The mitochondrial ATP-dependent potassium channel (mitoKATP) controls skeletal muscle structure and function

MitoKATP is a channel of the inner mitochondrial membrane that controls mitochondrial K+ influx according to ATP availability. Recently, the genes encoding the pore-forming (MITOK) and the regulatory ATP-sensitive (MITOSUR) subunits of mitoKATP were identified, allowing the genetic manipulation of the channel. Here, we analyzed the role of mitoKATP in determining skeletal muscle structure and activity. Mitok-/- muscles were characterized by mitochondrial cristae remodeling and defective oxidative metabolism, with consequent impairment of exercise performance and altered response to damaging muscle contractions. On the other hand, constitutive mitochondrial K+ influx by MITOK overexpression in the skeletal muscle triggered overt mitochondrial dysfunction and energy default, increased protein polyubiquitination, aberrant autophagy flux, and induction of a stress response program. MITOK overexpressing muscles were therefore severely atrophic. Thus, the proper modulation of mitoKATP activity is required for the maintenance of skeletal muscle homeostasis and function.

Mitochondrial Cation Signalling in the Control of Inflammatory Processes

Mitochondria are the bioenergetic organelles responsible for the maintenance of cellular homeostasis and have also been found to be associated with inflammation. They are necessary to induce and maintain innate and adaptive immune cell responses, acting as signalling platforms and mediators in effector responses. These organelles are also known to play a pivotal role in cation homeostasis as well, which regulates the inflammatory responses through the modulation of these cation channels. In particular, this review focuses on mitochondrial Ca2+ and K+ fluxes in the regulation of inflammatory response. Nevertheless, this review aims to understand the interplay of these inflammation inducers and pathophysiological conditions. In detail, we discuss some examples of chronic inflammation such as lung, bowel, and metabolic inflammatory diseases caused by a persistent activation of the innate immune response due to a dysregulation of mitochondrial cation homeostasis.

Defective excitation-contraction coupling and mitochondrial respiration precede mitochondrial Ca2+ accumulation in spinobulbar muscular atrophy skeletal muscle

Polyglutamine expansion in the androgen receptor (AR) causes spinobulbar muscular atrophy (SBMA). Skeletal muscle is a primary site of toxicity; however, the current understanding of the early pathological processes that occur and how they unfold during disease progression remains limited. Using transgenic and knock-in mice and patient-derived muscle biopsies, we show that SBMA mice in the presymptomatic stage develop a respiratory defect matching defective expression of genes involved in excitation-contraction coupling (ECC), altered contraction dynamics, and increased fatigue. These processes are followed by stimulus-dependent accumulation of calcium into mitochondria and structural disorganization of the muscle triads. Deregulation of expression of ECC genes is concomitant with sexual maturity and androgen raise in the serum. Consistent with the androgen-dependent nature of these alterations, surgical castration and AR silencing alleviate the early and late pathological processes. These observations show that ECC deregulation and defective mitochondrial respiration are early but reversible events followed by altered muscle force, calcium dyshomeostasis, and dismantling of triad structure.

Myonecrosis Induction by Intramuscular Injection of CTX

Skeletal muscle, one of the most abundant tissue in the body, is a highly regenerative tissue. Indeed, compared to other tissues that are not able to regenerate after injury, skeletal muscle can fully regenerate upon mechanically, chemically, and infection-induced trauma. Several injury models have been developed to thoroughly investigate the physiological mechanisms regulating skeletal muscle regeneration. This protocol describes how to induce muscle regeneration by taking advantage of a cardiotoxin (CTX)-induced muscle injury model. The overall steps include CTX injection of tibialis anterior (TA) muscles of BL6N mice, collection of regenerating muscles at different time points after CTX injury, and histological characterization of regenerating muscles. Our protocol, compared with others such as those for freeze-induced injury models, avoids laceration or infections of the muscles since it involves neither surgery nor suture. In addition, our protocol is highly reproducible, since it causes homogenous myonecrosis of the whole muscle, and further reduces animal pain and stress. Graphical abstract.

Nerve-dependent distribution of subsynaptic type 1 inositol 1,4,5-trisphosphate receptor at the neuromuscular junction

Inositol 1,4,5-trisphosphate receptors (IP3Rs) are enriched at postsynaptic membrane compartments of the neuromuscular junction (NMJ), surrounding the subsynaptic nuclei and close to nicotinic acetylcholine receptors (nAChRs) of the motor endplate. At the endplate level, it has been proposed that nerve-dependent electrical activity might trigger IP3-associated, local Ca2+ signals not only involved in excitation-transcription (ET) coupling but also crucial to the development and stabilization of the NMJ itself. The present study was undertaken to examine whether denervation affects the subsynaptic IP3R distribution in skeletal muscles and which are the underlying mechanisms. Fluorescence microscopy, carried out on in vivo denervated muscles (following sciatectomy) and in vitro denervated skeletal muscle fibers from flexor digitorum brevis (FDB), indicates that denervation causes a reduction in the subsynaptic IP3R1-stained region, and such a decrease appears to be determined by the lack of muscle electrical activity, as judged by partial reversal upon field electrical stimulation of in vitro denervated skeletal muscle fibers.

CoQ10 and Resveratrol Effects to Ameliorate Aged-Related Mitochondrial Dysfunctions

Mitochondria participate in the maintenance of cellular homeostasis. Firstly, mitochondria regulate energy metabolism through oxidative phosphorylation. In addition, they are involved in cell fate decisions by activating the apoptotic intrinsic pathway. Finally, they work as intracellular signaling hubs as a result of their tight regulation of ion and metabolite concentrations and other critical signaling molecules such as ROS. Aging is a multifactorial process triggered by impairments in different cellular components. Among the various molecular pathways involved, mitochondria are key regulators of longevity. Indeed, mitochondrial deterioration is a critical signature of the aging process. In this scenario, we will focus specifically on the age-related decrease in CoQ levels, an essential component of the electron transport chain (ETC) and an antioxidant, and how CoQ supplementation could benefit the aging process. Generally, any treatment that improves and sustains mitochondrial functionality is a good candidate to counteract age-related mitochondrial dysfunctions. In recent years, heightened attention has been given to natural compounds that modulate mitochondrial function. One of the most famous is resveratrol due to its ability to increase mitochondrial biogenesis and work as an antioxidant agent. This review will discuss recent clinical trials and meta-analyses based on resveratrol and CoQ supplementation, focusing on how these compounds could improve mitochondrial functionality during aging.

