Connexins Biology in the Pathophysiology of Retinal Diseases

Connexins (Cx) are a family of transmembrane proteins that form gap junction intercellular channels that connect neighboring cells. These channels allow the passage of ions and other biomolecules smaller than 1 kDa, thereby synchronizing the cells both electrically and metabolically. Cxs are expressed in all retinal cell types and the diversity of Cx isoforms involved in the assembly of the channels provides a functional syncytium required for visual transduction. In this chapter, we summarize the status of current knowledge regarding Cx biology in retinal tissues and discuss how Cx dysfunction is associated with retinal disease pathophysiology. Although the contribution of Cx deficiency to retinal degeneration is not well understood, recent findings present Cx as a potential therapeutic target. Therefore, we will briefly discuss pharmacological approaches and gene therapies that are being explored to modulate Cx function and fight sight-threatening eye diseases.

Autophagy and Glycative Stress: A Bittersweet Relationship in Neurodegeneration

Autophagy is a fine-tuned proteolytic pathway that moves dysfunctional/aged cellular components into the lysosomal compartment for degradation. Over the last 3 decades, global research has provided evidence for the protective role of autophagy in different brain cell components. Autophagic capacities decline with age, which contributes to the accumulation of obsolete/damaged organelles and proteins and, ultimately, leads to cellular aging in brain tissues. It is thus well-accepted that autophagy plays an essential role in brain homeostasis, and malfunction of this catabolic system is associated with major neurodegenerative disorders. Autophagy function can be modulated by different types of stress, including glycative stress. Glycative stress is defined as a cellular status with abnormal and accelerated accumulation of advanced glycation end products (AGEs). It occurs in hyperglycemic states, both through the consumption of high-sugar diets or under metabolic conditions such as diabetes. In recent years, glycative stress has gained attention for its adverse impact on brain pathology. This is because glycative stress stimulates insoluble, proteinaceous aggregation that is linked to the malfunction of different neuropathological proteins. Despite the emergence of new literature suggesting that autophagy plays a major role in fighting glycation-derived damage by removing cytosolic AGEs, excessive glycative stress might also negatively impact autophagic function. In this mini-review, we provide insight on the status of present knowledge regarding the role of autophagy in brain physiology and pathophysiology, with an emphasis on the cytoprotective role of autophagic function to ameliorate the adverse effects of glycation-derived damage in neurons, glia, and neuron-glia interactions.

Defective recruitment of motor proteins to autophagic compartments contributes to autophagic failure in aging

Inability to preserve proteostasis with age contributes to the gradual loss of function that characterizes old organisms. Defective autophagy, a component of the proteostasis network for delivery and degradation of intracellular materials in lysosomes, has been described in multiple old organisms, while a robust autophagy response has been linked to longevity. The molecular mechanisms responsible for defective autophagic function with age remain, for the most part, poorly characterized. In this work, we have identified differences between young and old cells in the intracellular trafficking of the vesicular compartments that participate in autophagy. Failure to reposition autophagosomes and lysosomes toward the perinuclear region with age reduces the efficiency of their fusion and the subsequent degradation of the sequestered cargo. Hepatocytes from old mice display lower association of two microtubule-based minus-end-directed motor proteins, the well-characterized dynein, and the less-studied KIFC3, with autophagosomes and lysosomes, respectively. Using genetic approaches to mimic the lower levels of KIFC3 observed in old cells, we confirmed that reduced content of this motor protein in fibroblasts leads to failed lysosomal repositioning and diminished autophagic flux. Our study connects defects in intracellular trafficking with insufficient autophagy in old organisms and identifies motor proteins as a novel target for future interventions aiming at correcting autophagic activity with anti-aging purposes.

