CCR2/CCR5-mediated macrophage-smooth muscle cell crosstalk in pulmonary hypertension.

Macrophages are major players in the pathogenesis of pulmonary arterial hypertension (PAH).To investigate whether lung macrophages and pulmonary-artery smooth muscle cells (PASMCs) collaborate to stimulate PASMC growth and whether the CCL2-CCR2 and CCL5-CCR5 pathways inhibited macrophage-PASMC interactions and PAH development, we used human CCR5-knock-in mice and PASMCs from patients with PAH and controls.Conditioned media from murine M1 or M2 macrophages stimulated PASMC growth. This effect was markedly amplified with conditioned media from M2 macrophage/PASMC co-cultures. CCR2, CCR5, CCL2 and CCL5 were upregulated in macrophage/PASMC co-cultures. Compared to inhibiting either receptor, dual CCR2 and CCR5 inhibition more strongly attenuated the growth-promoting effect of conditioned media from M2-macrophage/PASMC co-cultures. Deleting either CCR2 or CCR5 in macrophages or PASMCs attenuated the growth response. In mice with hypoxia- or SUGEN/hypoxia-induced PH, targeting both CCR2 and CCR5 prevented or reversed PH more efficiently than targeting either receptor alone. Patients with PAH exhibited CCR2 and CCR5 upregulation in PASMCs and perivascular macrophages compared to controls. The PASMC growth-promoting effect of conditioned media from M2-macrophage/PASMC co-cultures was greater when PASMCs from PAH patients were used in the co-cultures or as the target cells and was dependent on CCR2 and CCR5. PASMC migration toward M2-macrophages was greater with PASMCs from PAH patients and was attenuated by blocking CCR2 and CCR5.CCR2 and CCR5 are required for collaboration between macrophages and PASMCs to initiate and amplify PASMC migration and proliferation during PAH development. Dual targeting of CCR2 and CCR5 may hold promise for treating human PAH.

New Nitric Oxide Donor NCX 1443: Therapeutic Effects on Pulmonary Hypertension in the SAD Mouse Model of Sickle Cell Disease.

Nitric oxide (NO) donors may be useful for treating pulmonary hypertension (PH) complicating sickle cell disease (SCD), as endogenous NO is inactivated by hemoglobin released by intravascular hemolysis. Here, we investigated the effects of the new NO donor NCX1443 on PH in transgenic SAD mice, which exhibit mild SCD without severe hemolytic anemia. In SAD and wild-type (WT) mice, the pulmonary pressure response to acute hypoxia was similar and was abolished by 100 mg/kg NCX1443. The level of PH was also similar in SAD and WT mice exposed to chronic hypoxia (9% O2) alone or with SU5416 and was similarly reduced by daily NCX1443 gavage. Compared with WT mice, SAD mice exhibited higher levels of HO-1, endothelial NO synthase, and PDE5 but similar levels of lung cyclic guanosine monophosphate. Cultured pulmonary artery smooth muscle cells from SAD mice grew faster than those from WT mice and had higher PDE5 protein levels. Combining NCX1443 and a PDE5 inhibitor suppressed the growth rate difference between SAD and WT cells and induced a larger reduction in hypoxic PH severity in SAD than in WT mice. By amplifying endogenous protective mechanisms, NCX1443 in combination with PDE5 inhibition may prove useful for treating PH complicating SCD.

Roles for the CX3CL1/CX3CR1 and CCL2/CCR2 Chemokine Systems in Hypoxic Pulmonary Hypertension.

Monocytes/macrophages are major effectors of lung inflammation associated with various forms of pulmonary hypertension (PH). Interactions between the CCL2/CCR2 and CX3CL1/CX3CR1 chemokine systems that guide phagocyte infiltration are incompletely understood. Our objective was to explore the individual and combined actions of CCL2/CCR2 and CX3CL1/CX3CR1 in hypoxia-induced PH in mice; particularly their roles in monocyte trafficking, macrophage polarization, and pulmonary vascular remodeling. The development of hypoxia-induced PH was associated with marked increases in lung levels of CX3CR1, CCR2, and their respective ligands, CX3CL1 and CCL2. Flow cytometry revealed that both inflammatory Ly6Chi and resident Ly6Clo monocyte subsets exhibited sustained increases in blood and a transient peak in lung tissue, and that lung perivascular and alveolar macrophage counts showed sustained elevations. CX3CR1-/- mice were protected against hypoxic PH compared with wild-type mice, whereas CCL2-/- mice and double CX3CR1-/-/CCL2-/- mice exhibited similar PH severity, as did wild-type mice. The protective effects of CX3CR1 deficiency occurred concomitantly with increases in lung monocyte and macrophage counts and with a change from M2 to M1 macrophage polarization that markedly diminished the ability of conditioned media to induce pulmonary artery smooth muscle cell (PA-SMC) proliferation, which was partly dependent on CX3CL1 secretion. Results in mice given the CX3CR1 inhibitor F1 were similar to those in CX3CR1-/- mice. In conclusion, CX3CR1 deficiency protects against hypoxia-induced PH by modulating monocyte recruitment, macrophage polarization, and PA-SMC cell proliferation. Targeting CX3CR1 may hold promise for treating PH.