The mitochondrial calcium homeostasis orchestra plays its symphony: Skeletal muscle is the guest of honor

Skeletal muscle mitochondria are placed in close proximity of the sarcoplasmic reticulum (SR), the main intracellular Ca²⁺ store. During muscle activity, excitation of sarcolemma and of T-tubule triggers the release of Ca²⁺ from the SR initiating myofiber contraction. The rise in cytosolic Ca²⁺ determines the opening of the mitochondrial calcium uniporter (MCU), the highly selective channel of the inner mitochondrial membrane (IMM), causing a robust increase in mitochondrial Ca²⁺ uptake. The Ca²⁺-dependent activation of TCA cycle enzymes increases the synthesis of ATP required for SERCA activity. Thus, Ca²⁺ is transported back into the SR and cytosolic [Ca²⁺] returns to resting levels eventually leading to muscle relaxation. In recent years, thanks to the molecular identification of MCU complex components, the role of mitochondrial Ca²⁺ uptake in the pathophysiology of skeletal muscle has been uncovered. In this chapter, we will introduce the reader to a general overview of mitochondrial Ca²⁺ accumulation. We will tackle the key molecular players and the cellular and pathophysiological consequences of mitochondrial Ca²⁺ dyshomeostasis. In the second part of the chapter, we will discuss novel findings on the physiological role of mitochondrial Ca²⁺ uptake in skeletal muscle. Finally, we will examine the involvement of mitochondrial Ca²⁺ signaling in muscle diseases.

Skeletal muscle mitochondria in health and disease

Mitochondrial activity warrants energy supply to oxidative myofibres to sustain endurance workload. The maintenance of mitochondrial homeostasis is ensured by the control of fission and fusion processes and by the mitophagic removal of aberrant organelles. Many diseases are due to or characterized by dysfunctional mitochondria, and altered mitochondrial dynamics or turnover trigger myopathy per se. In this review, we will tackle the role of mitochondrial dynamics, turnover and metabolism in skeletal muscle, both in health and disease.

The Mitochondrial Ca2+ Uptake and the Fine-Tuning of Aerobic Metabolism

Recently, the role of mitochondrial activity in high-energy demand organs and in the orchestration of whole-body metabolism has received renewed attention. In mitochondria, pyruvate oxidation, ensured by efficient mitochondrial pyruvate entry and matrix dehydrogenases activity, generates acetyl CoA that enters the TCA cycle. TCA cycle activity, in turn, provides reducing equivalents and electrons that feed the electron transport chain eventually producing ATP. Mitochondrial Ca²⁺ uptake plays an essential role in the control of aerobic metabolism. Mitochondrial Ca²⁺ accumulation stimulates aerobic metabolism by inducing the activity of three TCA cycle dehydrogenases. In detail, matrix Ca²⁺ indirectly modulates pyruvate dehydrogenase via pyruvate dehydrogenase phosphatase 1, and directly activates isocitrate and α-ketoglutarate dehydrogenases. Here, we will discuss the contribution of mitochondrial Ca²⁺ uptake to the metabolic homeostasis of organs involved in systemic metabolism, including liver, skeletal muscle, and adipose tissue. We will also tackle the role of mitochondrial Ca²⁺ uptake in the heart, a high-energy consuming organ whose function strictly depends on appropriate Ca²⁺ signaling.

Asylum seekers and inequalities in healthcare: a mixed-method research in Emilia-Romagna region

Background

In the past few years more than 30,000 asylum seekers arrived in Emilia-Romagna region. Guidelines were developed to screen the newly arrived, mainly focused on communicable diseases (CDs). However, asylum seekers who are out of the institutional reception system do not have access to such screenings. In order to assess the implementation and reach of these guidelines with respect to the target population, in 2019 a mixed-method survey was carried out.

Methods

A questionnaire with 35 closed and 11 open questions, based on a synthesis of the regional and national guidelines, was carried out with referents of the regional clinics that provide healthcare to asylum seekers. The collected questionnaires were processed through descriptive statistical analysis for the closed questions and text analysis for the open questions.

Results

Questionnaires were collected from 14 clinics. All clinics provide first visit and screening for CDs upon arrival, following the regional guidelines. However, enrolment in the national healthcare system was found to be delayed for periods of up to 6 months, resulting in discontinuity of care. Administrative and cultural barriers in accessing health and social services were repeatedly reported, the latter often linked to lack of cultural mediation services. Financial barriers were also reported, particularly with respect to dental care and pharmaceuticals. Results also show that asylum seekers within the institutional reception system can more easily overcome the reported barriers compared to those out of the system. Such inequality in accessing healthcare is reported also for the TB screening process.

Conclusions

Even if access to healthcare for asylum seekers is regulated by norms and guidelines, barriers are consistently reported. Moreover, asylum seekers within or outside the reception system face different barriers in accessing healthcare services. Such local evidence can be very relevant to inform actions that improve health equity.

Key messages

Even if access to healthcare for asylum seekers is regulated by law, barriers are consistently reported and impact disproportionately on those who are out of the institutional reception system. A mixed-method approach that generates local evidence on the barriers that asylum seekers face in accessing healthcare and on their causes is key to inform actions that improve health equity.

Health system response to large scale migration: the case of Emilia-Romagna region

Background

In Italy, recent changes in migration flows posed complex public health challenges. The Emilia-Romagna region (ERR) was one of the first regions to adopt specific policies addressing the health of newly arrived asylum seekers. In our study, we analysed the regional health system response comparing it to the regional and national guidelines, in order to assess its strengths and its critical areas.

Methods

In 2019, we conducted a survey among the referents of the regional clinics that provide healthcare to asylum seekers, in order to learn about local policies, challenges and best practices. A questionnaire with 35 closed and 11 open questions was administered and analysed through descriptive statistical analysis and text analysis.

Results

Regional policies showed good responsiveness and Local Health Authorities (LHAs) adhered to the guidelines. A special permit was introduced to grant asylum seekers access to healthcare, which also allowed integration of health data into the regional health information system. However, data integration was done in only 2 clinics out of 14. Instances of discretion in issuing the special permit were reported, due to ambiguity in the rules and inadequate training of office workers. Policies and LHAs protocols focused greatly on the arrival phase and on Communicable Diseases (CDs) surveillance. Other areas - such as protection of vulnerable groups, health promotion, NCDs - were prioritized in the national guidelines, but unevenly considered throughout the region, also due to lack of resources. Some clinics responded autonomously to these gaps with local resources.

