Scientific and Artful Voices of Resilience.

Resilience is a fluid trait that is triggered by personal experience. It is, arguably, a necessity for a scientist. What is it? You know it, when you see it. One thing is for certain: resilience reflects the dynamic toggle between change and an individual's identity.

The Pioglitazone Trek via Human PPAR Gamma: From Discovery to a Medicine at the FDA and Beyond.

For almost two decades, pioglitazone has been prescribed primarily to prevent and treat insulin resistance in some type 2 diabetic patients. In this review, we trace the path to discovery of pioglitazone as a thiazolidinedione compound, the glitazone tracks through the regulatory agencies, the trek to molecular agonism in the nucleus and the binding of pioglitazone to the nuclear receptor PPAR gamma. Given the rise in consumption of pioglitazone in T2D patients worldwide and the increased number of clinical trials currently testing alternate medical uses for this drug, there is also merit to some reflection on the reported adverse effects. Going forward, it is imperative to continue investigations into the mechanisms of actions of pioglitazone, the potential of glitazone drugs to contribute to unmet needs in complex diseases associated with the dynamics of adaptive homeostasis, and also the routes to minimizing adverse effects in every-day patients throughout the world.

The peroxisome proliferator-activated receptor-gamma agonist pioglitazone represses inflammation in a peroxisome proliferator-activated receptor-alpha-dependent manner in vitro and in vivo in mice.

OBJECTIVES: Our aim was to investigate if the peroxisome proliferator-activated receptor (PPAR)-gamma agonist pioglitazone modulates inflammation through PPARalpha mechanisms. BACKGROUND: The thiazolidinediones (TZDs) pioglitazone and rosiglitazone are insulin-sensitizing PPARgamma agonists used to treat type 2 diabetes (T2DM). Despite evidence for TZDs limiting inflammation and atherosclerosis, questions exist regarding differential responses to TZDs. In a double-blinded, placebo-controlled 16-week trial among recently diagnosed T2DM subjects (n = 34), pioglitazone-treated subjects manifested lower triglycerides and lacked the increase in soluble vascular cell adhesion molecules (sVCAM)-1 evident in the placebo group. Previously we reported PPARalpha but not PPARgamma agonists could repress VCAM-1 expression. Since both triglyceride-lowering and VCAM-1 repression characterize PPARalpha activation, we studied pioglitazone's effects via PPARalpha. METHODS: Pioglitazone effects on known PPARalpha responses--ligand binding domain activation and PPARalpha target gene expression--were tested in vitro and in vivo, including in wild-type and PPARalpha-deficient cells and mice, and compared with the effects of other PPARgamma (rosiglitazone) and PPARalpha (WY14643) agonists. RESULTS: Pioglitazone repressed endothelial TNFalpha-induced VCAM-1 messenger ribonucleic acid expression and promoter activity, and induced hepatic IkappaBalpha in a manner dependent on both pioglitazone exposure and PPARalpha expression. Pioglitazone also activated the PPARalpha ligand binding domain and induced PPARalpha target gene expression, with in vitro effects that were most pronounced in endothelial cells. In vivo, pioglitazone administration modulated sVCAM-1 levels and IkappaBalpha expression in wild-type but not PPARalpha-deficient mice. CONCLUSIONS: Pioglitazone regulates inflammatory target genes in hepatic (IkappaBalpha) and endothelial (VCAM-1) settings in a PPARalpha-dependent manner. These data offer novel mechanisms that may underlie distinct TZD responses.

Glitazones and the cardiovascular system.

PURPOSE OF REVIEW: To chart recent progress on molecular mechanisms of rosiglitazone and pioglitazone in the cardiovascular system. RECENT FINDINGS: Several classes of oral antidiabetic drugs are available to treat type 2 diabetes, but glitazones offer the unique promise of insulin-sensitizing ability coupled with potential to reverse cardiovascular abnormalities associated with insulin resistance. Currently the two drugs used are rosiglitazone and pioglitazone, marketed as Avandia and Actos. Recent results of different metaanalyses were inconclusive as to whether rosiglitazone caused real adverse effects of myocardial ischemia. Thus, the US Food and Drugs Administration placed a black box warning on Avandia to signal potential of myocardial infarction and heart-related deaths, as a precautionary measure until analyses of all available data provide clarity. Also unresolved is the extent to which the two compounds share modes of action. SUMMARY: Type II diabetes affects more than 160 million people, approximately 5% of the world's population (http://www.who.org). Recently, questions have been raised about the cardiovascular safety of glitazone antidiabetic drugs. Clearly, there is an urgency to define molecular mechanisms of rosiglitazone and pioglitazone and understand how these drugs may impact patients.