Activation of the Anti-Aging and Cognition-Enhancing Gene Klotho by CRISPR-dCas9 Transcriptional Effector Complex

Multiple lines of evidence show that the anti-aging and cognition-enhancing protein Klotho fosters neuronal survival, increases the anti-oxidative stress defense, and promotes remyelination of demyelinated axons. Thus, upregulation of the Klotho gene can potentially alleviate the symptoms and/or prevent the progression of age-associated neurodegenerative diseases such as Alzheimer's disease and demyelinating diseases such as multiple sclerosis. Here we used a CRISPR-dCas9 complex to investigate single-guide RNA (sgRNA) targeting the Klotho promoter region for efficient transcriptional activation of the Klotho gene. We tested the sgRNAs within the - 1 to - 300 bp of the Klotho promoter region and identified two sgRNAs that can effectively enhance Klotho gene transcription. We examined the transcriptional activation of the Klotho gene using three different systems: a Firefly luciferase (FLuc) and NanoLuc luciferase (NLuc) coincidence reporter system, a NLuc knock-in in Klotho 3'-UTR using CRISPR genomic editing, and two human cell lines: neuronal SY5Y cells and kidney HK-2 cells that express Klotho endogenously. The two sgRNAs enhanced Klotho expression at both the gene and protein levels. Our results show the feasibility of gene therapy for targeting Klotho using CRISPR technology. Enhancing Klotho levels has a therapeutic potential for increasing cognition and treating age-associated neurodegenerative, demyelinating and other diseases, such as chronic kidney disease and cancer.

SF3B1/Hsh155 HEAT motif mutations affect interaction with the spliceosomal ATPase Prp5, resulting in altered branch site selectivity in pre-mRNA splicing

Mutations in the U2 snRNP component SF3B1 are prominent in myelodysplastic syndromes (MDSs) and other cancers and have been shown recently to alter branch site (BS) or 3' splice site selection in splicing. However, the molecular mechanism of altered splicing is not known. We show here that hsh155 mutant alleles in Saccharomyces cerevisiae, counterparts of SF3B1 mutations frequently found in cancers, specifically change splicing of suboptimal BS pre-mRNA substrates. We found that Hsh155p interacts directly with Prp5p, the first ATPase that acts during spliceosome assembly, and localized the interacting regions to HEAT (Huntingtin, EF3, PP2A, and TOR1) motifs in SF3B1 associated with disease mutations. Furthermore, we show that mutations in these motifs from both human disease and yeast genetic screens alter the physical interaction with Prp5p, alter branch region specification, and phenocopy mutations in Prp5p. These and other data demonstrate that mutations in Hsh155p and Prp5p alter splicing because they change the direct physical interaction between Hsh155p and Prp5p. This altered physical interaction results in altered loading (i.e., "fidelity") of the BS-U2 duplex into the SF3B complex during prespliceosome formation. These results provide a mechanistic framework to explain the consequences of intron recognition and splicing of SF3B1 mutations found in disease.

Autophagy modulates dynamics of connexins at the plasma membrane in a ubiquitin-dependent manner

Connexins modulate intercellular communication when assembled in gap junctions. Compromised macroautophagy increases cellular communication due to failure to degrade connexins at gap junctions. Nedd4-mediated ubiquitinylation of the connexin molecule is required to trigger its autophagy-dependent internalization and degradation.

Different pathways contribute to the turnover of connexins, the main structural components of gap junctions (GJs). The cellular pool of connexins targeted to each pathway and the functional consequences of degradation through these degradative pathways are unknown. In this work, we focused on the contribution of macroautophagy to connexin degradation. Using pharmacological and genetic blockage of macroautophagy both in vitro and in vivo, we found that the cellular pool targeted by this autophagic system is primarily the one organized into GJs. Interruption of connexins' macroautophagy resulted in their retention at the plasma membrane in the form of functional GJs and subsequent increased GJ-mediated intercellular diffusion. Up-regulation of macroautophagy alone is not sufficient to induce connexin internalization and degradation. To better understand what factors determine the autophagic degradation of GJ connexins, we analyzed the changes undergone by the fraction of plasma membrane connexin 43 targeted for macroautophagy and the sequence of events that trigger this process. We found that Nedd4-mediated ubiquitinylation of the connexin molecule is required to recruit the adaptor protein Eps15 to the GJ and to initiate the autophagy-dependent internalization and degradation of connexin 43. This study reveals a novel regulatory role for macroautophagy in GJ function that is directly dependent on the ubiquitinylation of plasma membrane connexins.

