Interventions in ADHD: A comparative review of stimulant medications and behavioral therapies

ADHD has a prevalence of approximately 10% in children with evidence supporting it's continuance into adulthood. This has a significant impact on how we address treatment at substance abuse facilities and also has implications for personal and occupational functioning. A lack of evidence to support the superiority of any one intervention over the other has created difficulties for both clinicians and parents. A recent review highlights long-term and short-term outcomes (Craig et al., 2015). This article reviews the benefits and pitfalls of both pharmacological interventions and behavioral therapies in the treatment of ADHD. Key articles were reviewed on the benefits and side effects of stimulants, the methods and benefits of behavioral interventions, and the effects of combination therapy. Google Scholar, PsychINFO, Medline, Cochrane, and CINAHL were searched with the following search words: Attention Deficit Hyperactivity Disorder, ADHD, Stimulant Medication, Behavioral Interventions, Combination Therapy, Cognitive Therapy, Functioning and Growth. It was found that stimulants are very effective during the period in which they are taken. While short term benefits are clear, longer term ones are not. Behavioral interventions play a key role for long-term improvement of executive functioning and organizational skills. There is a paucity of long-term randomized placebo controlled studies and current literature is inconclusive on what is the preferred intervention.

Molecular mechanisms in H2O2-induced increase in AT1 receptor gene expression in cardiac fibroblasts: A role for endogenously generated Angiotensin II

The AT1 receptor (AT1R) mediates the manifold actions of angiotensin II in the cardiovascular system. This study probed the molecular mechanisms that link altered redox status to AT1R expression in cardiac fibroblasts. Real-time PCR and western blot analysis showed that H2O2 enhances AT1R mRNA and protein expression via NADPH oxidase-dependent reactive oxygen species induction. Activation of NF-κB and AP-1, demonstrated by electrophoretic mobility shift assay, abolition of AT1R expression by their inhibitors, Bay-11-7085 and SR11302, respectively, and luciferase and chromatin immunoprecipitation assays confirmed transcriptional control of AT1R by NF-κB and AP-1 in H2O2-treated cells. Further, inhibition of ERK1/2, p38 MAPK and c-Jun N-terminal kinase (JNK) using chemical inhibitors or by RNA interference attenuated AT1R expression. Inhibition of the MAPKs showed that while ERK1/2 and p38 MAPK suffice for NF-κB activation, all three kinases are required for AP-1 activation. H2O2 also increased collagen type I mRNA and protein expression. Interestingly, the AT1R antagonist, candesartan, attenuated H2O2-stimulated AT1R and collagen mRNA and protein expression, suggesting that H2O2 up-regulates AT1R and collagen expression via local Angiotensin II generation, which was confirmed by real-time PCR and ELISA. To conclude, oxidative stress enhances AT1R gene expression in cardiac fibroblasts by a complex mechanism involving the redox-sensitive transcription factors NF-κB and AP-1 that are activated by the co-ordinated action of ERK1/2, p38 MAPK and JNK. Importantly, by causally linking oxidative stress to Angiotensin II and AT1R up-regulation in cardiac fibroblasts, this study offers a novel perspective on the pathogenesis of cardiovascular diseases associated with oxidative stress.

Molecular basis and functional significance of Angiotensin II-induced increase in Discoidin Domain Receptor 2 gene expression in cardiac fibroblasts

Delineation of mechanisms underlying the regulation of fibrosis-related genes in the heart is an important clinical goal as cardiac fibrosis is a major cause of myocardial dysfunction. This study probed the regulation of Discoidin Domain Receptor 2 (DDR2) gene expression and the regulatory links between Angiotensin II, DDR2 and collagen in Angiotensin II-stimulated cardiac fibroblasts. Real-time PCR and western blot analyses showed that Angiotensin II enhances DDR2 mRNA and protein expression in rat cardiac fibroblasts via NADPH oxidase-dependent reactive oxygen species induction. NF-κB activation, demonstrated by gel shift assay, abolition of DDR2 expression upon NF-κB inhibition, and luciferase and chromatin immunoprecipitation assays confirmed transcriptional control of DDR2 by NF-κB in Angiotensin II-treated cells. Inhibitors of Phospholipase C and Protein kinase C prevented Angiotensin II-dependent p38 MAPK phosphorylation that in turn blocked NF-κB activation. Angiotensin II also enhanced collagen gene expression. Importantly, the stimulatory effects of Angiotensin II on DDR2 and collagen were inter-dependent as siRNA-mediated silencing of one abolished the other. Angiotensin II promoted ERK1/2 phosphorylation whose inhibition attenuated Angiotensin II-stimulation of collagen but not DDR2. Furthermore, DDR2 knockdown prevented Angiotensin II-induced ERK1/2 phosphorylation, indicating that DDR2-dependent ERK1/2 activation enhances collagen expression in cells exposed to Angiotensin II. DDR2 knockdown was also associated with compromised wound healing response to Angiotensin II. To conclude, Angiotensin II promotes NF-κB activation that up-regulates DDR2 transcription. A reciprocal regulatory relationship between DDR2 and collagen, involving cross-talk between the GPCR and RTK pathways, is central to Angiotensin II-induced increase in collagen expression in cardiac fibroblasts.