Osteopontin, a Key Mediator Expressed by Senescent Pulmonary Vascular Cells in Pulmonary Hypertension.

OBJECTIVE: Senescent pulmonary artery smooth muscle cells (PA-SMCs) may contribute to the pathogenesis of pulmonary hypertension by producing secreted factors. The aim of this study was to explore the role in pulmonary hypertension of extracellular matrix proteins released by senescent PA-SMCs. APPROACH AND RESULTS: Polymerase chain reaction array analysis of human PA-SMCs undergoing replicative senescence revealed osteopontin upregulation, which mediated the stimulatory effect of senescent PA-SMC media and matrix on PA-SMC growth and migration. Osteopontin was upregulated in lungs from patients with chronic obstructive pulmonary disease or idiopathic pulmonary arterial hypertension. Prominent osteopontin immunostaining was noted in PA-SMCs that also stained for p16 at sites of vascular hypertrophy, and lung osteopontin levels correlated closely with age. Compared with younger mice, 1-year-old mice displayed higher lung osteopontin levels, right ventricular systolic pressure, pulmonary vessel muscularization, and numbers of PA-SMCs stained for p16 or p21 and also for osteopontin. No such changes with age were observed in osteopontin(-/-) mice, which developed attenuated pulmonary hypertension during hypoxia. Compared with cultured PA-SMCs from young mice, PA-SMCs from 1-year-old mice grew faster; a similar fast growth rate was seen with PA-SMCs from young mice stimulated by matrix or media from old mice. Differences between old/young mouse PA-SMC growth rates were suppressed by antiosteopontin antibodies. PA-SMCs from osteopontin(-/-) mice grew more slowly than did wild-type PA-SMCs; they were stimulated by wild-type PA-SMCs media and matrix, and this effect was stronger with PA-SMCs from older versus younger mice. CONCLUSIONS: Osteopontin is a key mediator released by senescent PA-SMCs and contributing to pulmonary hypertension progression.

Extracellular Calpain/Calpastatin Balance Is Involved in the Progression of Pulmonary Hypertension.

Excessive growth of pulmonary arterial (PA) smooth muscle cells (SMCs) is a major component of PA hypertension (PAH). The calcium-activated neutral cysteine proteases calpains 1 and 2, expressed by PASMCs, contribute to PH but are tightly controlled by a single specific inhibitor, calpastatin. Our objective was to investigate calpastatin during pulmonary hypertension (PH) progression and its potential role as an intracellular and/or extracellular effector. We assessed calpains and calpastatin in patients with idiopathic PAH and mice with hypoxic or spontaneous (SM22-5HTT(+) strain) PH. To assess intracellular and extracellular roles for calpastatin, we studied effects of the calpain inhibitor PD150606 on hypoxic PH in mice with calpastatin overexpression driven by the cytomegalovirus promoter (CMV-Cast) or C-reactive protein (CRP) promoter (CRP-Cast), inducing increased calpastatin production ubiquitously and in the liver, respectively. Chronically hypoxic and SM22-5HTT(+) mice exhibited increased lung calpastatin and calpain 1 and 2 protein levels and activity, both intracellularly and extracellularly. Prominent calpastatin and calpain immunostaining was found in PASMCs of remodeled vessels in mice and patients with PAH, who also exhibited increased plasma calpastatin levels. CMV-Cast and CRP-Cast mice showed similarly decreased PH severity compared with wild-type mice, with no additional effect of PD150606 treatment. In cultured PASMCs from wild-type and CMV-Cast mice, exogenous calpastatin decreased cell proliferation and migration with similar potency as PD150606 and suppressed fibronectin-induced potentiation. These results indicate that calpastatin limits PH severity via extracellular mechanisms. They suggest a new approach to the development of treatments for PH.

