II is a potent mediator of both hypertension and cardiac damage; however, the mechanisms by which this occur remain unclear. B-cell lymphoma/leukemia 10 (Bcl10) is a member of the CBM signalosome, which links Ang II and nuclear factor-κB signaling. We hypothesized that Bcl10 is pivotal in the pathogenesis of Ang II-induced cardiac damage. Ang II infusion in mice lacking Bcl10 resulted in reduced cardiac fibrosis, less cellular infiltration, and improved arrhythmogenic electric remodeling, despite a similar degree of hypertension or cardiac hypertrophy. Adoptive transfer of bone marrow (BM), whereby Bcl10 knockout or wildtype BM was transferred to their opposite genotype recipients, revealed the dual importance of Bcl10 within both cardiac and immune cells. Loss of Bcl10 in cardiac cells resulted in reduced expression of genes important for the adhesion and recruitment of immune cells. In vitro experiments demonstrated that adhesion of monocytes to Ang II-treated endothelial cells also required Bcl10. Additionally, Bcl10 deficiency in macrophages reduced their intrinsic migratory ability. To address the role of BM-derived fibroblasts in the formation of cardiac fibrosis, we explored whether Bcl10 is also important for the infiltration of BM-derived (myo)fibroblasts into the heart. The transfer of green fluorescent protein positive wildtype BM into Bcl10 knockout recipient mice revealed a reduced number of noncardiac (myo)fibroblasts compared with those wildtype recipients. Our results demonstrate the significant role of Bcl10 in multiple cell types important for the generation of Ang II-induced cardiac damage and electric remodeling and may provide a new avenue for therapeutic intervention.

Prorenin receptor is essential for podocyte autophagy and survival

The prorenin receptor (PRR) is highly expressed in podocytes, but its role in the maintenance of podocyte function is unknown. Here we generated podocyte-specific PRR-knockout mice and found that these animals died between 2 to 3 wk after birth. Within 14 d, PRR-knockout mice developed nephrotic syndrome, albuminuria with podocyte foot-process fusion, and cytoskeletal changes. Podocyte-specific PRR deletion also led to disturbed processing of multivesicular bodies and enrichment of autophagosomal (LC3) and lysosomal (LAMP2) markers, indicating a functional block in autophagosome-lysosome fusion and an overload of the proteasomal protein-degradation machinery. In vitro, PRR knockdown and pharmacologic blockade of vacuolar H(+)-ATPases, which associate with the PRR, increased vesicular pH, led to accumulation of LC3-positive and LAMP2-positive vesicles and altered the cytoskeleton. Taken together, these results suggest that the PRR is essential for podocyte function and survival by maintaining autophagy and protein-turnover machinery. Furthermore, PRR contributes to the control of lysosomal pH, which is important for podocyte survival and cytoskeletal integrity.

Induction of long-lived allergen-specific plasma cells by mucosal allergen challenge

BACKGROUND

Allergen-specific IgE antibodies are responsible for the pathogenesis of type I hypersensitivity. In patients with allergy, IgE titers can persist in the apparent absence of allergen for years. Seasonal allergen exposure triggers clinical symptoms and enhances allergen-specific IgE. Whether allergen-specific plasma cells originating from seasonal allergen exposures can survive and become long-lived is so far unclear.

OBJECTIVE

We analyzed the localization and lifetimes of allergen-specific IgE-secreting, IgA-secreting, and IgG(1)-secreting plasma cells after allergen inhalation in an ovalbumin-induced murine model of allergic asthma.

METHODS

Ovalbumin-specific IgG(1)-secreting, IgA-secreting, and IgE-secreting cells in lungs, spleen, and bone marrow were isolated and tested for antibody secretion by the ELISpot technique. Longevity of ovalbumin-specific plasma cells was determined by cyclophosphamide treatment, which depletes proliferating plasmablasts but leaves plasma cells untouched. Ovalbumin aerosol-induced infiltrates in lungs were localized by confocal microscopy.

RESULTS

Long-lived ovalbumin-specific plasma cells were generated by systemic sensitization and survived in bone marrow and spleen, maintaining systemic ovalbumin-specific titers of IgG, IgA, and IgE. On inhalation of ovalbumin-containing aerosol, sensitized mice developed airway inflammation and more ovalbumin-specific IgG(1)-secreting, IgA-secreting, and IgE-secreting cells in the lungs and in secondary lymphoid organs. These plasma cells joined the pool of ovalbumin-specific plasma cells in the bone marrow and became long-lived-that is, they are resistant to cyclophosphamide. Termination of ovalbumin inhalation depleted ovalbumin-specific plasma cells from the lungs, but they persisted in spleen and bone marrow.

CONCLUSION

Our results show that inhalation of aerosolized allergen generates long-lived, allergen-specific IgG(1)-secreting, IgA-secreting, and IgE-secreting plasma cells that survive cytostatic treatment.

Nerve growth factor and neurotrophin-3 mediate survival of pulmonary plasma cells during the allergic airway inflammation

Allergen-specific Abs play a pivotal role in the induction and maintenance of allergic airway inflammation. During secondary immune responses, plasma cell survival and Ab production is mediated by extrinsic factors provided by the local environment (survival niches). It is unknown whether neurotrophins, a characteristic marker of allergic airway inflammation, influence plasma cell survival in the lung. Using a mouse model of allergic asthma, we found that plasma cells from the lung and spleen are distinct subpopulations exhibiting differential expression patterns of neurotrophins and their receptors (Trks). In vitro, the nerve growth factor (NGF) and neurotrophin-3 (NT3) led to a dose-dependent increase in viability of isolated pulmonary plasma cells due to up-regulation of the antiapoptotic Bcl2 pathway. In parallel, the expression of transcription factors that stimulate the production of immunoglobulins (X-box binding protein 1 and NF-kappaB subunit RelA) was enhanced in plasma cells treated with NGF and NT3. These findings were supported in vivo. When the NGF pathway was blocked by intranasal application of a selective TrkA inhibitor, sensitized mice showed reduced numbers of pulmonary plasma cells and developed lower levels of allergen-specific and total serum IgE in response to OVA inhalation. This suggests that in the allergic airway inflammation, NGF/TrkA-mediated pulmonary IgE production contributes significantly to serum-IgE levels. We conclude that the neurotrophins NGF and NT3 act as survival factors for pulmonary plasma cells and thus are important regulators of the local Ab production in the allergic airway disease.