Chromogranins A and B are key proteins in amine accumulation, but the catecholamine secretory pathway is conserved without them

Chromogranins are the main soluble proteins in the large dense core secretory vesicles (LDCVs) found in aminergic neurons and chromaffin cells. We recently demonstrated that chromogranins A and B each regulate the concentration of adrenaline in chromaffin granules and its exocytosis. Here we have further studied the role played by these proteins by generating mice lacking both chromogranins. Surprisingly, these animals are both viable and fertile. Although chromogranins are thought to be essential for their biogenesis, LDCVs were evident in these mice. These vesicles do have a somewhat atypical appearance and larger size. Despite their increased size, single-cell amperometry recordings from chromaffin cells showed that the amine content in these vesicles is reduced by half. These data demonstrate that although chromogranins regulate the amine concentration in LDCVs, they are not completely essential, and other proteins unrelated to neurosecretion, such as fibrinogen, might compensate for their loss to ensure that vesicles are generated and the secretory pathway conserved.

Chromogranins as regulators of exocytosis

Chromogranins (Cgs) constitute the main protein component in the vesicular matrix of large dense core vesicles (LDCV). These acidic proteins have been implicated in several physiological processes such as vesicle sorting, the generation of bioactive peptides and the accumulation of soluble species inside LDCV. This latter feature of Cgs accounts for the ability of vesicles to concentrate catecholamines and Ca(2+). Indeed, the low affinity and high capacity of Cgs to bind solutes at the low pH of the LDCV lumen seems to be behind the delay in the neurotransmitter exit towards the extracellular milieu after vesicle fusion. The availability of new mouse strains lacking Cgs in combination with the arrival of several techniques for the direct monitoring of exocytosis (like amperometry, patch-amperometry and intracellular electrochemistry), have helped advance our understanding of how these granins concentrate catecholamines and Ca(2+) in LDCV, and how they influence the kinetics of exocytosis. In this review, we will discuss the roles of Cgs A and B in maintaining the intravesicular environment of secretory vesicles and in exocytosis, bringing together the most recent findings from adrenal chromaffin cells.

Chromogranins A and B as regulators of vesicle cargo and exocytosis

Chromogranins (Cgs) are acidic proteins that have been implicated in several physiological processes such as vesicle sorting, the production of bioactive peptides and the accumulation of soluble species inside large dense core vesicles (LDCV). They constitute the main protein component in the vesicular matrix of LDCV. This latter characteristic of Cgs accounts for the ability of vesicles to concentrate catecholamines and Ca(2+). It is likely that Cgs are behind the delay in the neurotransmitter exit towards the extracellular milieu after vesicle fusion, due to their low affinity and high capacity to bind solutes present inside LDCV. The recent availability of mouse strains lacking Cgs, combined with the arrival of several techniques for the direct monitoring of exocytosis, have helped to expand our knowledge about the mechanisms used by granins to concentrate catecholamines and Ca(2+) in LDCV, and how they affect the kinetics of exocytosis. We will discuss the roles of Cgs A and B in maintaining the intravesicular environment of secretory vesicles and in exocytosis, bringing together the most recent findings from adrenal chromaffin cells.

Extended enzymatic stability of reconstituted lyophilized PEG-asparaginase in vials

Asparaginase (ASNase) use as a tumour-inhibitor drug has changed completely the natural course of paediatric acute lymphoblastic leukaemia (ALL) in such a way that it represents a paradigm shift in ALL management. ASNase treatment emergence has significantly improved pathologic responses and increased survival rates of ALL patients. Although different ASNase forms are currently available, only the pegylated form (PEG-ASNase) is recommended by relevant clinic guides. PEG-ASNase form shows longer elimination half-life, reducing the number of administrations, along with an enhanced safety profile. In spite of all of these advantages, PEG-ASNase elevated cost limits enormously its use. PEG-ASNase is commercialised as a lyophilised powder which according to the manufacturer it is stable for 24 hours once reconstituted, as a result, the leftover is usually discarded. In this study we analysed the enzymatic stability of reconstituted PEG-ASNase after conservation in three different temperature conditions for 5 and 14 days, aiming to take advantage of the remaining leftover for the subsequent administration. Our results have shown that PEG-ASNase is stable at 4°C, -20°C and -80°C for at least 14 days, retaining the 95% from the initial enzymatic activity in all three storage temperatures. According to our results, it is feasible to reuse the remaining content of PEG-ASNase vial after reconstitution, which means a 50% reduction of its cost for paediatric patient treatment and, consequently, removes the main barrier to use this drug in a wider population.

MicroRNA-630: A promising avenue for alleviating inflammation in diabetic kidney disease

Diabetic kidney disease (DKD) is one of the complications of diabetes, affecting millions of people worldwide. The relentless progression of this condition can lead to kidney failure, requiring life-altering interventions such as dialysis or transplants. Accumulating evidence suggests that immunologic and inflammatory elements play an important role in initiating and perpetuating the damage inflicted on renal tissues, exacerbating the decline in organ function. Toll-like receptors (TLRs) are a family of receptors that play a role in the activation of the innate immune system by the recognition of pathogen-associated molecular patterns. Recent data from in vitro and in vivo studies have highlighted the critical role of TLRs, mainly TLR2 and TLR4, in the pathogenesis of DKD. In the diabetic milieu, these TLRs recognize diabetic-associated molecular signals, triggering a proinflammatory cascade that initiates and perpetuates inflammation and fibrogenesis in the diabetic kidney. Emerging non-traditional strategies targeting TLR signaling with potential therapeutic implications in DKD have been pro-posed. One of these approaches is the use of microRNAs, small non-coding RNAs that can regulate gene expression. This editorial comments on the results of this approach carried out in a rat model of diabetes by Wu et al, published in this issue of the World Journal of Diabetes. The results of the experimental study by Wu et al shows that microRNA-630 decreased levels compared to non-diabetic rats. Additionally, microRNA-630 exerted anti-inflammatory effects in the kidneys of diabetic rats through the modulation of TLR4. These findings indicate that the microRNA-630/TLR4 axis might represent a pathological mechanism of DKD and a potential therapeutic target capable of curbing the destructive inflammation characteristic of DKD.