Selective Tuberous Sclerosis Complex 1 Gene Deletion in Smooth Muscle Activates Mammalian Target of Rapamycin Signaling and Induces Pulmonary Hypertension.

Constitutive activation of the mammalian target of rapamycin (mTOR) complexes mTORC1 and mTORC2 is associated with pulmonary hypertension (PH) and sustained growth of pulmonary artery (PA) smooth muscle cells (SMCs). We investigated whether selective mTORC1 activation in SMCs induced by deleting the negative mTORC1 regulator tuberous sclerosis complex 1 gene (TSC1) was sufficient to produce PH in mice. Mice expressing Cre recombinase under SM22 promoter control were crossed with TSC1(LoxP/LoxP) mice to generate SM22-TSC1(-/-) mice. At 8 weeks of age, SM22-TSC1(-/-) mice exhibited PH with marked increases in distal PA muscularization and Ki67-positive PASMC counts, without systemic hypertension or cardiac dysfunction. Marked activation of the mTORC1 substrates S6 kinase and 4E-BP and the mTORC2 substrates p-Akt(Ser473) and glycogen synthase kinase 3 was found in the lungs and pulmonary vessels of SM22-TSC1(-/-) mice when compared with control mice. Treatment with 5 mg/kg rapamycin for 3 weeks to inhibit mTORC1 and mTORC2 fully reversed PH in SM22-TSC1(-/-) mice. In chronically hypoxic mice and SM22-5HTT(+) mice exhibiting PH associated with mTORC1 and mTORC2 activation, PH was maximally attenuated by low-dose rapamycin associated with selective mTORC1 inhibition. Cultured PASMCs from SM22-TSC1(-/-), SM22-5HTT(+), and chronically hypoxic mice exhibited similar sustained growth-rate enhancement and constitutive mTORC1 and mTORC2 activation; both effects were abolished by rapamycin. Deletion of the downstream mTORC1 effectors S6 kinase 1/2 in mice also activated mTOR signaling and induced PH. We concluded that activation of mTORC1 signaling leads to increased PASMC proliferation and subsequent PH development.

Role for telomerase in pulmonary hypertension.

BACKGROUND: Cells exhibiting dysregulated growth may express telomerase reverse transcriptase (TERT), the dual function of which consists of maintaining telomere length, in association with the RNA template molecule TERC, and controlling cell growth. Here, we investigated lung TERT in human and experimental pulmonary hypertension (PH) and its role in controlling pulmonary artery smooth muscle cell (PA-SMC) proliferation. METHODS AND RESULTS: Marked TERT expression or activity was found in lungs from patients with idiopathic PH and from mice with PH induced by hypoxia or serotonin-transporter overexpression (SM22-5HTT(+) mice), chiefly within PA-SMCs. In cultured mouse PA-SMCs, TERT was expressed on growth stimulation by serum. The TERT inhibitor imetelstat and the TERT activator TA65 abrogated and stimulated PA-SMC growth, respectively. PA-SMCs from PH mice showed a heightened proliferative phenotype associated with increased TERT expression, which was suppressed by imetelstat treatment. TERC(-/-) mice at generation 2 and TERT(-/-) mice at generations 2, 3, and 4 developed less severe PH than did wild-type mice exposed to chronic hypoxia, with less distal pulmonary artery muscularization and fewer Ki67-stained proliferating PA-SMCs. Telomere length differed between TERC(-/-) and TERT(-/-) mice, whereas PH severity was similar in the 2 strains and across generations. Chronic imetelstat treatment reduced hypoxia-induced PH in wild-type mice or partially reversed established PH in SM22-5HTT(+) mice while simultaneously decreasing TERT expression. Opposite effects occurred in mice treated with TA65. CONCLUSIONS: Telomerase exerts telomere-independent effects on PA-SMC growth in PH and may constitute a treatment target for PH.

Role of interleukin-1 receptor 1/MyD88 signalling in the development and progression of pulmonary hypertension.

