RAGE Deficiency Improves Postinjury Sciatic Nerve Regeneration in Type 1 Diabetic Mice

Peripheral neuropathy and insensate limbs and digits cause significant morbidity in diabetic individuals. Previous studies showed that deletion of the receptor for advanced end-glycation products (RAGE) in mice was protective in long-term diabetic neuropathy. Here, we tested the hypothesis that RAGE suppresses effective axonal regeneration in superimposed acute peripheral nerve injury attributable to tissue-damaging inflammatory responses. We report that deletion of RAGE, particularly in diabetic mice, resulted in significantly higher myelinated fiber densities and conduction velocities consequent to acute sciatic nerve crush compared with wild-type control animals. Consistent with key roles for RAGE-dependent inflammation, reconstitution of diabetic wild-type mice with RAGE-null versus wild-type bone marrow resulted in significantly improved axonal regeneration and restoration of function. Diabetic RAGE-null mice displayed higher numbers of invading macrophages in the nerve segments postcrush compared with wild-type animals, and these macrophages in diabetic RAGE-null mice displayed greater M2 polarization. In vitro, treatment of wild-type bone marrow–derived macrophages with advanced glycation end products (AGEs), which accumulate in diabetic nerve tissue, increased M1 and decreased M2 gene expression in a RAGE-dependent manner. Blockade of RAGE may be beneficial in the acute complications of diabetic neuropathy, at least in part, via upregulation of regeneration signals.Diabetes leads to the development of multiple complications (1–3). Peripheral neuropathy affects 30–50% of all diabetic patients (4–6). Individuals with diabetes are more vulnerable to superimposed thermal and pressure injuries (7–10). Diabetic individuals exposed to either topical application of capsaicin or intracutaneous excision axotomy (punch skin biopsy) displayed a reduction in regenerative rate, even without evidence of neuropathy, and reduced axonal regenerative sprouting and blood vessel growth, respectively, compared with nondiabetic control subjects (11,12). Studies of diabetic animals reported a delay of axonal regeneration after acute sciatic nerve crush compared with nondiabetic mice (13). Evidence suggests that enhanced accumulation of advanced glycation end products (AGEs) may be an important contributing mechanism to the pathogenesis of diabetes complications (14,15). AGEs are a heterogeneous group of molecules that impact cellular properties and gene expression via specific receptors such as receptor for advanced end-glycation product (RAGE) (16–18). RAGE, a pattern recognition receptor, also interacts with multiple members of the proinflammatory S100/calgranulin family and with high-mobility group box 1 protein (HMGB1); both classes of molecules are implicated in inflammation and cellular migration (19,20). These non-AGE ligands may be released by dying cells, and evidence suggests that although RAGE is not intimately involved in innate immune responses, its upregulation and activation by these ligands contribute to sustained inflammation and suppression of repair (21,22).These considerations prompted us to hypothesize that RAGE action in superimposed acute injury to the peripheral nerve, particularly in diabetes, attenuates neurite outgrowth and axonal regeneration via tissue-damaging inflammatory mechanisms. We subjected wild-type (WT) and homozygous RAGE-null mice to acute sciatic nerve crush to dissect the specific contribution of bone marrow RAGE expression. We also subjected WT mice to lethal irradiation and performed reconstitution with bone marrow expressing or devoid of RAGE.     

Effects of Atrial Natriuretic Peptide After Prolonged Hypothermic Storage of the Isolated Rat Heart

Primary graft failure (PGF) caused by ischemia‐reperfusion injury (IRI) is the strongest determinant of perioperative mortality after heart transplantation. Atrial natriuretic peptide (ANP) has been found to reduce the IRI of cardiomyocytes and may be beneficial in alleviating PGF after heart transplantation, although there is a lack of evidence to support this issue. The purpose of this study was to investigate the cardioprotective effects of ANP after prolonged hypothermic storage. For this purpose, an isolated working‐heart rat model was used. After the preparation, the hearts were arrested with and stored in an extracellular‐based cardioplegic solution at 3–4°C for 6 h and followed by 25 min of reperfusion. The hearts were divided into four groups (n = 7 in each group) according to the timing of ANP administration: Group 1 (in perfusate before storage), Group 2 (in cardioplegia), Group 3 (in reperfusate), and control (no administration of ANP). Left ventricular functional recovery and the incidence of ventricular fibrillation (VF) were compared. ANP administration at the time of reperfusion improved the percent recovery of left ventricular developed pressure (control, 45.5 ± 10.2; Group 1, 47.4 ± 8.8; Group 2, 45.3 ± 12 vs. Group 3, 76.3 ± 7; P < 0.05) and maximum first derivative of the left ventricular pressure (control, 47.9 ± 8.7; Group 1, 46.7 ± 8.8; Group 2, 49.6 ± 10.8 vs. Group 3, 76.6 ± 7.5; P < 0.05). The incidence of VF after reperfusion did not differ significantly among these four groups (71.4, 85.7, 57.1, and 85.7% in Groups 1, 2, 3, and control, respectively). This result suggests that the administration of ANP at the time of reperfusion may have the potential to decrease the incidence of PGF after heart transplantation.     