Spinal anesthesia for emergency abdominal surgery in uncontrolled hyperthyroidism

Patients with uncontrolled hyperthyroidism presenting as an emergency are at considerable risk. The anesthetic management of a thyrotoxic patient undergoing incidental emergency surgery is discussed. We focus on the intraoperative problems and, above all, postoperative pain management with regional anesthesia.

[Acute pain in "Don Quixote"]

OBJECTIVE

A descriptive analysis of references to pain symptoms in Don Quixote based on linguistic, literary, clinical, and mannerist features.

METHODS AND MATERIAL

Don Quixote was read and an entry was created for each description of an injury or illness (group I/I). A second group of entries was created for each medical commentary (group C). This information was complemented using a computer search for the roots of words referring to pain symptoms, with an asterisk placed after each root to locate all word forms used. Data entries with pain references were analyzed in group I/I by examining patient, location, characteristics, causes, associated disorders, remedies, caregivers, and recovery times and in group C by examining the full text.

RESULTS

Ninety-one entries were made (64 in group I/I, 27 in group c). References to pain were found in 37 entries (29 in group I/I, 8 in group C). The most commonly used words came from the roots dol (the Spanish root for dolor, or pain, among other related words) (52) and moli (for forms related to Spanish idiomatic uses of molido, suggesting severe injury) (19). All pains were due to injuries. Forty-two occasions of injury (Don Quixote 14, Sancho 9, others 19) and 51 lesions (ribs 5, back 5, other 15, unspecified 26) were mentioned. Known remedies and caregivers of the period were described, but other invented ones were also present. Associated disorders were insomnia, anxiety, rage, melancholy, functional impotence and other sexual dysfunctions. Recovery times ranged from 0 to 8 days.

CONCLUSION

Pain references are subject to literary considerations. The style is simple and the descriptions are credible for the period depicted but do not meet clinical standards. Issues of current interest are treated: pain threshold and sensitivity, social influences, the placebo effect, and affective disorders.

Hodgkin's disease. Prognostic value of Gallium-67 scintigraphy

AIM

The aim of this study is to assess the clinical impact of gallium-67 scintigraphy, before and after treatment, in patients with Hodgkin's disease, and to compare the overall survival between the patients whose gallium studies after treatment were negative and those whose studies remained positive.

METHODS

We have studied 75 patients (40 women, 35 men) with Hodgkin's disease. All the patients underwent (67)Ga scintigraphy at the moment of the diagnosis (basal study) and in the case that basal study was positive (abnormal hyper-uptake focus) we performed follow-up studies after the treatment. We have calculated the overall survival among patients whose studies after treatment were negative (1(st) group) and those whose studies remained positive (2(nd) group) and between patients whose studies were negative at diagnosis (3(rd) group).

RESULTS

Gallium scintigraphy was positive at diagnosis in 47 patients (62.6%). In 39 of them we were able to perform the follow-up study after treatment. The follow-up study was negative in 31 patients while in 8 patients the gallium scintigraphy remained positive. The overall survival was significantly higher (p<0.001) in the 1(st) group compared with the 2(nd) group. The overall survival was higher in the 1(st) group compared with the 3(rd) but statistic significance level was not reached.

CONCLUSION

Our data suggest that: 1) in Hodgkin's disease (67)Ga scintigraphy is useful to establish the diagnosis of complete remission; 2) if the gallium scan remains positive after treatment, the prognosis of patients is worse than the prognosis of patients with a negative scan.

Pulmonary fibrosis induced by cyclophosphamide

OBJECTIVE

To report a case of pulmonary fibrosis resulting from use of cyclophosphamide as chemotherapy to treat a patient with breast cancer.

CASE SUMMARY

We describe the case of a 52-year-old woman with breast cancer who developed pulmonary fibrosis after four cycles of chemotherapy that included cyclophosphamide. Pulmonary function tests revealed the presence of a severe ventilatory restriction. The open lung biopsy revealed pulmonary fibrosis with vascular sclerosis and signs of pulmonary hypertension.