Tuberculous celiac axis lymphadenopathy mimicking cystic pancreatic neoplasm - a diagnostic dilemma

Cystic pancreatic neoplasms are tumors with malignant potential treated surgically. Isolated tuberculosis of celiac lymph nodes is rare, treatment of this entity being non-surgical. Radiological appearances of cystic pancreatic neoplasm and tuberculous peripancreatic lymph nodal mass is similar and difficult to differentiate. Here we present a case of mass lesion in the region of pancreatic head mimicking cystic pancreatic neoplasm which was actually abdominal tuberculous lymphadenopathy proven by biopsy.

Mechanisms in cardiac fibroblast growth: an obligate role for Skp2 and FOXO3a in ERK1/2 MAPK-dependent regulation of p27kip1

Cardiac fibroblast hyperplasia associated with enhanced matrix deposition is a major determinant of tissue remodeling in several disease states of the heart. However, mechanisms controlling cell cycle progression in cardiac fibroblasts remain unexplored. Identification of cell cycle regulatory elements in these cells is important to develop strategies to check adverse cardiac remodeling under pathological conditions. This study sought to probe the mechanisms underlying ERK1/2-mediated p27Kip1 regulation in mitogenically stimulated cardiac fibroblasts. Addition of 10% fetal calf serum to quiescent cultures of adult rat cardiac fibroblasts promoted ERK1/2 activation, as evidenced by its phosphorylation status. Reduction in [3H]thymidine incorporation into DNA increased population doubling time, flow cytometry, and Western blot analysis showing reduced levels of cyclins D and A, p27Kip1 induction, and retinoblastoma protein (Rb) hypophosphorylation in ERK1/2-inhibited cells indicated ERK1/2 dependence of G1-S transition in cardiac fibroblasts. Lack of p27Kip1 protein in serum-stimulated, ERK1/2-active cells was associated with increased levels of Skp2, an E3 ubiquitin ligase for p27Kip1, whose knockdown by RNA interference induced p27Kip1 expression. Further, forced expression of Skp2 in ERK1/2-inhibited cells downregulated p27Kip1. Transcriptional upregulation of p27Kip1 mRNA in ERK1/2-inhibited cells, demonstrated by real-time PCR, correlated with forkhead box O 3a (FOXO3a) transcription factor activation, shown by gel shift assay. FOXO3a knockdown attenuated p27Kip1 mRNA and protein expression in ERK1/2-inhibited cells. We provide evidence for the first time that, in cardiac fibroblasts, activated ERK1/2 regulates p27Kip1 expression transcriptionally and posttranslationally via FOXO3a- and Skp2-dependent mechanisms. Additionally, this study uncovers interesting interactions between critical cell cycle regulatory elements that are only beginning to be understood.

cIAP-2 protects cardiac fibroblasts from oxidative damage: an obligate regulatory role for ERK1/2 MAPK and NF-κB

Cardiac fibroblasts are resistant to several pro-apoptotic factors that prevail in the diseased myocardium. Resistance to death signals may, in the short-term, enable these cells to play a central role in tissue repair following myocyte loss but, in the long-term, facilitate their persistence in the infarct scar, resulting in disproportionate stromal growth and pump dysfunction. Surprisingly, the molecular basis of apoptosis resistance in cardiac fibroblasts remains unclear. We explored the recruitment of anti-apoptotic mechanisms in cardiac fibroblasts subjected to oxidative stress, a major component of ischemia-reperfusion injury and heart failure. Cardiac fibroblasts exposed to H2O2 expressed enhanced levels of anti-apoptotic cIAP-2 mRNA and protein, revealed by real time PCR and western blot analysis, respectively. Pulmonary fibroblasts did not express cIAP-2 and were more susceptible than cardiac fibroblasts to H2O2. cIAP-2 knockdown by RNA interference promoted apoptosis in H2O2-treated cardiac fibroblasts. Electrophoretic mobility shift assay showed NF-κB activation in cells under oxidative stress. NF-κB inhibition in H2O2-treated cells resulted in significant attenuation of cIAP-2 mRNA and protein expression and apoptosis, indicating involvement of NF-κB in cell survival via regulation of cIAP-2. Further, pCMV promoter-driven constitutive expression of cIAP-2 reduced viability loss in NF-κB-inhibited cardiac fibroblasts exposed to oxidative stress. H2O2 also caused ERK1/2 activation, which, upon inhibition, prevented IκBα degradation and nuclear translocation of NF-κB. Moreover, ERK1/2 inhibition attenuated H2O2-induced cIAP-2 expression and compromised viability in H2O2-treated cardiac fibroblasts. We propose for the first time that ERK1/2-dependent activation of NF-κB and consequent induction of cIAP-2 protects cardiac fibroblasts from oxidative damage.

