Coordination of hypothalamic and pituitary T3 production regulates TSH expression

Type II deiodinase (D2) activates thyroid hormone by converting thyroxine (T4) to 3,5,3′-triiodothyronine (T3). This allows plasma T4 to signal a negative feedback loop that inhibits production of thyrotropin-releasing hormone (TRH) in the mediobasal hypothalamus (MBH) and thyroid-stimulating hormone (TSH) in the pituitary. To determine the relative contributions of these D2 pathways in the feedback loop, we developed 2 mouse strains with pituitary- and astrocyte-specific D2 knockdown (pit-D2 KO and astro-D2 KO mice, respectively). The pit-D2 KO mice had normal serum T3 and were systemically euthyroid, but exhibited an approximately 3-fold elevation in serum TSH levels and a 40% reduction in biological activity. This was the result of elevated serum T4 that increased D2-mediated T3 production in the MBH, thus decreasing Trh mRNA. That tanycytes, not astrocytes, are the cells within the MBH that mediate T4-to-T3 conversion was defined by studies using the astro-D2 KO mice. Despite near-complete loss of brain D2, tanycyte D2 was preserved in astro-D2 KO mice at levels that were sufficient to maintain both the T4-dependent negative feedback loop and thyroid economy. Taken together, these data demonstrated that the hypothalamic-thyroid axis is wired to maintain normal plasma T3 levels, which is achieved through coordination of T4-to-T3 conversion between thyrotrophs and tanycytes.     

Matrix engineering.

Matrix engineering is a technology that utilizes hyaluronan (HA, hyaluronic acid) based matrices to control, direct or augment tissue regenerative processes. Hyaluronan and the concept of matrix engineering have become established tools in ophthalmic and orthopaedic medicine. The clinical indications for HA are limited by the physical properties and short residence time of the natural HA molecule. To expand and improve upon its current medical applications, a family of HA derivatives was prepared by chemical modification and cross-linking. Relative to the non-modified HA molecule, the hylan family of polymers provides more versatile physical forms, improved mechanical properties and an extended residence time. Hylan can also be used as a surface coating to improve blood compatibility. The chemical, physical and biological properties of hylans will be reviewed, focusing on the specific therapeutic indications they enable.     

Arsenate reduction in human erythrocytes and rats--testing the role of purine nucleoside phosphorylase.

Reduction of the pentavalent arsenate (AsV) to the thiol-reactive arsenite (AsIII) toxifies this environmentally prevalent form of arsenic, yet its biochemical mechanism in mammals is incompletely understood. Purine nucleoside phosphorylase (PNP) has been shown recently to function as an AsV reductase in vitro, provided its substrate (inosine or guanosine) and an appropriate dithiol (e.g., dithiothreitol, DTT) were present. It was of interest to know if this ubiquitous enzyme played a significant role in reduction of AsV to AsIII in vivo. Two approaches were used to test this. First, it was determined if compounds that influenced AsV reduction by purified PNP (i.e., nucleosides, thiols, and PNP inhibitors) would similarly affect reduction of AsV by human erythrocytes. Erythrocytes were incubated with AsV, and the formed AsIII was quantified by HPLC-hydride generation-atomic fluorescence spectrometry. The red blood cells reduced AsV at a considerable rate, which could be enhanced by inosine or inosine plus DTT. These stimulated AsIII formation rates were PNP-dependent, as PNP inhibitors strongly inhibited them. In contrast, PNP inhibitors had little if any inhibitory effect on AsIII formation in the absence of exogenous inosine, indicating that this basal rate of AsV reduction is PNP-independent. Second, the role of PNP in reduction of AsV in vivo was also assessed by investigating the effect of the PNP inhibitor BCX-1777 on the biotransformation of AsV in control and DTT-treated rats with cannulated bile duct and ligated renal pedicles. Although it abolished hepatic PNP activity, BCX-1777 influenced neither the biliary excretion of AsIII and monomethylarsonous acid, nor the tissue concentration of AsV and its metabolites in either group of AsV-injected rats. Thus, despite its in vitro activity, PNP does not appear to play a significant role in AsV reduction in human erythrocytes and in rats in vivo. Further research should clarify the in vivo relevant mechanisms of AsV reduction in mammals.     

Do Patients Regret Having Received Systemic Treatment for Advanced Non-Small Cell Lung Cancer: A Prospective Evaluation

BackgroundThousands of patients annually receive treatment for advanced non‐small cell lung cancer (NSCLC), but little is known about their views on the decision to receive that treatment, or regret. This trial prospectively evaluated the incidence of regret and whether baseline characteristics, patient decision‐making parameters, or clinical progress early in the treatment course predicts regret.Materials and MethodsPatients receiving systemic treatment for advanced NSCLC completed every 3‐week patient reported outcome (PRO) assessment using the electronic Lung Cancer Symptom Scale (eLCSS‐QL), including the 3‐Item Global Index (3‐IGI; assessing overall distress, activities, and quality of life [QL]). A prespecified secondary aim was to determine the frequency of regret evaluated at 3 months after starting treatment. Patients were randomized to usual care or enhanced care (which included use of the DecisionKEYS decision aid).ResultsOf 164 patients entered, 160 received treatment and 142 were evaluable for regret. In total, 11.5% of patients and 9% of their supporters expressed regret. Baseline characteristics did not predict regret; regret was rarely expressed by those who had a less than 20% decline or improvement in the 3‐IGI PRO score after two treatment cycles. In contrast, when asked if they would make the same decision again, only 1% not having a 20% 3‐IGI decline expressed regret, versus 14% with a 3‐IGI decline (p = .01).ConclusionThe majority of patients having regret were identified early using the PRO 3‐IGI of the eLCSS‐QL measure. Identifying patients at risk for regret allows for interventions, including frank discussions of progress and goals early in the treatment course, which could address regret in patients and their supporters.Implications for PracticeThis report documents prospectively, for the first time, the incidence of treatment‐related regret in patients with advanced lung cancer and outlines that risk of regret is associated with patient‐determined worsening health status early in the course of treatment. Identifying patients at risk for regret early in treatment (before the third cycle of treatment) appears to be crucial. Counseling at that time should include a discussion of consideration of treatment change and the reason for this change.     

The evidence for and against different modes of tumour cell extravasation in the lung: diapedesis,capillary destruction,necroptosis, and endothelialization

The development of lung metastasis is a significant negative prognostic factor for cancer patients. The extravasation phase of lung metastasis involves interactions of tumour cells with the pulmonary endothelium. These interactions may have broad biological and medical significance, with potential clinical implications ranging from the discovery of lung metastasis biomarkers to the identification of targets for intervention in preventing lung metastases. Because of the potential significance, the mechanisms of tumour cell extravasation require cautious, systematic studies. Here, we discuss the literature pertaining to the proposed mechanisms of extravasation and critically compare a recently proposed mechanism (tumour cell‐induced endothelial necroptosis) with the already described extravasation mechanisms in the lung. We also provide novel data that may help to explain the underlying physiological basis for endothelialization as a mechanism of tumour cell extravasation in the lung. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.