DISCUSSION

Cyclophosphamide is an alkylating agent that has been associated with interstitial pneumonia and pulmonary fibrosis. The frequency of these unwanted effects is <1%. The clinical picture consists of the progressive appearance of dyspnea and a non-productive cough that progresses to severe pulmonary insufficiency. The risk factors described for these complications have been the use of chemotherapy regimens that include other drugs with known pulmonary toxicities, the cumulative total dose, the addition of radiotherapy, and the use of high doses of cyclophosphamide.

CONCLUSIONS

Even though the frequency of pulmonary fibrosis in patients treated with cyclophosphamide-based chemotherapy regimens is low, the presence of dyspnea and an interstitial pattern in a patient makes it necessary to consider that possible drug toxicity. The open lung biopsy is the most accurate diagnostic technique for these cases. The discontinuation of cyclophosphamide and treatment with corticosteroids is usually followed by clinical recovery in approximately 50% of patients and, in some cases, reversal of the lung injury.

Long-term results after combined modality treatment for non-metastatic osteosarcoma

Since the introduction of multimodality treatment, the prognosis of patients with high-grade non-metastatic osteosarcoma has significantly improved. A retrospective review was performed to assess the long-term results of this approach in a single centre setting, and to investigate the impact of potential clinical prognostic factors. Between 1985 and 1993, 35 patients with stage II-A and II-B osteosarcoma underwent preoperative chemotherapy (high-dose methotrexate), wide surgery, and adjuvant chemotherapy (cisplatin-doxorubicin/bleo-mycin-cyclophosphamide-dactinomycin) (modified T-10A protocol). There were 19 males and 16 females. Median patient age was 17 y (range 12-42). Primary tumour sites were the extremities (83%) and axial bones (17%). In spite of an unfavourable grade 3-4 histologic response rate to high-dose methotrexate of 12%, 31 (88%) patients were able to undergo limb-sparing surgery and 28 (80%) were rendered disease free after the planned therapy. Median follow-up was 8 y. The actuarial overall survival and disease-free survival rates were 64% and 49% at 5 y, and 59% and 49% at 10 y, respectively. Tumour size and primary site were significant prognostic factors for survival in univariate analyses. In conclusion, long-term survival after combined modality treatment can be achieved in more than 60% of patients with localised osteosarcoma, including non-appendicular lesions. Limb-sparing surgery is a realistic goal for most cases. The prognostic value of tumour necrosis and the efficacy of neoadjuvant chemotherapy should be interpreted according to individual high-dose methotrexate scheduling.

ESHAP is an active regimen for relapsing Hodgkin's disease

BACKGROUND

Refractory or relapsing Hodgkin's disease is associated with a poor prognosis. There is no widely accepted salvage chemotherapy regimen for these patients. However, the addition of high-dose chemotherapy followed by autologous hematopoietic transplantation (AHT) has proven of benefit to them. A prospective clinical trial was carried out to evaluate the efficacy and toxicity of ESHAP (etoposide, methylprednisolone, high-dose cytarabine, and cisplatin).

PATIENTS AND METHODS

Twenty-two patients with refractory (5) or relapsing Hodgkin's disease (17) were entered and scheduled to receive three courses of ESHAP. Patients suitable for AHT were then given high-dose chemotherapy with CBV (cyclophosphamide, carmustine, and etoposide) plus AHT, whereas responding, non-AHT-suitable patients completed six ESHAP courses.

RESULTS

Nine patients achieved complete responses and seven partial responses (overall response rate 73%) with ESHAP. Grade 3-4 myelotoxicity was seen in 13 patients (59%). Nine patients received CBV plus AHT. At a median follow-up time of 50 months (range 6-96), seven patients (32%) are alive and disease-free. Three patients died of toxic effects of ESHAP (1) or CBV (2). Actuarial overall survival and disease-free survival were 35% and 27% at three years.