Predisposition to colorectal cancer in rats with resolved colitis: role of cyclooxygenase-2-derived prostaglandin d2.

Colitis markedly increases the risk of developing colon cancer, but the underlying mechanisms are not fully understood. In a rat model of colitis, alterations in epithelial secretion, proliferation, and barrier function persist long after healing has occurred. In the present study, we examined whether rats that have recovered from a bout of colitis are more susceptible to preneoplastic lesions and whether this susceptibility is mediated by cyclooxygenase (COX)-2-derived prostaglandin (PG) D2. Colitis was induced by intracolonic administration of trinitrobenzenesulfonic acid. Six weeks later, weekly treatment with the carcinogen azoxymethane was initiated. Postcolitis rats exhibited significantly more aberrant crypt foci after azoxymethane treatment than controls. The postcolitis rats also exhibited markedly increased colonic PGD2 synthesis and elevated COX-2, H-PGD synthase, and beta-catenin expression. Treatment for 1 week with a selective COX-2 inhibitor or with a selective PGD2 receptor (DP1) antagonist significantly reduced susceptibility of postcolitis rats to aberrant crypt foci development, beta-catenin expression, and mucosal thickness. The results from this animal model suggest that prolonged elevation of COX-2-derived PGD2 synthesis after resolution of colitis may contribute significantly to colitis-associated increases in colon cancer incidence. PGD2 may therefore represent a rational target for therapies directed at reducing the incidence of colitis-associated colorectal cancer.

Lipoxin agonists: turn right! to path of resolving neutrophil.

An impressive array of cellular and molecular adaptive responses achieves homeostasis. The inflammatory reaction is an adaptive response triggered by an insult to culminate into the overt cardinal signs of inflammation, eventually leading to resolution and returning the organism back to its original centered state. This article focuses on some aspects of the lipoxin A4 signaling pathway during the resolution phase, to better understand molecular mechanisms by which a neutrophil directs an inflammatory reaction to switch off and resume homeostasis. Defining the resolution state of a neutrophil at the molecular level will aid in treatments of diseases that are associated with an exaggerated and uncontrolled inflammation.

Emerging roles for cyclooxygenase-2 in gastrointestinal mucosal defense.

The development of selective inhibitors of cyclooxygenase-2 (COX-2) was based on the concept that this enzyme played little, if any, role in modulating the ability of the gastrointestinal (GI) tract to resist and respond to injury. There is now overwhelming evidence that this is far from true. Indeed, COX-2 mediates several of the most important components of 'mucosal defense', contributes significantly to the resolution of GI inflammation and plays a crucial role in regulating ulcer healing. COX-2 also contributes to long-term changes in GI function after bouts of inflammation.

Lipoxin agonists: turn right! to path of resolving neutrophil

An impressive array of cellular and molecular adaptive responses achieves homeostasis. The inflammatory reaction is an adaptive response triggered by an insult to culminate into the overt cardinal signs of inflammation, eventually leading to resolution and returning the organism back to its original centered state. This article focuses on some aspects of the lipoxin A4 signaling pathway during the resolution phase, to better understand molecular mechanisms by which a neutrophil directs an inflammatory reaction to switch off and resume homeostasis. Defining the resolution state of a neutrophil at the molecular level will aid in treatments of diseases that are associated with an exaggerated and uncontrolled inflammation.

A synthetic eicosanoid LX-mimetic unravels host-donor interactions in allogeneic BMT-induced GvHD to reveal an early protective role for host neutrophils.