Conclusions

The ERR health response to the influx of asylum seekers was rapid but incomplete. Interventions focused more on CDs surveillance than on responding to asylum seekers' health needs in terms of quality, access and equity. Areas to be strengthened include protection of vulnerable groups, health promotion and NCDs, together with coordination and long-term planning.

Key messages

The Emilia-Romagna region health response to the influx of asylum seekers reflects an emergency approach focused on communicable diseases, while NCDs and health promotion are relatively neglected. The health system in Emilia-Romagna needs to be strengthened in its capacity to respond to asylum seekers’ health needs. Health policies and practices should be planned to ensure equity and quality.

Chronic kidney disease in migrant and non-migrant populations: data from an Italian regional project

Background

The proportion of migrants among incident patients with chronic kidney disease (CKD) in the Emilia-Romagna region is steadily increasing. Inequalities in access to health services and in outcomes between non-migrant and migrant patients already known in the literature are found also for those affected by CKD. We compared migrants' groups and Italian patients to provide evidence which may be useful to public health professionals and nephrologists for migrant patients' management.

Methods

Italian and migrant patients followed up in PIRP (a regional project devised to delay progression to kidney failure in subjects with CKD) were identified. Migrants were grouped by geographical area of origin and compared to Italians by means of descriptive statistics and survival analysis.

Results

As of 30.4.2020, migrants account for 3.1% (n = 955/30523) of all PIRP patients and 4.2% (n = 481/11335) of prevalent patients; their proportion among incident patients grew from 1.0% in 2004 to 5.5% in 2019. All areas of origin were adequately represented, from 6.4% of East Asia to 26.1% of East Europe. Wide differences were found for: age at first visit (Italians=73.1 years vs. Sub-Saharians=47.7), proportion of males (75.0% for South Asians to 49.6% of East Europeans), diabetes (from 45.1% in East Asians to 19.4% in Sub-Saharians), comorbidities and type of nephropathy. Italians had the smallest median annual eGFR decrease (-1.0 ml/min), while the largest were found in migrants from East Asia (-2.2) and Arab States (-2.5). 5-year survival to renal death (dialysis or transplantation) was lower in South Asians (51.4%) than in Latino-Americans (85.3%) and Italians (85.0%).

Conclusions

Migrant chronic kidney disease patients have widely different features and outcomes compared to non-migrants and among migrant subgroups. Our findings pave the way to further investigation, whose results may be essential to tailor surveillance and treatment programs on specific groups of migrants.

Key messages

Among chronic kidney disease patients, non-migrants and migrants exhibit different clinical characteristics and outcomes, and thus require different surveillance and treatment approaches. Future research should analyze the causes of disparities between migrant and non-migrant chronic kidney disease patients, specifically focusing on those related to inequalities in access to healthcare.

Loss of mitochondrial calcium uniporter rewires skeletal muscle metabolism and substrate preference

Skeletal muscle mitochondria readily accumulate Ca²⁺ in response to SR store-releasing stimuli thanks to the activity of the mitochondrial calcium uniporter (MCU), the highly selective channel responsible for mitochondrial Ca²⁺ uptake. MCU positively regulates myofiber size in physiological conditions and counteracts pathological loss of muscle mass. Here we show that skeletal muscle-specific MCU deletion inhibits myofiber mitochondrial Ca²⁺ uptake, impairs muscle force and exercise performance, and determines a slow to fast switch in MHC expression. Mitochondrial Ca²⁺ uptake is required for effective glucose oxidation, as demonstrated by the fact that in muscle-specific MCU^-/- myofibers oxidative metabolism is impaired and glycolysis rate is increased. Although defective, mitochondrial activity is partially sustained by increased fatty acid (FA) oxidation. In MCU^-/- myofibers, PDP2 overexpression drastically reduces FA dependency, demonstrating that decreased PDH activity is the main trigger of the metabolic rewiring of MCU^-/- muscles. Accordingly, PDK4 overexpression in MCU^fl/fl myofibers is sufficient to increase FA-dependent respiration. Finally, as a result of the muscle-specific MCU deletion, a systemic catabolic response impinging on both liver and adipose tissue metabolism occurs.

Mitochondrial Calcium Increase Induced by RyR1 and IP3R Channel Activation After Membrane Depolarization Regulates Skeletal Muscle Metabolism

Aim: We hypothesize that both type-1 ryanodine receptor (RyR1) and IP₃-receptor (IP₃R) calcium channels are necessary for the mitochondrial Ca²⁺ increase caused by membrane depolarization induced by potassium (or by electrical stimulation) of single skeletal muscle fibers; this calcium increase would couple muscle fiber excitation to an increase in metabolic output from mitochondria (excitation-metabolism coupling).

Methods: Mitochondria matrix and cytoplasmic Ca²⁺ levels were evaluated in fibers isolated from flexor digitorium brevis muscle using plasmids for the expression of a mitochondrial Ca²⁺ sensor (CEPIA3mt) or a cytoplasmic Ca²⁺ sensor (RCaMP). The role of intracellular Ca²⁺ channels was evaluated using both specific pharmacological inhibitors (xestospongin B for IP₃R and Dantrolene for RyR1) and a genetic approach (shIP₃R1-RFP). O₂ consumption was detected using Seahorse Extracellular Flux Analyzer.

Results: In isolated muscle fibers cell membrane depolarization increased both cytoplasmic and mitochondrial Ca²⁺ levels. Mitochondrial Ca²⁺ uptake required functional inositol IP₃R and RyR1 channels. Inhibition of either channel decreased basal O₂ consumption rate but only RyR1 inhibition decreased ATP-linked O₂ consumption. Cell membrane depolarization-induced Ca²⁺ signals in sub-sarcolemmal mitochondria were accompanied by a reduction in mitochondrial membrane potential; Ca²⁺ signals propagated toward intermyofibrillar mitochondria, which displayed increased membrane potential. These results are compatible with slow, Ca²⁺-dependent propagation of mitochondrial membrane potential from the surface toward the center of the fiber.

