Staphylococcus aureus proteases trigger eosinophil-mediated skin inflammation.

Staphylococcus aureus skin colonization and eosinophil infiltration are associated with many inflammatory skin disorders, including atopic dermatitis, bullous pemphigoid, Netherton's syndrome, and prurigo nodularis. However, whether there is a relationship between S. aureus and eosinophils and how this interaction influences skin inflammation is largely undefined. We show in a preclinical mouse model that S. aureus epicutaneous exposure induced eosinophil-recruiting chemokines and eosinophil infiltration into the skin. Remarkably, we found that eosinophils had a comparable contribution to the skin inflammation as T cells, in a manner dependent on eosinophil-derived IL-17A and IL-17F production. Importantly, IL-36R signaling induced CCL7-mediated eosinophil recruitment to the inflamed skin. Last, S. aureus proteases induced IL-36α expression in keratinocytes, which promoted infiltration of IL-17-producing eosinophils. Collectively, we uncovered a mechanism for S. aureus proteases to trigger eosinophil-mediated skin inflammation, which has implications in the pathogenesis of inflammatory skin diseases.

Comparing different strategies to reduce hepatocellular damage in obese common marmosets (Callithrix jacchus).

BACKGROUND: Obesity in common marmosets (Callithrix jacchus) can lead to various liver pathologies. In other species, reduced caloric intake and weight loss improve prognosis, and, often, hepatoprotectants are used to halt or reverse hepatocellular damage from fat deposition in the liver. There are no published therapies for reducing hepatocellular damage in obese marmosets. METHODS: Fifteen obese marmosets were used to evaluate the ability of caloric restriction and pharmacologic therapy (S-adenosylmethionine + milk thistle extract, or SMT), alone and combined, to reduce elevated liver enzymes. Body weight and serum chemistries were measured every 4 weeks for 6 months. RESULTS: Across treatment groups, there was a significant reduction in liver enzymes ALT and AST over time. SMT alone significantly reduced liver enzymes ALT and AST at 6 months from baseline. CONCLUSIONS: Caloric restriction and SMT, alone and combined, are effective at reducing liver enzyme levels in obese marmosets.

Cardiac Rhabdomyoma in Four Göttingen Minipigs.

Göttingen minipigs are increasingly used as an alternative large animal model in nonclinical toxicology studies, and proliferative lesions in this species are rare. Here, we report four cases of cardiac rhabdomyoma in Göttingen minipigs, an incidental and benign mass in the heart. Three cases lacked gross observations and had a microscopic nodule in either the left ventricle or interventricular septum. The last case had a large, firm, raised nodule on a left ventricular papillary muscle noted at necropsy, with additional microscopic intramural masses in the left ventricular wall. In all cases, microscopic evaluation revealed well-circumscribed, expansile nodules composed of bundles of large, highly vacuolated, ovoid to polygonal cells with variable cytoplasmic processes radiating from a centrally located nucleus. Cells displayed patchy accumulation of intracytoplasmic, PAS-positive material and haphazardly arranged cytoplasmic cross-striations. There was no evidence of cardiac insufficiency or other data to suggest the masses were clinically meaningful. Cardiac rhabdomyomas have been reported in meat-hybrid swine, with a breed predisposition in red wattle. This lesion is well established in guinea pigs, but documentation in other laboratory species used in toxicologic studies is limited to two beagle dogs. To our knowledge, this is the first report of spontaneous cardiac rhabdomyoma in Göttingen minipigs.

Inhibition of host PARP1 contributes to the anti-inflammatory and antitubercular activity of pyrazinamide.

The antibiotic pyrazinamide (PZA) is a cornerstone of tuberculosis (TB) therapy that shortens treatment durations by several months despite being only weakly bactericidal. Intriguingly, PZA is also an anti-inflammatory molecule shown to specifically reduce inflammatory cytokine signaling and lesion activity in TB patients. However, the target and clinical importance of PZA's host-directed activity during TB therapy remain unclear. Here, we identify the host enzyme Poly(ADP-ribose) Polymerase 1 (PARP1), a pro-inflammatory master regulator strongly activated in TB, as a functionally relevant host target of PZA. We show that PZA inhibits PARP1 enzymatic activity in macrophages and in mice where it reverses TB-induced PARP1 activity in lungs to uninfected levels. Utilizing a PZA-resistant mutant, we demonstrate that PZA's immune-modulatory effects are PARP1-dependent but independent of its bactericidal activity. Importantly, PZA's bactericidal efficacy is impaired in PARP1-deficient mice, suggesting that immune modulation may be an integral component of PZA's antitubercular activity. In addition, adjunctive PARP1 inhibition dramatically reduces inflammation and lesion size in mice and may be a means to reduce lung damage and shorten TB treatment duration. Together, these findings provide insight into PZA's mechanism of action and the therapeutic potential of PARP1 inhibition in the treatment of TB.

Microphysiological Models of Lung Epithelium-Alveolar Macrophage Co-Cultures to Study Chronic Lung Disease.

The interactions between immune cells and epithelial cells influence the progression of many respiratory diseases, such as chronic obstructive pulmonary disease (COPD). In vitro models allow for the examination of cells in controlled environments. However, these models lack the complex 3D architecture and vast multicellular interactions between the lung resident cells and infiltrating immune cells that can mediate cellular response to insults. In this study, three complementary microphysiological systems are presented to delineate the effects of cigarette smoke and respiratory disease on the lung epithelium. First, the Transwell system allows the co-culture of pulmonary immune and epithelial cells to evaluate cellular and monolayer phenotypic changes in response to cigarette smoke exposure. Next, the human and mouse precision-cut lung slices system provides a physiologically relevant model to study the effects of chronic insults like cigarette smoke with the dissection of specific interaction of immune cell subtypes within the structurally complex tissue environment. Finally, the lung-on-a-chip model provides an adaptable system for live imaging of polarized epithelial tissues that mimic the in vivo environment of the airways. Using a combination of these models, a complementary approach is provided to better address the intricate mechanisms of lung disease.