p53 in Bronchial Club Cells Facilitates Chronic Lung Inflammation by Promoting Senescence

The tumor suppressor p53 limits tumorigenesis by inducing apoptosis, cell cycle arrest, and senescence. Although p53 is known to limit inflammation during tumor development, its role in regulating chronic lung inflammation is less well understood. To elucidate the function of airway epithelial p53 in such inflammation, we subjected genetically modified mice, whose bronchial epithelial club cells lack p53, to repetitive inhalations of lipopolysaccharide (LPS), an exposure that leads to severe chronic bronchitis and airway senescence in wild-type mice. Surprisingly, the club cell p53 knockout mice exhibited reduced airway senescence and bronchitis in response to chronic LPS exposure and were significantly protected from global lung destruction. Furthermore, pharmacological elimination of senescent cells also protected wild-type mice from chronic LPS-induced bronchitis. Our results implicate p53 in induction of club-cell senescence and correlate epithelial cell senescence of chronic airway inflammation and lung destruction.

High avidity TCR-peptide interactions between CD4 lymphocytes and lymph node dendritic cells promote normal lymphocyte arrest, activation, proliferation, and differentiation independently of dendritic cell ICAM-1 and 2

The two main LFA-1 ligands ICAM-1 and ICAM-2 are constitutively co-expressed on antigen presenting cells (APCs) and on the lymph node stroma. We find abrogated antigen specific CD4 T cell priming in ICAM-1 and ICAM-2 deficient spleens. Nevertheless, the in vivo contribution of these ligands to lymphocyte activation proliferation and differentiation in lymph nodes has been difficult to dissect in total knockout mice due to their multiple roles in lymphocyte entry and priming in these organs. We therefore constructed lethally irradiated chimeric mice reconstituted with ICAM-1 and 2 double knock out (DKO) APCs in which lymphocyte entry into peripheral lymph nodes was reconstituted. Strikingly, these mice elicited normal antigen specific OT-II T cell activation, proliferation and differentiation into Th1 and Tfh effectors. OT-II T cells could also normally arrest on DCs deficient in ICAM-1 and 2. A compensatory role of VCAM-1 in ICAM deficient DCs was ruled out. Nevertheless, polyclonal T cell proliferation in response to endogenous self-antigens required the presence of ICAM-1 and ICAM-2 on endogenous lymph node DCs. Our results are the first indication that high avidity TCR peptide-MHC-II recognition can bypass integrin-mediated lymphocyte adhesions to DCs under specific settings.

Lung ICAM-1 and ICAM-2 support spontaneous intravascular effector lymphocyte entrapment but are not required for neutrophil entrapment or emigration inside endotoxin-inflamed lungs

The pulmonary vasculature constitutively expresses the integrin lymphocyte function-associated antigen-1 ligands intercellular adhesion molecule (ICAM)-1 and -2. In this study, effector T cells were temporarily entrapped by the lung vasculature on their way to inflamed lymph nodes, and this entrapment was strongly reduced in ICAM-1 and -2 double-deficient mice (79 and 86% reduction for CD8(+) and CD4(+) effectors, respectively, compared with wild-type mice). Although the pulmonary vasculature has been suggested to be masked by the heparan sulfate-containing glycocalyx, which is susceptible to heparanase-mediated shedding, lung and lymphocyte heparanase have been found to be unnecessary for this entrapment. Systemic LPS induced rapid neutrophil entrapment in the lung vasculature, but in contrast to T-cell entrapment, this sequestration was ICAM-1, ICAM-2, and heparanase independent. Furthermore, neutrophil migration into the bronchoalveolar space induced by LPS inhalation and LPS-induced leakage of red blood cells into this space were not dependent on lung ICAMs or heparanase activity. Nevertheless, heparanase was critical for neutrophil accumulation in smoke-exposed lungs. Our results indicate that, whereas T cells use ICAM-1 and -2 for temporary pulmonary entrapment, neutrophils get sequestered and extravasate into inflamed lungs independent of ICAMs. This is the first demonstration that the pulmonary vasculature is differentially recognized by T cells and neutrophils.-Petrovich, E., Feigelson, S. W., Stoler-Barak, L., Hatzav, M., Solomon, A., Bar-Shai, A., Ilan, N., Li, J.-P., Engelhardt, B., Vlodavsky, I., Alon, R. Lung ICAM-1 and ICAM-2 support spontaneous intravascular effector lymphocyte entrapment but are not required for neutrophil entrapment or emigration inside endotoxin-inflamed lungs.