Conclusion: Ca²⁺-dependent changes in mitochondrial membrane potential have different kinetics in the surface vs. the center of the fiber; these differences are likely to play a critical role in the control of mitochondrial metabolism, both at rest and after membrane depolarization as part of an “excitation-metabolism” coupling process in skeletal muscle fibers.

Localized morphea after breast implant for breast cancer: A case report

PURPOSE

Early breast cancer follow-up guidelines for patients who underwent surgery suggest a regular and accurate clinical examination of the breast area, for an early identification of cutaneous or subcutaneous breast cancer relapse. Nonetheless, breast skin lesions arising in patients treated with mastectomy for breast cancer can be caused by several diseases. A series of diagnostic hypotheses should be considered, not only focusing on cutaneous metastasis, but also on dermatologic and systemic diseases.

CASE REPORT

In February 2015, a 37-year-old patient underwent a right subcutaneous mastectomy for stage IIA breast cancer. Five months after beginning adjuvant chemotherapy, she noted hyperpigmentation and thickening of the skin on the right breast. Differential diagnosis included local relapse, skin infection, lymphoma, or primary cutaneous disease, and a skin biopsy was performed. The histopathologic specimen showed full-thickness sclerosis, with features of localized morphea. Therapy with clobetasol was prescribed, with progressive resolution of the thickness. The collaboration between many professionals in a multidisciplinary team (oncologist, dermatologist, plastic surgeon, and pathologist) was crucial to achieving the diagnosis.

CONCLUSION

In the literature, some articles describe correlation between connective tissue diseases and silicone breast implants, but the pathogenetic mechanisms are unknown. We report a rare case of breast morphea after positioning a silicone implant in a patient who had undergone mastectomy. This clinical report represents an interesting model of multidisciplinary management of a patient with breast cancer who developed an uncommon dermatologic disease. Further studies are needed to clarify the association between silicone implants and breast morphea.

Mitochondrial calcium uptake in organ physiology: from molecular mechanism to animal models

Mitochondrial Ca²⁺ is involved in heterogeneous functions, ranging from the control of metabolism and ATP production to the regulation of cell death. In addition, mitochondrial Ca²⁺ uptake contributes to cytosolic [Ca²⁺] shaping thus impinging on specific Ca²⁺-dependent events. Mitochondrial Ca²⁺ concentration is controlled by influx and efflux pathways: the former controlled by the activity of the mitochondrial Ca²⁺ uniporter (MCU), the latter by the Na⁺/Ca²⁺ exchanger (NCLX) and the H⁺/Ca²⁺ (mHCX) exchanger. The molecular identities of MCU and of NCLX have been recently unraveled, thus allowing genetic studies on their physiopathological relevance. After a general framework on the significance of mitochondrial Ca²⁺ uptake, this review discusses the structure of the MCU complex and the regulation of its activity, the importance of mitochondrial Ca²⁺ signaling in different physiological settings, and the consequences of MCU modulation on organ physiology.

Pyrazinamide susceptibility testing: proposed new standard with the BACTECTM MGITTM 960 system

The susceptibility of 253 Mycobacterium tuberculosis complex isolates to pyrazinamide (PZA) was assessed using the BACTECTM MGITTM 960 (M960) system. Resistant strains underwent paired repeat testing using 1) a critical concentration of 200 g/ml (PZA-200), and 2) a reduced inoculum of 0.25 ml. They were also examined using the BACTEC 460 (B460) reference method and investigated for pncA mutations. On M960, 37 isolates were resistant. In the PZA-200 assay, 20 of these were resistant and 17 susceptible, while 18 were resistant and 19 susceptible with reduced inoculum. The B460 assay and pncA sequencing confirmed results with reduced inoculum.

Physical exercise in aging human skeletal muscle increases mitochondrial calcium uniporter expression levels and affects mitochondria dynamics

Age‐related sarcopenia is characterized by a progressive loss of muscle mass with decline in specific force, having dramatic consequences on mobility and quality of life in seniors. The etiology of sarcopenia is multifactorial and underlying mechanisms are currently not fully elucidated. Physical exercise is known to have beneficial effects on muscle trophism and force production. Alterations of mitochondrial Ca²⁺ homeostasis regulated by mitochondrial calcium uniporter (MCU) have been recently shown to affect muscle trophism in vivo in mice. To understand the relevance of MCU‐dependent mitochondrial Ca²⁺ uptake in aging and to investigate the effect of physical exercise on MCU expression and mitochondria dynamics, we analyzed skeletal muscle biopsies from 70‐year‐old subjects 9 weeks trained with either neuromuscular electrical stimulation (ES) or leg press. Here, we demonstrate that improved muscle function and structure induced by both trainings are linked to increased protein levels of MCU. Ultrastructural analyses by electron microscopy showed remodeling of mitochondrial apparatus in ES‐trained muscles that is consistent with an adaptation to physical exercise, a response likely mediated by an increased expression of mitochondrial fusion protein OPA1. Altogether these results indicate that the ES‐dependent physiological effects on skeletal muscle size and force are associated with changes in mitochondrial‐related proteins involved in Ca²⁺ homeostasis and mitochondrial shape. These original findings in aging human skeletal muscle confirm the data obtained in mice and propose MCU and mitochondria‐related proteins as potential pharmacological targets to counteract age‐related muscle loss.

Role of p66shc in skeletal muscle function

p66shc is a growth factor adaptor protein that contributes to mitochondrial ROS production. p66shc is involved in insulin signaling and its deletion exerts a protective effect against diet-induced obesity. In light of the role of skeletal muscle activity in the control of systemic metabolism and obesity, we investigated which is the contribution of p66shc in regulating muscle structure and function. Here, we show that p66shc^−/− muscles are undistinguishable from controls in terms of size, resistance to denervation-induced atrophy, and force. However, p66shc^−/− mice perform slightly better than wild type animals during repetitive downhill running. Analysis of the effects after placing mice on a high fat diet (HFD) regimen demonstrated that running distance is greatly reduced in obese wild type animals, but not in overweight-resistant p66shc^−/− mice. In addition, muscle force measured after exercise decreases upon HFD in wild type mice while p66shc^−/− animals are protected. Our data indicate that p66shc affect the response to damage of adult muscle in chow diet, and it determines the maintenance of muscle force and exercise performance upon a HFD regimen.

