Mice sensitized to ovalbumin (OVA) develop a biphasic response to OVA aerosols, such that acute exposure results in allergic airway disease (AAD) while chronic exposure results in local inhalational tolerance (LIT), with resolution of local pulmonary responses but persistence of the systemic allergic response. We have previously reported that B cell lymphocytosis persists in hilar lymph nodes (HLN) during LIT and that CD4+CD25+Foxp3+ Treg cells are significantly increased in the HLN of LIT mice. This raised the consideration that B cells were involved in modulating the LIT response. Methods and Results: CD19+ B cells isolated from HLN of LIT mice were transferred to sensitized mice before inhaled antigen challenge. Compared to vehicle or AAD CD19+ transferred mice, LIT CD19+ transferred mice developed less BAL leukocytosis and eosinophilia (p < 0.05). In vivo, mice with attenuated AAD following LIT HLN B cell transfer showed a significant increase in the percentages of CD4+ Foxp3+ Treg cells in BAL and HLN, but not systemically (p < 0.03). This protection was antigen specific as LIT HLN B cells did not limit inflammation when transferred to bovine serum albumin (BSA) sensitized mice that were subsequently aerosolized with BSA. In vitro, LIT HLN B cells induced conversion of CD4+CD25‐ Teff cells to CD4+CD25+Foxp3+ T regulatory cells (Treg). The ability to induce suppressive Treg cells was regional, since B cells from AAD or systemic sites during LIT failed to do so. CFSE labeling of LIT HLN B cells demonstrated that these B cells home in and are retained at active sites of inflammation. Conclusions: These observations support a novel mechanism of regional immune regulation, possibly related to the development of a subset of regulatory B cells within the LIT HLN B cell population. This work was funded by NIH/AI R01 HL‐43573

In a biphasic, ovalbumin (OVA)-induced murine asthma model where allergic airway disease is followed by resolution and the development of local inhalational tolerance (LIT), TGFβ-expressing CD5+ B cells were selectively expanded locally in hilar lymph nodes (HLN) of LIT mice. LIT HLN CD5+ B cells but not LIT HLN CD5− B cells induced expression of Foxp3 in CD4+ CD25− T cells in vitro. These CD5+ regulatory B cells and CD4+Foxp3+ T cells demonstrated similar increases in expression of chemokine receptors (CXCR4 and CXCR5) and co-localized in HLN B cell zones of LIT mice. The adoptive transfer of LIT HLN CD5+ B cells, but not LIT HLN CD5− B cells, increased the number of CD4+Foxp3+ T cells in the lung and inhibited airway eosinophilia in this OVA model. Thus, regulatory B cells in HLNs of LIT mice reside in a CD5+ TGFβ-producing subpopulation and co-localize with CD4+Foxp3+ T cells.

Bromelain attenuated development of AAD while altering CD4+ to CD8+ T lymphocyte populations. The reduction in AAD outcomes suggests that bromelain may have similar effects in the treatment of human asthma and hypersensitivity disorders.

Thrall RS, Maulik N. Bromelain induces cardioprotection against ischemia-reperfusion injury through Akt/FOXO pathway in rat myocardium. Am J Physiol Heart Circ Physiol 294: H1365-H1370, 2008. First published January 11, 2008 doi:10.1152/ajpheart.01005.2007, a proteolytic enzyme extracted from the stem of the pineapple, is known to possess anti-inflammatory activity and has been shown to reduce blood viscosity, prevent the aggregation of blood platelets, and improve ischemia-reperfusion (I/R) injury in a skeletal muscle model. We investigated the capacity of Br to limit myocardial injury in a global I/R model. Adult male Sprague-Dawley rats were divided into two groups: control (PBS) and Br at 10 mg/kg in PBS administered via intraperitoneal injection (twice/day) for 15 consecutive days. On day 16, the hearts were excised and subjected to 30 min of global ischemia followed by 2 h of reperfusion. Br treatment showed higher left ventricular functional recovery throughout reperfusion compared with the controls [maximum rate of rise in intraventricular pressure (dP/dt max), 2,225 vs. 1,578 mmHg/s at 2 h reperfusion]. Aortic flow was also found to be increased in Br treatment when compared with that in untreated rats (11 vs. 1 ml). Furthermore, Br treatment reduced both the infarct size (34% vs. 43%) and the degree of apoptosis (28% vs. 37%) compared with the control animals. Western blot analysis showed an increased phosphorylation of both Akt and FOXO3A in the treatment group compared with the control. These results demonstrated for the first time that Br triggers an Akt-dependent survival pathway in the heart, revealing a novel mechanism of cardioprotective action and a potential therapeutic target against I/R injury. apoptosis; myocardial infarction; Ananas comosus; forkhead transcription factor MYOCARDIAL ISCHEMIA-REPERFUSION (I/R) injury occurs in a wide spectrum of disorders ranging from cardiac arrest to acute myocardial infarction and represents a major public health concern. Ischemia induces several pathological changes due to lack of oxygen supply to the myocardium (16), and postischemic reperfusion worsens the injury. Modulation of the adaptive response to ischemic heart disease has become a major research interest. Pharmacological preconditioning plays a prominent role in reducing such tissue damage in response to I/R injury. In this respect, bromelain (Br), which is a descriptor for a family of sulfhydryl proteolytic enzymes extracted from the stem of Ananas comosus, the common pineapple plant (13, 23), has shown promise. Br is composed of several distinct cysteine proteolytic fractions ranging in size from 15 to 27 kDa and is commonly delivered as a powder in a gelatin or enteric-coated capsule. Reports suggest that oral administration of Br inhibits time-dependent thrombus formation in a laser thrombosis model and reduces human platelet aggregation both in vitro and in vivo (10). Br, when combined with rutin and trypsin, was also shown to have a protective effect on the skeletal muscle during I/R inju...

Bromelain, a widely used pineapple extract with cysteine protease activity, has been shown to have immunomodulatory effects in a variety of immune system models. The purpose of the present study was to determine the effects of orally administered bromelain in an ovalbumin (OVA)-induced murine model of acute allergic airway disease (AAD). To establish AAD, female C57BL/6J mice were sensitized with intraperitoneal (i.p.) OVA/alum and then challenged with OVA aerosols for 3 days. Mice were gavaged with either (phosphate buffered saline)PBS or 200 mg/kg bromelain in PBS, twice daily for four consecutive days, beginning 1 day prior to OVA aerosol challenge. Airway reactivity and methacholine sensitivity, bronchoalveolar lavage (BAL) cellular differential, Th2 cytokines IL-5 and IL-13, and lung histology were compared between treatment groups. Oral bromelain-treatment of AAD mice demonstrated therapeutic efficacy as evidenced by decreased methacholine sensitivity (P ≤ 0.01), reduction in BAL eosinophils (P ≤ 0.02) and IL-13 concentrations (P ≤ 0.04) as compared with PBS controls. In addition, oral bromelain significantly reduced BAL CD19+ B cells (P ≤ 0.0001) and CD8+ T cells (P ≤ 0.0001) in AAD mice when compared with controls. These results suggest that oral treatment with bromelain had a beneficial therapeutic effect in this murine model of asthma and bromelain may also be effective in human conditions.