Pulmonary artery smooth muscle cell (PA-SMC) proliferation and inflammation are key components of pulmonary arterial hypertension (PAH). Interleukin (IL)-1ß binds to IL-1 receptor (R)1, thereby recruiting the molecular adaptor myeloid differentiation primary response protein 88 (MyD88) (involved in IL-1R1 and Toll-like receptor signal transduction) and inducing IL-1, IL-6 and tumour necrosis factor-α synthesis through nuclear factor-κB activation.We investigated the IL-1R1/MyD88 pathway in the pathogenesis of pulmonary hypertension.Marked IL-1R1 and MyD88 expression with predominant PA-SMC immunostaining was found in lungs from patients with idiopathic PAH, mice with hypoxia-induced pulmonary hypertension and SM22-5-HTT(+) mice. Elevations in lung IL-1ß, IL-1R1, MyD88 and IL-6 preceded pulmonary hypertension in hypoxic mice. IL-1R1(-/-), MyD88(-/-) and control mice given the IL-1R1 antagonist anakinra were protected similarly against hypoxic pulmonary hypertension and perivascular macrophage recruitment. Anakinra reversed pulmonary hypertension partially in SM22-5-HTT(+) mice and markedly in monocrotaline-treated rats. IL-1ß-mediated stimulation of mouse PA-SMC growth was abolished by anakinra and absent in IL-1R1(-/-) and MyD88(-/-) mice. Gene deletion confined to the myeloid lineage (M.lys-Cre MyD88(fl/fl) mice) decreased pulmonary hypertension severity versus controls, suggesting IL-1ß-mediated effects on PA-SMCs and macrophages. The growth-promoting effect of media conditioned by M1 or M2 macrophages from M.lys-Cre MyD88(fl/fl) mice was attenuated.Pulmonary vessel remodelling and inflammation during pulmonary hypertension require IL-1R1/MyD88 signalling. Targeting the IL-1ß/IL-1R1 pathway may hold promise for treating human PAH.

CCR5 as a treatment target in pulmonary arterial hypertension.

BACKGROUND: Pulmonary arterial hypertension (PH), whether idiopathic or related to underlying diseases such as HIV infection, results from complex vessel remodeling involving both pulmonary artery smooth muscle cell (PA-SMC) proliferation and inflammation. CCR5, a coreceptor for cellular HIV-1 entry expressed on macrophages and vascular cells, may be involved in the pathogenesis of PH. Maraviroc is a new CCR5 antagonist designed to block HIV entry. METHODS AND RESULTS: Marked CCR5 expression was found in lungs from patients with idiopathic PH, in mice with hypoxia-induced PH, and in Simian immunodeficiency virus-infected macaques, in which it was localized chiefly in the PA-SMCs. To assess the role for CCR5 in experimental PH, we used both gene disruption and pharmacological CCR5 inactivation in mice. Because maraviroc does not bind to murine CCR5, we used human-CCR5ki mice for pharmacological and immunohistochemical studies. Compared with wild-type mice, CCR5-/- mice or human-CCR5ki mice treated with maraviroc exhibited decreased PA-SMC proliferation and recruitment of perivascular and alveolar macrophages during hypoxia exposure. CCR5-/- mice reconstituted with wild-type bone marrow cells and wild-type mice reconstituted with CCR5-/- bone marrow cells were protected against PH, suggesting CCR5-mediated effects on PA-SMCs and macrophage involvement. The CCR5 ligands CCL5 and the HIV-1 gp120 protein increased intracellular calcium and induced growth of human and human-CCR5ki mouse PA-SMCs; maraviroc inhibited both effects. Maraviroc also reduced the growth-promoting effects of conditioned media from CCL5-activated macrophages derived from human-CCR5ki mice on PA-SMCs from wild-type mice. CONCLUSION: The CCL5-CCR5 pathway represents a new therapeutic target in PH associated with HIV or with other conditions.

Genomic Instability and Protumoral Inflammation Are Associated with Primary Resistance to Anti-PD-1 + Antiangiogenesis in Malignant Pleural Mesothelioma.

Cancer immunotherapy combinations have recently been shown to improve the overall survival of advanced mesotheliomas, especially for patients responding to those treatments. We aimed to characterize the biological correlates of malignant pleural mesotheliomas' primary resistance to immunotherapy and antiangiogenics by testing the combination of pembrolizumab, an anti-PD-1 antibody, and nintedanib, a pan-antiangiogenic tyrosine kinase inhibitor, in the multicenter PEMBIB trial (NCT02856425). Thirty patients with advanced malignant pleural mesothelioma were treated and explored. Unexpectedly, we found that refractory patients were actively recruiting CD3+CD8+ cytotoxic T cells in their tumors through CXCL9 tumor release upon treatment. However, these patients displayed high levels of somatic copy-number alterations in their tumors that correlated with high blood and tumor levels of IL6 and CXCL8. Those proinflammatory cytokines resulted in higher tumor secretion of VEGF and tumor enrichment in regulatory T cells. Advanced mesothelioma should further benefit from stratified combination therapies adapted to their tumor biology. SIGNIFICANCE: Sequential explorations of fresh tumor biopsies demonstrated that mesothelioma resistance to anti-PD-1 + antiangiogenics is not due to a lack of tumor T-cell infiltration but rather due to adaptive immunosuppressive pathways by tumors, involving molecules (e.g., IL6, CXCL8, VEGF, and CTLA4) that are amenable to targeted therapies. This article is highlighted in the In This Issue feature, p. 799.