Lipoxin A(4) (LXA(4)) and aspirin-triggered 15-epi-LXA(4) are potent endogenous lipid mediators thought to define the inflammatory set-point. We used single prophylactic administrations of a synthetic aspirin-triggered lipoxin A(4) signal mimetic, ATLa, to probe dynamics of early host-donor interactions in a mouse model for the inflammation-associated multifactorial disease of allogeneic bone marrow transplant (BMT) -induced graft-vs.-host disease (GvHD). We first demonstrated that both host and donor are responsive to the ATLa signals. The simple and restricted regimen of a single prophylactic administration of ATLa [100 ng/mL to donor cells or 1 microg (approximately 50 microg/kg) i.v. to host] was sufficient to delay death. Clinical indicators of weight, skin lesions, diarrhea and eye inflammation were monitored. Histological analyses on day 45 post-BMT showed that the degree of cellular trafficking, particularly neutrophil infiltrate, and protection of end-organ target pathology are different, depending on whether the host or donor was treated with ATLa. Taken together, these results chart some ATLa protective effects on GvHD cellular dynamics over time and identify a previously unrecognized effect of host neutrophils in the early phase post-BMT as important determinants in the dynamics of GvHD onset and progression.-Devchand, P. R., Schmidt, B. A., Primo, V. C., Zhang, Q.-y., Arnaout, M. A., Serhan, C. N., Nikolic, B. A synthetic eicosanoid LX-mimetic unravels host-donor interactions in allogeneic BMT-induced GvHD to reveal an early protective role for host neutrophils.

Lipoxins and novel 15-epi-lipoxin analogs display potent anti-inflammatory actions after oral administration.

1. Lipoxins (LX) and aspirin-triggered 15-epi-lipoxins (ATL) exert potent anti-inflammatory actions. In the present study, we determined the anti-inflammatory efficacy of endogenous LXA(4) and LXB(4), the stable ATL analog ATLa2, and a series of novel 3-oxa-ATL analogs (ZK-996, ZK-990, ZK-994, and ZK-142) after intravenous, oral, and topical administration in mice. 2. LXA(4), LXB(4), ATLa2, and ZK-994 were orally active, exhibiting potent systemic inhibition of zymosan A-induced peritonitis at very low doses (50 ng kg(-1)-50 microg kg(-1)). 3. Intravenous ZK-994 and ZK-142 (500 microg kg(-1)) potently attenuated hind limb ischemia/reperfusion-induced lung injury, with 32+/-12 and 53+/-5% inhibition (P<0.05), respectively, of neutrophil accumulation in lungs. The same dose of ATLa2 had no significant protective action. 4. Topical application of ATLa2, ZK-994, and ZK-142 ( approximately 20 microg cm(-2)) prevented vascular leakage and neutrophil infiltration in LTB(4)/PGE(2)-stimulated ear skin inflammation. While ATLa2 and ZK-142 displayed approximately equal anti-inflammatory efficacy in this model, ZK-994 displayed a slower onset of action. 5. In summary, native LXA(4) and LXB(4), and analogs ATLa2, ZK-142, and ZK-994 retain broad anti-inflammatory effects after intravenous, oral, and topical administration. The 3-oxa-ATL analogs, which have enhanced metabolic and chemical stability and a superior pharmacokinetic profile, provide new opportunities to explore the actions and therapeutic potential for LX and ATL.

Lipoxins and aspirin-triggered lipoxins in airway responses.

Here, we have demonstrated potent inhibition of allergen-mediated pulmonary inflammation and airway hyper-responsiveness by a novel dual-pronged action of LX's. Moreover, these results indicate that LX's play pivotal and previously unappreciated roles in regulating allergy and pulmonary inflammation.

Human ALX receptor regulates neutrophil recruitment in transgenic mice: roles in inflammation and host defense.

Signaling pathways instrumental in the temporal and spatial progression of acute inflammation toward resolution are of wide interest. Here a transgenic mouse with myeloid-selective expression of human lipoxin A4 receptor (hALX) was prepared and used to evaluate in vivo the effect of hALX expression. hALX-transfected HEK293 cells transmitted LXA4 signals that inhibit TNFalpha-induced NFkappaB activation. Transgenic FvB mice were generated by DNA injections of a 3.8 kb transgene consisting of the full-length hALX cDNA driven by a fragment of the hCD11b promoter. When topically challenged via dermal ear skin, hALX transgenic mice gave attenuated neutrophil infiltration (approximately 80% reduction) in response to leukotriene B4 (LTB4) plus prostaglandin E2 (PGE2) as well as approximately 50% reduction in PMN infiltrates (P<0.02) to receptor-bypass inflammation evoked by phorbol ester. The hALX transgenic mice gave markedly decreased PMN infiltrates to the peritoneum with zymosan and altered the dynamics of this response. Transgenic hALX mice displayed increased sensitivity with >50% reduction in PMN infiltrates to suboptimal doses (10 ng/mouse) of the ligand lipoxin A4 stable analog compared with <10% reduction of PMN in nontransgenic littermates. Soluble mediators generated within the local inflammatory milieu of hALX mice showed diminished ability to activate the proinflammatory transcription factor NFkappaB. Analyses of the lipid-derived mediators from exudates using LC-MS tandem mass spectroscopy indicated an altered profile in hALX transgenic mice that included lower levels of LTB4 and increased amounts of lipoxin A4 compared with nontransgenic littermates. Together these results demonstrate a gain-of-function with hALX transgenic mouse and indicate that ALX is a key receptor and sensor in formation of acute exudates and their resolution.