Juvenile polyposis, hereditary hemorrhagic telangiectasia, and early onset colorectal cancer in patients with SMAD4 mutation

Background

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder most often caused by mutation in the endoglin or ALK1 genes. A distinct syndrome combines the clinical features of HHT and juvenile polyposis (JP) and has been associated with SMAD4 mutation. The aim of this study was to describe the phenotype of patients with JP–HHT and SMAD4 mutations and to compare this phenotype with HHT or JP patients with mutations other than SMAD4.

Methods

Patients prospectively enrolled in the Toronto HHT and JP databases who underwent genotyping were included. The phenotypic characteristics of JP–HHT patients with SMAD4 mutations and patients with mutations other than SMAD4 were analyzed and compared.

Results

Three hundred and fifty-eight patients underwent genetic testing (HHT, n?=?332; JP, n?=?26). Among fourteen patients identified with SMAD4 mutations, ten met the clinical diagnostic criteria for both JP and HHT (71%). Patients with SMAD4 mutations had 100% penetrance of the polyposis phenotype. All patients with JP and SMAD4 mutation had features of HHT. Three JP–HHT patients developed early onset colorectal cancer (CRC) (mean age 28 years). JP–HHT patients with SMAD4 mutation had a significantly higher rate of anemia than HHT patients with mutations other than SMAD4.

Conclusions

Patients with HHT and SMAD4 mutations are at significant risk of JP and CRC. The gastrointestinal phenotype is similar to JP patients without SMAD4 mutation. It is essential for HHT patients to undergo genetic testing to determine if they have SMAD4 mutations so that appropriate gastrointestinal screening and surveillance for JP and CRC can be completed.     

50th anniversary of the discovery of ibuprofen: an interview with Dr Stewart Adams

2011 marks the 50th anniversary of the discovery of ibuprofen. This article is a focus on the personal reflections and career of Dr Stewart Adams OBE, the scientist whose research lead to the discovery of the cyclooxygenase inhibitor. When Dr Adams discovered ibuprofen, he was working as a pharmacologist in the Research Department for the Boots Pure Drug Company Ltd. Dr Adams was assigned to work on rheumatoid arthritis (RA) and chose in 1953 to search for a drug that would be effective in RA but would not be a corticosteroid. He was one of the first workers in this field that later became known as NSAIDs (Non-Steroidal Anti Inflammatory Drugs). In 1961, Dr Adams with John Nicholson, the organic chemist, filed a patent for the compound 2-(4-isobutylphenyl) propionic acid, later to become one of the most successful NSAIDs in the modern world, ibuprofen. In this article, Dr Adams gives his modest insight into the early stages and initial observations which led to this world-wide success.     

Impaired regulatory T cell reconstitution in patients with acute graft-versus-host disease and cytomegalovirus infection after allogeneic bone marrow transplantation

To elucidate the correlation between regulatory T cells (Tregs) and acute graft-versus-host disease (aGVHD) or cytomegalovirus infection following allogeneic bone marrow transplantation (allo-BMT), we evaluated either CD4?CD25(high) or FOXP3? Treg-enriched cells in peripheral blood (PB) from 20 patients who received allo-BMT, and in biopsies of skin with aGVHD. Proportions of CD4?CD25(high)FOXP3? cells in total lymphocytes, but not other types of T cells, were lower in patients who eventually developed grades II-IV aGVHD (n = 13) than in others (n = 7, P < 0.001). Proportions of CD62L? cells in CD4?CD25(high) cells at day +30 were lower (P < 0.01) in patients who eventually showed cytomegalovirus viremia (n = 6) than in others (n = 14). Incidence of aGVHD (P < 0.05) or cytomegalovirus viremia (P < 0.05) was higher in patients without these complications, but with lower proportions of PB CD4?CD25(high)FOXP3? cells at day +30 (n = 8) than in others (n = 8). However, in skin with aGVHD (n = 5), there was marked or slightly increased infiltration of CD8? cells (P < 0.001) or CD3?FOXP3? cells (P < 0.05), respectively, when compared with control (n = 5), resulting in threefold higher ratio of CD8?/CD3?FOXP3? cells in aGVHD relative to controls (P < 0.05). Thus, impaired reconstitution of Tregs may be associated with aGVHD and CMV infection. Moreover, imbalance of Tregs and CD8? cells may play a role in aGVHD tissue.