Structure, Activity Regulation, and Role of the Mitochondrial Calcium Uniporter in Health and Disease

Mitochondrial Ca²⁺ uptake plays a pivotal role both in cell energy balance and in cell fate determination. Studies on the role of mitochondrial Ca²⁺ signaling in pathophysiology have been favored by the identification of the genes encoding the mitochondrial calcium uniporter (MCU) and its regulatory subunits. Thus, research carried on in the last years on one hand has determined the structure of the MCU complex and its regulation, on the other has uncovered the consequences of dysregulated mitochondrial Ca²⁺ signaling in cell and tissue homeostasis. Whether mitochondrial Ca²⁺ uptake can be exploited as a weapon to counteract cancer progression is debated. In this review, we summarize recent research on the molecular structure of the MCU, the regulatory mechanisms that control its activity and its relevance in pathophysiology, focusing in particular on its role in cancer progression.

Calcium at the Center of Cell Signaling: Interplay between Endoplasmic Reticulum, Mitochondria, and Lysosomes

In recent years, rapid discoveries have been made relating to Ca²⁺ handling at specific organelles that have important implications for whole-cell Ca²⁺ homeostasis. In particular, the structures of the endoplasmic reticulum (ER) Ca²⁺ channels revealed by electron cryomicroscopy (cryo-EM), continuous updates on the structure, regulation, and role of the mitochondrial calcium uniporter (MCU) complex, and the analysis of lysosomal Ca²⁺ signaling are milestones on the route towards a deeper comprehension of the complexity of global Ca²⁺ signaling. In this review we summarize recent discoveries on the regulation of interorganellar Ca²⁺ homeostasis and its role in pathophysiology.

Decline in macrolide resistance rates among Streptococcus pyogenes causing pharyngitis in children isolated in Italy

Macrolides are often used to treat group A streptococcus (GAS) infections, but their resistance rates reached high proportions worldwide. The aim of the present study was to give an update on the characteristics and contemporary prevalence of macrolide-resistant pharyngeal GAS in Central Italy. A total of 592 isolates causing pharyngitis in children were collected in the period 2012–2013. Clonality was assessed by emm typing and pulsed-field gel electrophoresis (PFGE) for all macrolide-resistant strains and for selected susceptible isolates. Genetic determinants of resistance were screened by polymerase chain reaction (PCR). Forty-four GAS were erythromycin-resistant (7.4 %). Among them, 52.3 % and 50 % were clindamycin- and tetracycline-resistant, respectively. erm(B)-positive isolates (52.3 %) expressed the constitutive cMLS_B phenotype. mef(A) and its associated M phenotype were recorded in 40.9 % of the cases. The remaining erm(A)-positive isolates expressed the iMLS_B phenotype. Seventeen tetracycline-resistant isolates carried tet(M) and five isolates carried tet(O). Twenty-five emm types were found among all strains, with the predominance of emm types 12, 89, 1, and 4. Eleven emm types and 12 PFGE clusters characterized macrolide-resistant strains, with almost two-thirds belonging to emm12, emm4, and emm11. Macrolide-susceptible and -resistant emm types 12, 89, 11, and 4 shared related PFGE profiles. There was a dramatic decline in macrolide resistance in Central Italy among pharyngeal GAS isolates in 2012–2013 when compared to previous studies from the same region (p < 0.05), although macrolide consumption remained stable over the past 15 years. We observed a decrease in the proportion of macrolide-resistant strains within emm types commonly associated with macrolide resistance in the past, namely emm12, 1, and 89.

Corynebacterium glucuronolyticum causing genitourinary tract infection: Case report and review of the literature

Corynebacterium species are increasingly recognized as opportunistic pathogens. A growing number of taxonomic studies has yielded a description of numerous new Corynebacterium species, such as those related to the urogenital tract, with Corynebacterium glucuronolyticum found to be rarely involved in genitourinary tract infections, particularly in male individuals. In this report, we describe a urethritis case caused by C. glucuronolyticum in a 37-year-old, apparently healthy male, who complained mild pain in the lower abdomen, with several urinary symptoms. While urethral and semen specimens did not yield positive results for microbiological evaluation, cultures of urine samples revealed the monomicrobial growth on blood-containing media of tiny colonies after 24 h of incubation, clearly evident only after 48 h of incubation under CO2-enriched atmosphere. Colonies were identified as C. glucuronolyticum both by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) and 16S rRNA gene sequencing. Oral ciprofloxacin gradually led to clinical improvement and, finally, to a complete recovery, in accordance with microbiological findings. In spite of its infrequent detection, C. glucuronolyticum might be a potential urogenital pathogen in males more commonly that what believed, perhaps due to slow growth leading to underrecognition; we suggest therefore to consider the organism in the differential diagnostics of bacterial diseases of the urinary tract.

The mitochondrial calcium uniporter controls skeletal muscle trophism in vivo

Muscle atrophy contributes to the poor prognosis of many pathophysiological conditions, but pharmacological therapies are still limited. Muscle activity leads to major swings in mitochondrial [Ca(2+)], which control aerobic metabolism, cell death, and survival pathways. We investigated in vivo the effects of mitochondrial Ca(2+) homeostasis in skeletal muscle function and trophism by overexpressing or silencing the mitochondrial calcium uniporter (MCU). The results demonstrate that in both developing and adult muscles, MCU-dependent mitochondrial Ca(2+) uptake has a marked trophic effect that does not depend on aerobic control but impinges on two major hypertrophic pathways of skeletal muscle, PGC-1α4 and IGF1-Akt/PKB. In addition, MCU overexpression protects from denervation-induced atrophy. These data reveal a novel Ca(2+)-dependent organelle-to-nucleus signaling route that links mitochondrial function to the control of muscle mass and may represent a possible pharmacological target in conditions of muscle loss.

Antimicrobial Susceptibility, Biochemical and Genetic Profiles ofStaphylococcus haemolyticusStrains Isolated from the Bloodstream of Patients Hospitalized in Critical Care Units

Staphylococcus haemolyticus strains (n=20), responsible of blood stream infections, were consecutively isolated from patients hospitalized in two different wards at high risk of infection. Strains displayed high rate of resistance to oxacillin (90%). All strains but two with decreased susceptibility (MIC = 4 microg/mL), were sensitive to vancomycin. Ten strains were resistant to teicoplanin. Among the strains susceptible to glycopeptides, three displayed heteroresistance to vancomycin and seven to teicoplanin, when tested by Etest technique with 2 x McFarland inoculum. Biochemical reactions allowed to assign strains to eight biotypes, with 11 strains clustering under two main biotype A and biotype B. Pulsed-field-gel-electrophoresis (PFGE) identified 11 different PFGE-types. Seven strains grouping under the major PFGE-type 1 and three strains clustering in PFGE-type 2, closely correlated to biotype A and biotype B respectively. Seven teicoplanin-resistant isolates clustered in the PFGE-type 1, two in the PFGE-type 2 and one in PFGE-type 5. Therefore, teicoplanin-resistant strains were biochemically and genetically related and clonally distributed, despite different clones of S. haemolyticus circulated in the units during the study period.