Novel docosatrienes and 17S-resolvins generated from docosahexaenoic acid in murine brain, human blood, and glial cells. Autacoids in anti-inflammation.

Docosahexaenoic acid (DHA, C22:6) is highly enriched in brain, synapses, and retina and is a major omega-3 fatty acid. Deficiencies in this essential fatty acid are reportedly associated with neuronal function, cancer, and inflammation. Here, using new lipidomic analyses employing high performance liquid chromatography coupled with a photodiode-array detector and a tandem mass spectrometer, a novel series of endogenous mediators was identified in blood, leukocytes, brain, and glial cells as 17S-hydroxy-containing docosanoids denoted as docosatrienes (the main bioactive member of the series was 10,17S-docosatriene) and 17S series resolvins. These novel mediators were biosynthesized via epoxide-containing intermediates and proved potent (pico- to nanomolar range) regulators of both leukocytes reducing infiltration in vivo and glial cells blocking their cytokine production. These results indicate that DHA is the precursor to potent protective mediators generated via enzymatic oxygenations to novel docosatrienes and 17S series resolvins that each regulate events of interest in inflammation and resolution.

Resolvins: a family of bioactive products of omega-3 fatty acid transformation circuits initiated by aspirin treatment that counter proinflammation signals.

Aspirin (ASA) is unique among current therapies because it acetylates cyclooxygenase (COX)-2 enabling the biosynthesis of R-containing precursors of endogenous antiinflammatory mediators. Here, we report that lipidomic analysis of exudates obtained in the resolution phase from mice treated with ASA and docosahexaenoic acid (DHA) (C22:6) produce a novel family of bioactive 17R-hydroxy-containing di- and tri-hydroxy-docosanoids termed resolvins. Murine brain treated with aspirin produced endogenous 17R-hydroxydocosahexaenoic acid as did human microglial cells. Human COX-2 converted DHA to 13-hydroxy-DHA that switched with ASA to 17R-HDHA that also proved a major route in hypoxic endothelial cells. Human neutrophils transformed COX-2-ASA-derived 17R-hydroxy-DHA into two sets of novel di- and trihydroxy products; one initiated via oxygenation at carbon 7 and the other at carbon 4. These compounds inhibited (IC(50) approximately 50 pM) microglial cell cytokine expression and in vivo dermal inflammation and peritonitis at ng doses, reducing 40-80% leukocytic exudates. These results indicate that exudates, vascular, leukocytes and neural cells treated with aspirin convert DHA to novel 17R-hydroxy series of docosanoids that are potent regulators. These biosynthetic pathways utilize omega-3 DHA and EPA during multicellular events in resolution to produce a family of protective compounds, i.e., resolvins, that enhance proresolution status.

Multi-pronged inhibition of airway hyper-responsiveness and inflammation by lipoxin A(4).

The prevalence of asthma continues to increase and its optimal treatment remains a challenge. Here, we investigated the actions of lipoxin A(4) (LXA(4)) and its leukocyte receptor in pulmonary inflammation using a murine model of asthma. Allergen challenge initiated airway biosynthesis of LXA(4) and increased expression of its receptor. Administration of a stable analog of LXA(4) blocked both airway hyper-responsiveness and pulmonary inflammation, as shown by decreased leukocytes and mediators, including interleukin-5, interleukin-13, eotaxin, prostanoids and cysteinyl leukotrienes. Moreover, transgenic expression of human LXA(4) receptors in murine leukocytes led to significant inhibition of pulmonary inflammation and eicosanoid-initiated eosinophil tissue infiltration. Inhibition of airway hyper-responsiveness and allergic airway inflammation with a stable LXA(4) analog highlights a unique counter-regulatory profile for the LXA(4) system and its leukocyte receptor in airway responses. Moreover, our findings suggest that lipoxin and related pathways offer novel multi-pronged therapeutic approaches for human asthma.