NF-κB inhibition compromises cardiac fibroblast viability under hypoxia

Cardiac fibroblasts are reported to be relatively resistant to stress stimuli compared to cardiac myocytes and fibroblasts of non-cardiac origin. However, the mechanisms that facilitate their survival under conditions of stress remain unclear. We explored the possibility that NF-κB protects cardiac fibroblasts from hypoxia-induced cell death. Further, we examined the expression of the antiapoptotic cIAP-2 and Bcl-2 in hypoxic cardiac fibroblasts, and their possible regulation by NF-κB. Phase contrast microscopy and propidium iodide staining revealed that cardiac fibroblasts are more resistant than pulmonary fibroblasts to hypoxia. Electrophoretic Mobility Shift Assay showed that hypoxia activates NF-κB in cardiac fibroblasts. Supershift assay indicated that the active NF-κB complex is a p65/p50 heterodimer. An I-κB-super-repressor was constructed that prevented NF-κB activation and compromised cell viability under hypoxic but not normoxic conditions. Similar results were obtained with Bay 11-7085, an inhibitor of NF-κB. Western blot analysis showed constitutive levels of Bcl-2 and hypoxic induction of cIAP-2 in these cells. NF-κB inhibition reduced cIAP-2 but not Bcl-2 levels in hypoxic cardiac fibroblasts. The results show for the first time that NF-κB is an important effector of survival in cardiac fibroblasts under hypoxic stress and that regulation of cIAP-2 expression may contribute to its pro-survival role.

p38 MAPK regulates G1-S transition in hypoxic cardiac fibroblasts

Cardiac fibroblast hyperplasia associated with augmented matrix production is central to wound healing following myocardial injury. Regulation of the cardiac fibroblast cell cycle by factors in the diseased myocardium that can potentially modify the hyperplastic response of cardiac fibroblasts has, however, not been investigated. We examined the regulation of the cardiac fibroblast cell cycle by hypoxia, a major constituent of myocardial ischemia. Significant reductions in DNA synthesis and cell number, and flow cytometry indicated decreased G1/S progression in hypoxic adult rat cardiac fibroblasts. Western blot analysis showed reduced levels of cyclin D and cyclin A, induction of p27 and hypophosphorylation of Rb under hypoxia. Skp2, which targets p27 for degradation, was significantly lower and inversely related to p27 protein levels in hypoxic cells. Marked p38 MAPK activation was observed under hypoxia and its inhibition using SB203580 reversed the effects of hypoxia on DNA synthesis, cell cycle phase distribution, p27, and cyclin D1 but not cyclin A. Interestingly, a 2-fold increase in p27 mRNA in hypoxic cells, demonstrated by real-time PCR, was unaffected by SB203580, which, however, reversed the hypoxic inhibition of Skp2. In summary, p38 MAPK is an important determinant of hypoxia-induced G0/G1 block in cardiac fibroblasts. p27 induction in hypoxic cardiac fibroblasts may involve direct transcriptional regulation, independent of p38 MAPK, and post-translational regulation via p38 MAPK-dependent suppression of its degradation by Skp2. The study identifies Skp2 as a potential downstream target of p38 MAPK, suggesting a novel mechanism of G1-S regulation in cardiac fibroblasts exposed to stress conditions.

Study of DSM-IV Axis I psychiatric disorders in patients with refractory complex partial seizures using a short structured clinical interview

Psychiatric disorders are a source of significant comorbidity in patients with refractory epilepsy, yet are often underrecognized. We assessed the prevalence of DSM-IV Axis I psychiatric disorders using a short structured clinical interview (Mini-International Psychiatric Interview [MINI]) in patients with medically refractory complex partial seizures. Consecutive patients with refractory epilepsy being evaluated with video/EEG monitoring and imaging for seizure focus localization and lateralization underwent MINI evaluation to assess for the presence of psychiatric disorders. Among 117 patients (74 male, 43 female) studied, 57 (48.7%) had at least one psychiatric disorder; 19 (16.2%) had depression, 10 (8.5%) dysthymia, 27 (23.0%) anxiety disorder, and 11(9.4%) other disorders. Most clinical features and epilepsy-related variables had no significant association with psychiatric disorder on logistic regression analysis. Almost half of the patients with refractory focal seizures have a coexistent psychiatric disorder, and its presence or absence cannot be predicted by their clinical profiles. All patients should be assessed and treated for psychiatric comorbidity to improve overall quality of life.