Tuberculous meningoencephalitis in a patient with hairy cell leukemia in complete remission

Tuberculous meningoencephalitis is a rare disease associated with high morbidity and mortality. We report a patient with hairy cell leukemia in complete remission who, after a single cycle of chemotherapy with cladribine, presented fever and neurological deficits. Laboratory diagnosis of tuberculous meningoencephalitis was made by polymerase chain reaction testing for Mycobacterium tuberculosis in cerebrospinal fluid. Despite the prompt institution of antitubercular-therapy, patient's general condition did not improve and he died. Mycobacterial infection should be considered in patients with intra-cranial lesions, affected by hematological malignancies and persistent immunosuppression.

THE NATURE AND CONTROL OF REACTIONS IN BIOLUMINESCENCE : WITH SPECIAL REFERENCE TO THE MECHANISM OF REVERSIBLE AND IRREVERSIBLE INHIBITIONS BY HYDROGEN AND HYDROXYL IONS, TEMPERATURE, PRESSURE, ALCOHOL, URETHANE, AND SULFANILAMIDE IN BACTERIA

On the basis of available data with regard to the chemical and physical properties of the "substrate" luciferin (LH₂) and enzyme, luciferase (A), and of kinetic data derived both from the reaction in extracts of Cypridina, and from the luminescence of intact bacteria, the fundamental reactions involved in the phenomenon of bioluminescence have been schematized. These reactions provide a satisfactory basis for interpreting the known characteristics of the system, as well as the theoretical chemistry with regard to the control of its over-all velocity in relation to various factors. These factors, here studied experimentally wholly with bacteria, Photobacterium phosphoreum in particular, include pH, temperature, pressure, and the drugs sulfanilamide, urethane, and alcohol, separately and in relation to each other. Under steady state conditions of bacterial luminescence, with excess of oxidizable substrate and with oxygen not limiting, the data indicate that the chief effects of these agents center around the pace setting reactions, which may be designated by the equation: A + LH₂ → ALH₂ following which light emission is assumed proportional to the amount of the excited molecule, AL*. The relation between pH and luminescence intensity varies with (a), the buffer mixture and concentration, (b), the temperature, and (c), the hydrostatic pressure. At an optimum temperature for luminescence of about 22° C. in P. phosphoreum, the effects of increasing or decreasing the hydrogen ion concentration are largely reversible over the range between pH 3.6 and pH 8.8. The relation between luminescence intensity and pH, under the experimental conditions employed, is given by the following equation, in which I₁ represents the maximum intensity, occurring about pH 6.5; I₂ the intensity at any other given pH; K₅ the equilibrium constant between hydrogen ions and the AL_-; and K₆ the corresponding constant with respect to hydroxyl ions: See PDF for Equation The value of K₅, as indicated by the data, amounts to 4.84 x 10⁴, while that of K₆ amounts to 4.8 x 10⁵. Beyond the range between approximately pH 3.8 and 8.8, destructive effects of the hydrogen and hydroxyl ions, respectively, were increasingly apparent. By raising the temperature above the optimum, the destructive effects were apparent at all pH, and the intensity of the luminescence diminished logarithmically with time. With respect to pH, the rate of destruction of the light-emitting system at temperatures above the optimum was slowest between pH 6.5 and 7.0, and increased rapidly with more acid or more alkaline reactions of the medium. The reversible effects of slightly acid pH vary with the temperature in the manner of an inhibitor (Type I) that acts independently of the normal, reversible denaturation equilibrium (K₁) of the enzyme. The per cent inhibition caused by a given acid pH in relation to the luminescence intensity at optimum pH, is much greater at low temperatures, and decreases as the temperature is raised towards the optimum temperature. The observed maximum intensity of luminescence is thus shifted to slightly higher temperatures by increase in (H⁺). The apparent activation energy of luminescence is increased by a decrease in pH. The value of ΔH‡ at pH 5.05 was calculated to be 40,900 calories, in comparison with 20,700 at a pH of 6.92. The difference of 20,200 is taken to represent an estimate of the heat of ionization of ALH in the activation process, and compares roughtly with the 14,000 calories estimated for the same process, by analyzing the data from the point of view of hydrogen ions as an inhibitor. The decreasing temperature coefficient for luminescence in proceeding from low temperatures towards the optimum is accounted for in part by the greater degree of ionization of ALH. At the optimum temperature and acid reactions, pressures up to about 500 atmospheres retard the velocity of the luminescent oxidation. At the same temperature, with decrease in hydrogen ion concentration, the pressure effect is much less, indicating a considerable volume increase in the process of ionization and activation. In the extremely alkaline range, beyond pH 9, luminescence is greatly reduced, as compared with the intensity at neutrality, and under these conditions pressure causes a pronounced increase in intensity, presumably by acting upon the reversible denaturation equilibrium of the protein enzyme, A. Sulfanilamide, in neutral solutions, acts on luminescence in a manner very much resembling that of hydrogen ions at acidities between pH 4.0 and pH 6.5. Like the hydrogen ion equilibrium, the sulfanilamide equilibrium involves a ratio of approximately one inhibitor molecule to one enzyme molecule. The heat of reaction amounts to about 11,600 calories or more in a reversible combination that evidently evolves heat. Like the action of H ions, sulfanilamide causes a slight shifting of maximum luminescence intensity in the direction of higher temperatures, and an increase in the energy of activation. The effect of sulfanilamide on the growth of broth cultures of eight species of luminous bacteria indicates that there is no regular relationship among the different organisms between the concentration of the drug that prevents growth, and that which prevents luminescence in the cells which develop in the presence of sulfanilamide. p-Aminobenzoic acid (PAB) antagonizes the sulfanilamide inhibition of growth in luminous bacteria, and the cultures that develop are luminous. When (PAB) is added to cells from fully developed cultures, it has no effect on luminescence, or causes a slight inhibition, depending on the concentration. With luminescence partly inhibited by sulfanilamide, the addition of PAB has no effect, or has an inhibitory effect which adds to that caused by sulfanilamide. Two different, though possibly related, enzyme systems thus appear to limit growth and luminescence, respectively. The possible mechanism through which both the inhibitions and the antagonism take place is discussed. The irreversible destruction of the luminescent system at temperatures above that of the maximum luminescence, in a medium of favorable pH to which no inhibitors have been added, proceeds logarithmically with time at both normal and increased hydrostatic pressures. Pressure retards the rate of the destruction, and the analysis of the data indicates that a volume increase of roughly 71 cc. per gm. molecule at 32° C. takes place in going from the normal to the activated state in this reaction. At normal pressure, the rate of destruction has a temperature coefficient of approximately 90,000 calories, or about 20,000 calories more than the heat of reaction in the reversible denaturation equilibrium. The data indicate that the equilibrium and the rate process are two distinct reactions. The equation for luminescence intensity, taking into account both the reversible and irreversible phases of the reaction is given below. In the equation b is a proportionality constant; k' the rate constant of the luminescent reaction; A₀ the total luciferase; A_0i the total initial luciferase at time t equals 0; k_n the rate constant for the destruction of the native, active form of the enzyme; k_d the rate constant for the destruction of the reversibly denatured, inactive form; t the time; and the other symbols are as indicated above: See PDF for Equation For reasons cited in the text, k_n evidently equals k_d. Urethane and alcohol, respectively, act in a manner (Type II) that promotes the breaking of the type of bonds broken in both the reversible and irreversible reactions and so promotes the irreversible denaturation. This result is in contrast to the effects of sulfanilamide, which at appropriate concentrations may give rise to the same initial inhibition as that caused by urethane, but remains constant with time. The inhibition caused by urethane and alcohol, respectively, increases as the temperature is raised. As a result, the apparent optimum is shifted to lower temperatures, and the activation energy for the over-all process of luminescence diminishes. An analysis for the approximate heat of reaction in the equilibrium between these drugs and the enzyme, indicates 65,000 calories for urethane, and 37,000 for alcohol. A similar analysis with respect to the effect of hydroxyl ions as the inhibitor gives 60,300 calories. The effects of alcohol and urethane are sensitive to hydrostatic pressure. Moderate inhibitions at optimum temperature and pH, caused by relatively small concentrations of either drug, are completely abolished by pressures of 3,000 to 4,000 pounds per square inch. At optimum temperature and pH, increasing concentrations of alcohol caused the apparent optimum pressure for luminescence to shift markedly in the direction of higher pressures. Analysis of the data with respect to concentration of alcohol at different pressures indicated that the ratio of alcohol to enzyme molecules amounted to approximately 4, at 7,000 pounds, but only about 2.8 at normal pressures. This phenomenon was taken to indicate that more than one equilibrium is established between the alcohol and the protein. A similar interpretation was suggested in connection with the fact that analysis of the relation between concentration of urethane and amount of inhibition at different temperatures also indicated a ratio of urethane to enzyme molecules that increased with temperature in the equilibria involved. Analysis of the data with respect to pressure and the inhibition caused by a given concentration of alcohol at different temperatures indicated that the volume change involved in the combination of alcohol with the enzyme must be very small, while the actual effect of pressure is apparently mediated through the reversible denaturation of the protein enzyme, which is promoted by alcohol, urethane, and drugs of similar type.