Interaction with therapeutic soft contact lenses affects the intraocular efficacy of tropicamide and latanoprost in dogs

Therapeutic soft contact lenses (TSCLs) are frequently used to support or protect the cornea during healing. Our aim was to quantitatively evaluate the efficacy of topical medications in TSCL-fitted dogs and determine whether it is affected by the presence of TSCLs. In Phase I, pupil diameter was measured in eyes treated with tropicamide and in eyes covered with TSCLs and then treated with tropicamide, with 1-week intervals between sessions. In Phase II, intraocular pressure (IOP) was measured in uncovered and TSCL-covered eyes treated with latanoprost, with 1-week intervals between sessions. Tropicamide caused significant mydriasis in both uncovered and TSCL-covered eyes (P = 0.005). On the other hand, latanoprost caused a significant decrease in IOP when applied to uncovered eyes (P = 0.002), but had no significant effect on IOP when applied to TSCL-covered eyes (P = 0.7). As we used the same dogs and identical TSCLs throughout the study, we conclude that the different outcomes of the two drugs are due to properties of the drugs themselves, or their formulations, affecting their interaction with the TSCLs. The clinical efficacy of topical drugs applied to TSCL-covered eyes may have to be determined for each drug and/or formulation.

Heparanase of murine effector lymphocytes and neutrophils is not required for their diapedesis into sites of inflammation

Heparanase, the exclusive mammalian heparan sulfate-degrading enzyme, has been suggested to be utilized by leukocytes to penetrate through the dense basement membranes surrounding blood venules. Despite its established role in tumor cell invasion, heparanase function in leukocyte extravasation has never been demonstrated. We found that TH1/TC1-type effector T cells are highly enriched for this enzyme, with a 3.6-fold higher heparanase mRNA expression compared with naive lymphocytes. Using adoptive transfer of wild-type and heparanase-deficient effector T cells into inflamed mice, we show that T-cell heparanase was not required for extravasation inside inflamed lymph nodes or skin. Leukocyte extravasation through acute inflamed skin vessels was also heparanase independent. Furthermore, neutrophils emigrated to the inflamed peritoneal cavity independently of heparanase expression on either the leukocytes or on the endothelial and mesothelial barriers, and overexpression of the enzyme on neutrophils did not facilitate their emigration. However, heparanase absence significantly reduced monocyte emigration into the inflamed peritoneal cavity. These results collectively suggest that neither leukocyte nor endothelial heparanase is required for T-cell and neutrophil extravasation through inflamed vascular barriers, whereas this enzyme is required for optimal monocyte recruitment to inflamed peritoneum.

Blood vessels pattern heparan sulfate gradients between their apical and basolateral aspects

A hallmark of immune cell trafficking is directional guidance via gradients of soluble or surface bound chemokines. Vascular endothelial cells produce, transport and deposit either their own chemokines or chemokines produced by the underlying stroma. Endothelial heparan sulfate (HS) was suggested to be a critical scaffold for these chemokine pools, but it is unclear how steep chemokine gradients are sustained between the lumenal and ablumenal aspects of blood vessels. Addressing this question by semi-quantitative immunostaining of HS moieties around blood vessels with a pan anti-HS IgM mAb, we found a striking HS enrichment in the basal lamina of resting and inflamed post capillary skin venules, as well as in high endothelial venules (HEVs) of lymph nodes. Staining of skin vessels with a glycocalyx probe further suggested that their lumenal glycocalyx contains much lower HS density than their basolateral extracellular matrix (ECM). This polarized HS pattern was observed also in isolated resting and inflamed microvascular dermal cells. Notably, progressive skin inflammation resulted in massive ECM deposition and in further HS enrichment around skin post capillary venules and their associated pericytes. Inflammation-dependent HS enrichment was not compromised in mice deficient in the main HS degrading enzyme, heparanase. Our results suggest that the blood vasculature patterns steep gradients of HS scaffolds between their lumenal and basolateral endothelial aspects, and that inflammatory processes can further enrich the HS content nearby inflamed vessels. We propose that chemokine gradients between the lumenal and ablumenal sides of vessels could be favored by these sharp HS scaffold gradients.