Unicystic ameloblastoma of the mandible--an unusual case report and review of literature

Ameloblastoma is a true neoplasm of odontogenic epithelial origin. It is the second most common odontogenic neoplasm, and only odontoma outnumbers it in reported frequency of occurrence. Its incidence, combined with its clinical behavior, makes ameloblastoma the most significant odontogenic neoplasm. Unicystic ameloblastoma (UA) refers to those cystic lesions that show clinical, radiographic, or gross features of a mandibular cyst, but on histologic examination show a typical ameloblastomatous epithelium lining part of the cyst cavity, with or without luminal and/or mural tumor growth. It accounts for 5-15% of all intraosseous ameloblastomas. We report a case of unicystic ameloblastoma in a 30-year-old female, and review the literature.

Breast cancer presenting as parotid tumour - first reported case in literature

Breast cancer presenting as parotid tumour is very rare. This is the first reported case in which parotid tumour was the presenting complaint of the patient. Since the patient was estrogen and progesterone receptor positive - was put on hormone therapy and responded well.

Paracrine effects of hypoxic fibroblast-derived factors on the MPT-ROS threshold and viability of adult rat cardiac myocytes

Cardiac fibroblasts contribute to multiple aspects of myocardial function and pathophysiology. The pathogenetic relevance of cytokine production by these cells under hypoxia, however, remains unexplored. With the use of an in vitro cell culture model, this study evaluated cytokine production by hypoxic cardiac fibroblasts and examined two distinct effects of hypoxic fibroblast-conditioned medium (HFCM) on cardiac myocytes and fibroblasts. Hypoxia caused a marked increase in the production of tumor necrosis factor (TNF)-alpha by cardiac fibroblasts. HFCM significantly enhanced the susceptibility of cardiac myocytes to reactive oxygen species (ROS)-induced mitochondrial permeability transition (MPT), determined by high-precision confocal line-scan imaging following controlled, photoexcitation-induced ROS production within individual mitochondria. Furthermore, exposure of cardiac myocytes to HFCM for 5 h led to loss of viability, as evidenced by change in morphology and annexin staining. HFCM also decreased DNA synthesis in cardiac fibroblasts. Normoxic fibroblast-conditioned medium spiked with TNF-alpha at 200 pg/ml, a concentration comparable to that in HFCM, promoted loss of myocyte viability and decreased DNA synthesis in cardiac fibroblasts. These effects of HFCM are similar to the reported effects of hypoxia per se on these cell types, showing that hypoxic fibroblast-derived factors may amplify the distinct effects of hypoxia on cardiac cells. Importantly, because both hypoxia and oxidant stress prevail in a setting of ischemia and reperfusion, the effects of soluble factors from hypoxic fibroblasts on the MPT-ROS threshold and viability of myocytes may represent a novel paracrine mechanism that could exacerbate ischemia-reperfusion injury to cardiomyocytes.

The adaptation to salinity: protein synthesis and some aspects of energy transduction in fish gill mitochondria

Exposure of freshwater fish to saline conditions brings about somewhat drastic changes in the mitochondrial energy metabolism. These include abolition of oxidative phosphorylation, ATP-induced contraction of swollen mitochondria and transhydrogenase activity. On the other hand the endogenous calcium levels and protein synthetic capacity are elevated. In vitro protein synthesis by mitochondria from freshwater and stressed fish shows qualitative and quantitative variations. Effluxing the excess calcium by treatment with NaCl or inhibiting the protein synthesis by chloramphenicol in stressed mitochondria restores almost all the functions. It is proposed that the energy potential formed by the mitochondrial membrane is channelized to perform different functions and that the ratio of channelization can be altered to suit the needs of the cell.

Substance P enhances soluble ICAM-1 release from adult rat cardiac fibroblasts by a p42/44 MAPK- and PKC-mediated mechanism

Substance P, a pro-inflammatory neuropeptide, is released from cardiac peptidergic nerves under conditions like ischemia but whether it modulates inflammatory processes in the heart remains unexplored. This study demonstrates for the first time that substance P augments the production of the soluble form of intercellular adhesion molecule-1, sICAM-1, by adult rat cardiac fibroblasts. However, RT-PCR showed no concomitant increase in ICAM-1 transcript levels, suggesting that the increase in sICAM-1 may involve post-transcriptional/translational mechanisms. Use of pharmacological inhibitors revealed that the stimulatory effect of substance P on sICAM-1 production is mediated by p42/44 MAPK and protein kinase C. Preliminary experiments also showed that the neuropeptide stimulates the production of prostaglandin E(2) by cardiac fibroblasts. The findings support the postulation that substance P may modulate multiple inflammatory responses within the myocardium through release of pro-inflammatory mediators from resident fibroblasts.