Molecular characterisation and clonal analysis of group A streptococci causing pharyngitis among paediatric patients in Palermo, Italy

Group A streptococci (n = 123), isolated consecutively from paediatric patients with pharyngitis from Palermo, Italy, were analysed. The emm and sof genes were sequenced, the presence of the speA and speC genes was investigated, and the macrolide resistance phenotypes and genotypes were determined. A limited number of emm/sof genotypes was found, and the most prevalent types were different from those found in a previous study from Rome. Macrolide resistance was found in the most prevalent clones, suggesting that the spread of mobile antibiotic resistance genes among the fittest clones in the community was the main mechanism influencing macrolide resistance rates in different emm types.

Clonality AmongEnterococcus faeciumClinical Isolates

In the course of a survey to determine the epidemiology of enterococcal infections in Italy, a sudden increment, in a 1-year time, was noted in the number of glycopeptide resistant Enterococcus faecium isolated from different wards of the University Hospital in Rome, Italy. The isolates were characterized for clonal relatedness by comparing SmaI gel electropherotypes, presence of vancomycin-resistance genes, and expression of virulence factors. PFGE identified in a single pulsed type all the glycopeptide-resistant isolates but one. Resistance to high levels of aminoglycosides was expressed by these same isolates, which also included a majority of non biofilm-forming strains. Two esp gene-carrying strains were also identified in different PFGE types. Data indicates that a specific clone acquired, in the clinical setting, the genetic determinant for glycopeptide resistance, thus improving environmental adaptation and favoring its persistence and spread.

Mifepristone (RU 38486) influences expression of glycoprotein Po and morphological parameters at the level of rat sciatic nerve: in vivo observations

The observations here reported indicate that, in vivo, the expression of an important protein of peripheral myelin, the glycoprotein Po, is influenced by mifespristone (RU 38486), that is, an antagonist of progesterone (PR) and glucocorticoid (GR) receptor. In our experimental model, male rats have been treated at the first day of life with this antagonist and after repeated treatments, we have analyzed in the sciatic nerve of 20- (20d) and 30-day-old rats (30d) the mRNA and protein levels of Po. Moreover, expression of Po has also been analyzed in the sciatic nerve of animals treated during the first 30 days of postnatal life and then sacrificed at 90th day of life (90d). The results obtained have indicated that both mRNA and protein levels of Po decrease at 20d. Apparently, these effects seem to be transient because no changes are evident at the other two times of analysis. As shown by morphometric analysis, the treatment with RU 38486 is also able to induce morphological changes at the level of sciatic nerve. However, at variance to what is expected by an alteration of an important component of the myelin membranes like Po, no changes are evident at the level of the myelin compartment. On the contrary, a significant reduction of axon diameter in parallel to an increase in neurofilament (NF) density occurs since 30d. In conclusion, the present data seem to suggest that progestin and/or glucocorticoid signals are not only involved in the control of myelin compartment but also on the axon maintenance.