Safety, recommended dose, efficacy and immune correlates for nintedanib in combination with pembrolizumab in patients with advanced cancers.

BACKGROUND: We aimed to determine the safety and efficacy of nintedanib, an oral anti-angiogenic tyrosine kinase inhibitor, in combination with pembrolizumab, an anti-PD1 immunotherapy, in patients with advanced solid tumors (PEMBIB trial; NCT02856425). METHODS: In this monocentric phase Ib dose escalation cohort, we evaluated escalating doses of nintedanib (Dose level 1 (DL1) = 150 mg bid [bis in die, as twice a day]; DL2 = 200 mg bid, oral delivery) in combination with pembrolizumab (200 mg Q3W, IV). Patients received a 1-week lead-in dose of nintedanib monotherapy prior starting pembrolizumab. The primary objective was to establish the maximum tolerated dose (MTD) of the combination based on dose limiting toxicity (DLT) occurrence during the first 4 weeks. Secondary objectives were to assess the anti-tumor efficacy and to identify the associated immune and angiogenic parameters in order to establish the recommended nintedanib dose for expansion cohorts. Flow cytometry (FC), Immuno-Histo-Chemistry (IHC) and electrochemiluminescence multi-arrays were prospectively performed on baseline & on-treatment tumor and blood samples to identify immune correlates of efficacy. RESULTS: A total of 12/13 patients enrolled were evaluable for DLT (1 patient withdrew consent prior receiving pembrolizumab). Three patients at 200 mg bid experienced a DLT (grade 3 liver enzymes increase). Four patients developed grade 1-2 immune related adverse events (irAE). Eight patients died because of cancer progression. Median follow-up was 23.7 months (95%CI: 5.55-40.5). Three patients developed a partial response (PR) (ORR = 25%) and five patients (42%) had durable clinical benefit (DCB), defined as PR or stable disease (SD) ≥ 6 months. At baseline, patients with DCB had higher plasma levels of Tie2, CXCL10, CCL22 and circulating CD4+ PD1+ OX40+ T cells than patients without DCB. Patients with DCB presented also with more DC-LAMP+ dendritic cells, CD3+ T cells and FOXP3+ Tregs in baseline tumor biopsies. For DCB patients, the nintedanib lead-in monotherapy resulted in higher blood CCL3, Tregs and CCR4+ CXCR3+ CXCR5- memory CD4 T cells. After the first pembrolizumab infusion, patients with DCB showed lower IL-6, IL-8, IL-27 plasma levels. CONCLUSION: Nintedanib 150 mg bid is the recommended dose for combination with pembrolizumab and is currently investigated in multiple expansion cohorts. Early tumoral and circulating immune factors were associated with cancer outcome under nintedanib & pembrolizumab therapy. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02856425 . Registered August 4, 2016 - Prospectively registered.

mTOR pathway activation drives lung cell senescence and emphysema.

Chronic obstructive pulmonary disease (COPD) is a highly prevalent and devastating condition for which no curative treatment is available. Exaggerated lung cell senescence may be a major pathogenic factor. Here, we investigated the potential role for mTOR signaling in lung cell senescence and alterations in COPD using lung tissue and derived cultured cells from patients with COPD and from age- and sex-matched control smokers. Cell senescence in COPD was linked to mTOR activation, and mTOR inhibition by low-dose rapamycin prevented cell senescence and inhibited the proinflammatory senescence-associated secretory phenotype. To explore whether mTOR activation was a causal pathogenic factor, we developed transgenic mice exhibiting mTOR overactivity in lung vascular cells or alveolar epithelial cells. In this model, mTOR activation was sufficient to induce lung cell senescence and to mimic COPD lung alterations, with the rapid development of lung emphysema, pulmonary hypertension, and inflammation. These findings support a causal relationship between mTOR activation, lung cell senescence, and lung alterations in COPD, thereby identifying the mTOR pathway as a potentially new therapeutic target in COPD.