Hypoxia and antioxidants enhance soluble ICAM-1 release from cardiac fibroblasts

Intercellular adhesion molecule-1 plays a key role in mediating inflammatory and immune responses. There is also increasing appreciation of the role of its soluble form, sICAM-1, in regulating inflammation. This study evaluated the effects of hypoxia and N-acetyl-L-cysteine on sICAM-1 production by adult rat cardiac fibroblasts. By ELISA, hypoxia was found to cause a 61% increase in sICAM-1 in cardiac fibroblast culture supernates. However, RT-PCR did not reveal a concomitant increase in cell surface ICAM-1 transcript levels, suggesting that the increase in sICAM-1 may involve post-transcriptional and/or post-translational mechanisms. Using pharmacological inhibitors, it was observed that p42/44 MAPK and PKC mediate the stimulatory effect of hypoxia on sICAM-1 production. Remarkably, N-acetyl-L-cysteine caused a 3-fold increase in sICAM-1 by p42/44 MAPK-, p38 MAPK- and PKC-independent mechanisms. Pyrrolidine dithiocarbamate, another potent antioxidant, also augmented sICAM-1. The findings presented in this communication underscore the link between redox status and sICAM-1 release from cardiac fibroblasts. Further, because hypoxia is a major component of myocardial ischemia and is pro-inflammatory, and both N-acetylcysteine and pyrrolidine dithiocarbamate are clinically used antioxidants, the observations may have clinical significance.

Human protein reference database--2006 update

Human Protein Reference Database (HPRD) (http://www.hprd.org) was developed to serve as a comprehensive collection of protein features, post-translational modifications (PTMs) and protein-protein interactions. Since the original report, this database has increased to >20 000 proteins entries and has become the largest database for literature-derived protein-protein interactions (>30 000) and PTMs (>8000) for human proteins. We have also introduced several new features in HPRD including: (i) protein isoforms, (ii) enhanced search options, (iii) linking of pathway annotations and (iv) integration of a novel browser, GenProt Viewer (http://www.genprot.org), developed by us that allows integration of genomic and proteomic information. With the continued support and active participation by the biomedical community, we expect HPRD to become a unique source of curated information for the human proteome and spur biomedical discoveries based on integration of genomic, transcriptomic and proteomic data.

Cardiac fibrogenesis in magnesium deficiency: a role for circulating angiotensin II and aldosterone

Mechanisms underlying cardiac fibrogenesis in magnesium deficiency are unclear. It was reported earlier from this laboratory that serum from magnesium-deficient rats has a more pronounced stimulatory effect on cell proliferation, net collagen production, and superoxide generation in adult rat cardiac fibroblasts than serum from rats on the control diet. The profibrotic serum factors were, however, not identified. This study tested the hypothesis that circulating angiotensin II may modulate cardiac fibroblast activity in hypomagnesemic rats. Male Sprague-Dawley rats were pair-fed a magnesium-deficient (0.0008% Mg) or -sufficient (0.05%) diet for 6 days, and the effects of serum from these rats on [3H]thymidine and [3H]proline incorporation into cardiac fibroblasts from young adult rats were evaluated in the presence of losartan, an angiotensin II type 1 (AT1) receptor antagonist, and spironolactone, an aldosterone antagonist. Losartan and spironolactone markedly attenuated the stimulatory effects in vitro of serum from the magnesium-deficient and control groups, but the inhibitory effects were considerably higher in cells exposed to serum from magnesium-deficient animals. Circulating and cardiac tissue levels of angiotensin II were significantly elevated in magnesium-deficient animals (67.6% and 93.1%, respectively, vs. control). Plasma renin activity was 61.9% higher in magnesium-deficient rats, but serum angiotensin-converting enzyme activity was comparable in the two groups. Furthermore, preliminary experiments in vivo using enalapril supported a role for angiotensin II in magnesium deficiency. There was no significant difference between the groups in serum aldosterone levels. The findings suggest that circulating angiotensin II and aldosterone may stimulate fibroblast activity and contribute to a fibrogenic response in the heart in magnesium deficiency.

Differential response of cardiac fibroblasts from young adult and senescent rats to ANG II

The intracardiac ANG II-forming pathway is activated in the senescent myocardium, raising the possibility of enhanced ANG II effects on cardiac fibroblasts. This study established an in vitro model of cultured cardiac fibroblasts from aged rats to examine if the response of these cells to ANG II is modified in the aged heart. Levels of mRNA encoding renin, angiotensinogen, and the AT(1) receptor subtype in cardiac fibroblasts from young adult and senescent rats were quantified by RT-PCR, net collagen production by a hydroxyproline-based assay, and transforming growth factor (TGF)-beta levels using a commercial kit. In cardiac fibroblasts from young adult rats, ANG II significantly enhanced AT(1) mRNA levels, net collagen production, and TGF-beta production. In fibroblasts from the aged myocardium, ANG II downregulated AT(1) mRNA expression, had a less pronounced effect on net collagen production, and had no effect on TGF-beta production. Such age-related modification of the response of cardiac fibroblasts to ANG II may counteract the effects of augmented intracardiac ANG II production in the senescent heart, limiting fibrogenesis.