Enterococcus spp. produces slime and survives in rat peritoneal macrophages

Enterococcal clinical isolates were investigated for the ability to form biofilm on inert surfaces, as a measure of slime production, in an attempt to find new possible virulence factors for these microorganisms. This property was commonly found among Enterococcus faecalis. Also E. faecium isolates were able to form biofilm, although to a lesser extent; for this species, however, biofilm formation seemed more frequently associated with isolates from infection rather than with environmental strains or isolates from healthy individuals. Biofilm formation was strongly affected by the presence of an additional carbohydrate source in the medium, or by iron deprivation, indicating a role of slime for survival in stressful conditions. Slime-producing E. faecalis were able to survive inside peritoneal macrophages for extended periods compared to slime-negative strains or to slime-positive bacteria grown in conditions depressing slime production. In particular, slime-producing and slime-negative cells showed a decrease of 1 and 2 log units, respectively, at 1 h after infection; slime-negative cells were then rapidly killed, with clearance of bacterial cells at 24 h. Slime-producing bacteria persisted up to 48 h, which was the last time point examined, as after that time viability of both infected and non-infected macrophages started to decline. Scanning electron microscopy observations showed the presence of abundant amorphous extracellular material, of possible polysaccharide nature, embedding bacterial cells to form a multilayered biofilm. Even in conditions not supporting biofilm formation, bacterial cells appeared capsulated, suggesting that capsule and slime might represent different structures. Genes belonging to the epa locus or to a putative icaA homolog did not seem to be involved in synthesis and export of slime.

Antibiotic resistance and genotypic characterization by PFGE of clinical and environmental isolates of enterococci

Fifty-four Enterococcus faecalis and 20 Enterococcus faecium isolates from clinical and non-human sources in Rome, Italy, were characterized by antibiotic resistance and pulsed field gel electrophoresis (PFGE). Resistance to vancomycin, teicoplanin, ampicillin, and ciprofloxacin was more frequent in E. faecium than in E. faecalis, whereas high-level resistance to aminoglycoside was found primarily in E. faecalis. Multi-resistance was found primarily among clinical isolates, but was also observed among environmental isolates. Common genotypes shared among clinical and environmental isolates were observed, however, the majority of isolates occurred as unique, source-specific clones. Several PFGE types were associated with shared features in their antibiotic resistance patterns; evidences of clonal spread between and within wards were also noted. This is the first report indicating clonal relatedness between human and environmental enterococci isolated in Italy.

Seriate histomorphometry of whole rat stomach: an accurate and reliable method for quantitative analysis of mucosal damage

The evaluation of mucosal damage in experimental models of gastric injury is commonly based on macroscopic detection of gross lesions and/or histological examination of tissue samples and is limited by the subjectivity of the examiner and by the paucity of nonrepresentative samples. This study proposes a novel method for the histomorphometric analysis of gastric damage, based on the examination of seriate parallel strips taken from whole rat stomachs. Strips were cut perpendicular to the lesser curvature, placed on a glass slide, with the side of each strip distal to the pylorus upward, and processed for routine histology. Sections were then observed by light microscopy: the length of damaged mucosa divided by the total length of mucosa, measured on a micrometric scale and expressed in percentage values, was indicated as the lesion index. Furthermore, to evaluate the severity of the damage, three types of lesions were discriminated depending on their depth: type I, lysis of luminal cells; type II, damage involving the cells lying on both surface mucosa and gastric pits; and type III, damage involving the lower part of the lamina propria with injury of glands associated with detachment of whole mucosal layers. Three models of acute gastric damage (ethanol, hemorrhagic shock, and indomethacin) were examined and treatment was also carried out with the antiulcer drugs omeprazole, ranitidine, and misoprostol, to show the advantages of this histomorphometric approach. The results indicate that this method allows an accurate quantitative analysis of gastric damage, and the effects of different antiulcer drugs can be better discriminated.

Group A streptococcal genotypes from pediatric throat isolates in Rome, Italy

In a study assessing genetic diversity, 114 group A streptococcus (GAS) isolates were recovered from pediatric pharyngitis patients in Rome, Italy. These isolates comprised 22 different M protein gene (emm) sequence types, 14 of which were associated with a distinct serum opacity factor/fibronectin binding protein gene (sof) sequence type. Isolates with the same emm gene sequence type generally shared a highly conserved chromosomal macrorestriction profile. In three instances, isolates with dissimilar macrorestriction profiles had identical emm types; in each of these cases multilocus sequence typing revealed that isolates with the same emm type were clones having the same allelic profiles. Ninety-eight percent of the pharyngeal isolates had emm types previously found to be highly associated with mga locus gene patterns commonly found in pharyngeal GAS isolates.

Necrotizing fasciitis due to penicillin-resistant Streptococcus pneumoniae: case report and review of the literature

Necrotizing fasciitis (NF) is a life-threatening infection involving rapid necrosis of subcutaneous and fascial tissues. Streptococcus pneumoniae (SPN) soft tissue infection is exceedingly uncommon, reported primarily in patients with immunosuppression or other underlying conditions. We report a case of NF and septic shock in a healthy 32-year-old man, whose only predisposing factor was antecedent blunt trauma. Pathological examination and culture of the extensive tissue debridement were positive only for SPN. The serotype 9V isolate was penicillin (PCN)-resistant (MIC=2.0), and closely-related by pulse field gel electrophoresis and multilocus fingerprinting to clone France 9V-3, an important genetic reservoir for increasing PCN-resistance worldwide. This unique case has implications for our pathogenic under-standing and empiric management of NF.

Routine molecular identification of enterococci by gene-specific PCR and 16S ribosomal DNA sequencing

For 279 clinically isolated specimens identified by commercial kits as enterococci, genotypic identification was performed by two multiplex PCRs, one with ddl(E. faecalis) and ddl(E. faecium) primers and another with vanC-1 and vanC-2/3 primers, and by 16S ribosomal DNA (rDNA) sequencing. For 253 strains, phenotypic and genotypic results were the same. Multiplex PCR allowed for the identification of 13 discordant results. Six strains were not enterococci and were identified by 16S rDNA sequencing. For 5 discordant and 10 concordant enterococcal strains, 16S rDNA sequencing was needed. Because many supplementary tests are frequently necessary for phenotypic identification, the molecular approach is a good alternative.