CONCLUSIONS

ESHAP is an active regimen for relapsing Hodgkin's disease, with myelosuppression as its dose-limiting toxicity. An increased risk of treatment-related mortality when it is combined with high-dose chemotherapy can not be ruled out.

Isoterracinolides A and B, novel bishomoditerpene lactones from euphorbia terracina

An extract of Euphorbia terracina L. has yielded six acylated polyhydroxy terpenoid lactones (1-6), which all display the C22 17-ethyljatrophane carbon framework. Four of these (1-4) are delta lactones belonging to the previously described terracinolide type, and two of them (2, 3) are new. Two further new compounds have been named isoterracinolides A (5) and B (6) and exhibit an eight-membered lactone ring. Another isolated new compound is the jolkinolide-type, ent-abietane gamma lactone (7).

Comparative analysis of the vascular actions of diterpenes isolated from Euphorbia canariensis

We have analysed the effects of 2,3-diepiingol 7,12-diacetate-8-isobutyrate (compound 1), ingenol-3-angelate-17-benzoate (compound 2), ingenol-3-angelate-17-benzoate-20-acetate (compound 3) and 3,5,7,8,9,15-hexahydroxyjatropha-6(17),11-dien-14-one-5,8-bi s(2-methylbutyrate)-7-(2-methylpropionate) (compound 4), four diterpenes isolated from E. canariensis, on the isometric tension developed by isolated rabbit basilar and carotid arteries. Concentration-response curves to these compounds were obtained cumulatively in both arteries at resting tension and active tone (KCl, 50 mM). At resting tension a concentration-dependent contraction was induced by the four compounds. In the basilar artery the order of potency was 3=1>2=4, without significant differences between Emax values. In the carotid artery the order of potency was 3>2=1=4 and there were no significant differences between the Emax (maximum effect) values of compounds 1-3, all of which were higher than that of compound 4. In pre-contracted basilar artery compounds 1-3 induced concentration-dependent relaxation and compound 4 was almost ineffective; the order of potency was 3>2=1 without significant differences between Emax values. In the carotid artery with active tone the four compounds tested induced further contractions; the order of potency was 3>2=4>1 without significant differences between Emax values. These results show that the four diterpenes are potent active substances in rabbit basilar and carotid arteries and that there are regional differences between their action. The four compounds tested contract basilar and carotid arteries at resting tension. Compounds 1-3 relax pre-contracted basilar artery but not carotid artery.

Analysis of rabbit vascular responses to DBI, an ingol derivative isolated from Euphorbia canariensis

We have analysed the effects of 7,12-O-diacetyl-8-O-benzoil-2,3-diepiingol (DBI), an ingol derivative isolated from E. canariensis, on isometric tension developed by isolated rabbit basilar and carotid arteries. Concentration-response curves to DBI (10(-8) - 3 x 10(-5) M) were obtained cumulatively in both arteries at resting tension and active tone (KCI, 50 mM). At resting tension, DBI induced a concentration-dependent contraction, which was not inhibited in Ca(2+)-free medium. H7 (1-(5-isoquinoline sulphonyl)-2-methylpiperazine dichloride) (10(-4) M) inhibited the DBI-induced contraction both in basilar and in carotid arteries. Calmidazolium (10(-4) M) inhibited the maximum contraction of the carotid artery to DBI, and completely abolished the response in the basilar artery. In pre-contracted basilar arteries DBI induced a concentration-dependent relaxation that was not modified by incubation with NG-nitro-L-arginine (L-NOARG; 10(-5) M) or indomethacin (10(-5) M). In the carotid artery with active tone DBI induced further contractions, which were not significantly modified by L-NOARG (10(-5) M) and were potentiated by indomethacin (10(-5) M). These results suggest that DBI contracts rabbit basilar and carotid arteries by a mechanism that is independent of extracellular Ca2+ and involves the participation both of protein kinase C and of calmodulin. DBI relaxes basilar but not carotid arteries by a mechanism independent of the liberation of nitric oxide and prostacyclin. In the carotid artery prostacyclin but not nitric oxide partially counteracts the contractile action of DBI.