Pro-fibrogenic effects of magnesium deficiency in the cardiovascular system

Magnesium deficiency is known to produce cardiovascular injury. A large body of experimental evidence supports the postulation that an immuno-inflammatory reaction and increased oxidative stress may damage the myocardium and vasculature in magnesium deficiency. Reparative/reactive fibrosis in response to the injury has, however, received little attention. Recent evidence from a rodent model of acute magnesium deficiency suggests that humoral factors may activate cardiac fibroblasts by a free radical-mediated mechanism and contribute to cardiac fibrogenesis. A similar mechanism may also promote cellular hyperplasia and increased matrix synthesis in the vasculature.

Calcium- and superoxide anion-mediated mitogenic action of substance P on cardiac fibroblasts

Substance P is released from nerve endings in the heart under pathological conditions like ischemia, but its action on cardiac cells has not been investigated. This study tested the hypothesis that substance P is mitogenic to adult cardiac fibroblasts and delineated the underlying mechanism(s). Substance P, acting via neurokinin-1 (NK-1) receptors, stimulated cellular hyperplasia over a range of 1-10 micromol/l. It elicited no change in net collagen production, total protein synthesis, or cell protein content but increased (45)Ca uptake and superoxide generation. EGTA, N-acetyl-cysteine, and superoxide dismutase attenuated the hyperplastic response to substance P. A combination of substance P and EGTA enhanced superoxide generation without an increase in DNA synthesis, showing that an increase in superoxide production does not result in hyperplasia when extracellular Ca(2+) is chelated. Together, the data suggest that substance P may activate, via NK-1 receptors, a hyperplastic but not hypertrophic response in adult cardiac fibroblasts and that alterations in redox state and Ca(2+) homeostasis may act in concert to mediate its mitogenic action.

Superoxide-mediated activation of cardiac fibroblasts by serum factors in hypomagnesemia

Magnesium deficiency is known to produce myocardial fibrosis in different animal models, but the underlying mechanisms are unclear. However, circulating levels of pro-oxidant and mitogenic factors are reported to be elevated in a rodent model of acute magnesium deficiency, suggesting a role for humoral factors in the pathogenesis of the cardiovascular lesions. Probing the mechanism of cardiac fibrogenesis in magnesium deficiency, the present study furnished evidence that serum from magnesium-deficient rats has a more marked effect than serum from magnesium-sufficient rats on mitogenesis, net collagen production, and superoxide generation in cardiac fibroblasts from young adult rats. The enhanced mitogenic response was abolished by superoxide dismutase and N-acetyl cysteine, showing that it is mediated by superoxide anion. Further, a modest inhibitory effect of the neurokinin-1 receptor antagonist, spantide, suggested that factors acting via neurokinin-1 receptors may partly modulate cardiac fibroblast function in magnesium deficiency. The findings are consistent with the postulation that serum factors may activate cardiac fibroblasts via a superoxide-mediated mechanism and contribute to the fibrogenic response in the heart in magnesium deficiency.

L-type calcium channel blockers and EGTA enhance superoxide production in cardiac fibroblasts

Since the recognition of the importance of calcium ions to cardiac contractility, the effects of alterations in calcium homeostasis on cardiac myocyte function have attracted immense attention. However, the possibility that changes in extracellular calcium concentration or the administration of calcium channel blockers may exert significant effects on cardiac fibroblasts has not hitherto been explored. This communication presents evidence, for the first time, that EGTA, calcium-free incubation and L-type calcium channel blockers increase endogenous superoxide production in adult rat cardiac fibroblasts. A combination of ryanodine and EGTA was found to have an even greater effect. The observations indicate that extracellular calcium levels influence endogenous superoxide production in cardiac fibroblasts and support the postulation that myocardial fibroblasts may contribute to the cardiac effects of calcium channel blockers and alterations in extracellular calcium concentration.

Model of cardiovascular injury in magnesium deficiency

Magnesium deficiency is known to produce cardiovascular lesions. It is, however, not clear as to what constitutes magnesium deficiency - reduced serum levels, reduced tissue levels or reduced intracellular levels of the ionic form of the element. This article cites evidence in support of a hypothesis that a fall in serum magnesium levels may trigger a temporal sequence of events involving vasoconstriction, hemodynamic alterations and vascular endothelial injury to produce pro-inflammatory, pro-oxidant and pro-fibrogenic effects, resulting in initial perivascular myocardial fibrosis which, in turn, would cause myocardial damage and replacement fibrosis. Further, angiotensin II may be the prime mover of the pathogenetic cascade in magnesium deficiency. Importantly, such a mechanism of cardiovascular injury would be independent of a reduction in myocardial or vascular tissue levels of magnesium.

Alterations in collagen metabolism and increased fibroproliferation in the heart in cerium-treated rats: implications for the pathogenesis of endomyocardial fibrosis

Cerium (Ce), a rare earth element, has been postulated to play a role in the pathogenesis of tropical endomyocardial fibrosis (EMF). Investigations carried out recently in pursuance of the postulation furnished histological evidence of EMF and increased cardiac collagen content in rats on prolonged administration of Ce. The present study was undertaken to understand the molecular basis of myocardial injury and fibrosis produced by the element. This article presents evidence of increased lipid peroxidation and elevated rates of fibroblast proliferation and collagen deposition in the heart in Ce-treated rats. It is suggested that the element may trigger a wound-healing response in the cardiac tissue leading to cardiac fibrosis.

Magnesium deficiency enhances oxidative stress and collagen synthesis in vivo in the aorta of rats

Magnesium deficiency has been shown to produce vascular lesions in experimental animals, but the underlying mechanisms of vascular injury are not clear. It has been reported that in rodents, magnesium deficiency enhances circulating levels of factors that promote free radical generation and are mitogenic. In pursuance of these observations, the present study tested the hypothesis that magnesium deficiency may enhance oxidative stress and trigger an accelerated growth response in vivo in the aorta of rats. Oxidative stress was evaluated in terms of levels of thiobarbituric acid-reactive substances in the serum and aorta and activity of superoxide dismutase and catalase in the aorta; fractional rates of collagen synthesis were assessed using [3H]-proline. Serum and tissue levels of magnesium and calcium were determined by atomic absorption spectrophotometry. The present study demonstrated for the first time that magnesium deficiency significantly (P < 0.001) increases levels of thiobarbituric acid-reactive substances in the aorta of rats. Other changes in the aorta of animals on the Mg-deficient diet included a significant reduction (54%, P < 0.001) in the activity of superoxide dismutase and catalase (37%, P < 0.01) and a 19% increase in net fractional rates of collagen synthesis (P < 0.05). While serum magnesium was significantly reduced in these animals (P < 0.001), aortic tissue levels of magnesium in these animals remained unaltered throughout the duration of the study, suggesting the existence of other control mechanisms, apart from reduced tissue levels of magnesium, mediating the observed effects. These findings suggest that magnesium deficiency may trigger a wound healing response, involving oxidative injury and growth stimulation, in the vascular system.

Depressed antioxidant defense in rat heart in experimental magnesium deficiency. Implications for the pathogenesis of myocardial lesions

Magnesium (Mg) deficiency has been shown to produce myocardial lesions in different experimental models. Based on several lines of evidence, it has been proposed that oxidative injury to the cardiac muscle may explain the pathobiology of such lesions. In pursuance of this postulation, the present study examined the effect of dietary deficiency of Mg on the activity of the antioxidant enzymes, superoxide dismutase (SOD) and catalase, in rat heart. This article reports a significant lowering of the activity of both these enzymes in the cardiac tissue in Mg-deficient rats. Since depressed antioxidant defense in the heart may enhance myocardial susceptibility to oxidative injury, the observation is of possible relevance to the pathogenesis of cardiac lesions in Mg deficiency.

Magnesium deficiency-related changes in lipid peroxidation and collagen metabolism in vivo in rat heart

Magnesium deficiency is known to produce a cardiomyopathy, characterised by myocardial necrosis and fibrosis. As part of the ongoing investigations in this laboratory to establish the biochemical correlates of these histological changes, the present study probed the extent of lipid peroxidation and alterations in collagen metabolism in the heart in rats fed a magnesium-deficient diet for 28, 60 or 80 days. While lipid peroxidation was measured by the thiobarbituric acid reaction, collagen turnover rates and fibroblast proliferation were assessed using [3H]-proline and [3H]-thymidine, respectively. Tissue levels of magnesium and calcium were determined by atomic absorption spectrophotometry. A 39% increase in the cardiac tissue level of thiobarbituric acid reactive substances was observed on day 60 of deficiency (p < 0.001). A marked drop in collagen deposition rate (59%, p < 0.001%) on day 28 but a significant rise in fractional synthesis rate (12%, p < 0.001) and collagen deposition rate (24%, p < 0.001) on day 60 were observed. A fibroproliferative response in the heart was evident on day 80 but not at earlier time-points. Thus, the present study provides evidence of increased lipid peroxidation and net deposition of collagen in the myocardium in response to dietary deficiency of magnesium. These changes were, however, not directly related to alterations in the tissue levels of Mg. It is suggested that the increase in cardiac collagen synthesis and fibroplasia associated with Mg deficiency may represent reparative fibrogenesis, upon oxidative damage to the cardiac muscle, and is mediated by a mechanism independent of changes in cardiac tissue levels of Mg.

Cerium stimulates protein biosynthesis in rat heart in vivo

The aim of the study was to ascertain whether Ce, a lanthanide that has been implicated in the pathogenesis of tropical endomyocardial fibrosis, interferes with the biosynthetic repertoire of the cardiac muscle in vivo. Female Sprague-Dawley rats received Ce chloride iv at 1.3 mg/kg body wt.; controls received an equal volume of physiological saline. Rates of protein synthesis and transcription in cardiac muscle, measured in terms of incorporation of (3H)-phenylalanine and (3H)-uridine, respectively, into trichloroacetic acid-insoluble material were found to be significantly higher in Ce-treated animals. As low levels of Ce were earlier shown to stimulate collagen as well as noncollagen protein synthesis in cardiac fibroblasts in vitro, the stimulatory effect of the element in vivo reported here supports the speculation that it may influence the expression of proteins like collagen in the heart and contribute to their accumulation as in endomyocardial fibrosis.

Paradoxical effect of cerium on collagen synthesis in cardiac fibroblasts

The present study examined the effect of cerium on collagen synthesis in cultured cardiac fibroblasts and explants. At 100 nM, a concentration comparable with that found in the cardiac tissue of patients with endomyocardial fibrosis, the element was found to enhance the incorporation of tritiated proline into collagen and non-collagen proteins while at 10 microM, it had an inhibitory effect. Cerium was found to have no effect on rates of DNA synthesis in fibroblasts at 100 nM. However, at this concentration, the element markedly enhanced the incorporation of tritiated uridine into RNA, suggesting that cerium may act at the level of transcription to stimulate collagen and non-collagen protein syntheses. The stimulatory action of very low levels of cerium on collagen synthesis may contribute to the accumulation of collagen seen in endomyocardial fibrosis.

Cerium depresses protein synthesis in cultured cardiac myocytes and lung fibroblasts

The present study examined the effect of Cerium on protein synthesis in cultured cardiac myocytes and lung fibroblasts exposed to normal and markedly subnormal levels of Mg2+. Cerium was found to have a general inhibitory effect on protein synthesis in these cell types, including the synthesis of myofibrillar proteins in the cardiac myocytes. Further, the effect of the metal ion was more pronounced in cells exposed to the Mg2(+)-deficient medium. The possible implications of the observations are discussed.

Interactions of thorium and cerium with adenine nucleotides

The present study demonstrates an effect of the actinide, Thorium (Th), and the lanthanide, Cerium (Ce), on the non-enzymatic hydrolysis of adenine and guanine nucleotides. Thorium was found to be a more effective catalyst of the reaction than Cerium. Further, both the elements promoted the binding of Creatine kinase (CK) to Cibacron blue F3 GA, the substrate analogue of the enzyme, even in the absence of Mg2+, the physiological cofactor. These observations imply that toxic heavy metals can mimic the functional effects of the essential elements despite differences in their physicochemical properties.

Synthetic hydrogel microspheres as substrata for cell adhesion and growth

Cross-linked poly(methyl methacrylate) (PMMA) microspheres were subjected to alkaline hydrolysis to obtain hydrophilic microspheres having carboxyl residues distributed throughout the matrix. These microspheres were found to support the growth of human skin fibroblasts and human heart and lung cells. Further, fibroblasts grown on them were found to be comparable with those grown on the commercial tissue culture plate with respect to [14C]amino acid uptake and incorporation into proteins. The hydrolyzed PMMA microspheres may find application as a microcarrier for cell culture.

Salinity adaptation in fish: interaction of thyroxine with fish gill mitochondria

When the freshwater fish Sarotherodon mossambicus is exposed to an ionoosmotic stress, extensive changes take place in the energetics of the gill mitochondria. These changes are reversed when thyroxine is administered to the fish prior to exposure to stress [K. Shivakumar and J. Jayaraman (1984) Arch. Biochem. Biophys. 233, 728]. The presence of a thyroxine binding component in the mitochondrial inner membrane, its characteristics, and its possible involvement in the salinity adaptation process are discussed.

Salinity adaptation in fish: effect of thyroxine on mitochondrial status

Upon transfer of the fresh-water fish, Sarotherodon mossambicus, to 50% sea water, extensive changes take place in the functions of the gill mitochondria. The changes are (i) loss of ADP/O and RCI; (ii) loss of the ability to contract upon addition of ATP-Mg2+; (iii) lowered energy-dependent 45Ca uptake; (iv) increased amino acid incorporation capacity; (v) increased adenine nucleotide content; and (vi) a higher endogenous Ca2+ content. Administration of thyroxine to the fish reversed these changes, and the effect of thyroxine was also not transient. It is suggested that thyroxine promotes mitochondriogenesis, thereby effecting a restoration of the stress-affected mitochondrial functions.