Introduction of cyclic AMP phosphodiesterase into rat submandibular acini prevents isoproterenol-stimulated cyclic AMP rise without affecting mucin secretion

Intracellular Delivery by Membrane Disruption: Mechanisms, Strategies, and Concepts

Intracellular delivery is a key step in biological research and has enabled decades of biomedical discoveries. It is also becoming increasingly important in industrial and medical applications ranging from biomanufacture to cell-based therapies. Here, we review techniques for membrane disruption-based intracellular delivery from 1911 until the present. These methods achieve rapid, direct, and universal delivery of almost any cargo molecule or material that can be dispersed in solution. We start by covering the motivations for intracellular delivery and the challenges associated with the different cargo types-small molecules, proteins/peptides, nucleic acids, synthetic nanomaterials, and large cargo. The review then presents a broad comparison of delivery strategies followed by an analysis of membrane disruption mechanisms and the biology of the cell response. We cover mechanical, electrical, thermal, optical, and chemical strategies of membrane disruption with a particular emphasis on their applications and challenges to implementation. Throughout, we highlight specific mechanisms of membrane disruption and suggest areas in need of further experimentation. We hope the concepts discussed in our review inspire scientists and engineers with further ideas to improve intracellular delivery.

A cyclic nucleotide PDE5 inhibitor corrects defective mucin secretion in submandibular cells containing antibody directed against the cystic fibrosis transmembrane conductance regulator protein

A selective cyclic nucleotide PDE5 inhibitor corrected the defective mucin secretion response to the beta-agonist isoproterenol in submandibular acinar cells inhibited by antibody directed against the cystic fibrosis transmembrane conductance regulator. The PDE5 inhibitor was as effective as cpt-cyclic AMP or a selective PDE4 inhibitor. However, the PDE5 inhibitor had no effect on basal or isoproterenol-stimulated cyclic AMP levels and did not stimulate mucin secretion. The results showing, for the first time, correction of the CFTR mucin secretion defect by a PDE5 inhibitor, which may involve cyclic GMP, will have a major impact in development of a rational drug treatment for cystic fibrosis.

Actions of adenosine A1 and A2 receptor antagonists on CFTR antibody-inhibited beta-adrenergic mucin secretion response

1. The cystic fibrosis gene protein, the cystic fibrosis transmembrane conductance regulator (CFTR) acts as a chloride channel and is a key regulator of mucin secretion. The mechanism by which 3-isobutyl-1-methylxanthine (IBMX) corrects the defect in CFTR mediated beta-adrenergic stimulation of mucin secretion has not been determined. The present study has investigated the actions of adenosine A1 and A2 receptor antagonists to determine whether ability to stimulate mucin secretion correlates with correction of CFTR antibody inhibited beta-adrenergic response and whether excessive cyclic AMP rise is required. 2. CFTR antibodies were introduced into living rat submandibular acini by hypotonic swelling. Following recovery, mucin secretion in response to isoproterenol was measured. 3. The adenosine A1 receptor antagonist, 8 cyclopentyltheophylline (CPT) was a less potent stimulator of mucin secretion than was the A2 receptor antagonist dimethylpropargylxanthine (DMPX). A concentration of CPT close to the Ki for A1 receptor antagonism (10 nM) did not stimulate mucin secretion. 4. DMPX, although a potent stimulator of mucin secretion, did not correct CFTR antibody inhibited mucin secretion. 5. CPT corrected defective CFTR antibody inhibited mucin secretion at a high (1 mM) concentration, suggesting a mechanism other than adenosine receptor antagonism. 6. DMPX potentiated the isoproterenol induced cyclic AMP rise, whereas CPT did not. 7. Correction of the defective CFTR mucin secretion response did not correlate with ability to stimulate mucin secretion and did not require potentiation of beta-adrenergic induced increases in cyclic AMP. This affords real promise for the development of a selective drug treatment for cystic fibrosis.

Atrial natriuretic factor modifies the composition of induced-salivary secretion in the rat

We have previously reported that although the atrial natriuretic factor (ANF) was not a sialogogic agonist, it enhanced cholinergic, alpha-adrenergic and peptidergic (substance P) stimulated salivation in the submaxillary and parotid gland of the rat. The purpose of the present work was to study whether ANF modified the composition of agonist-induced saliva in the rat. Results showed that in the submaxillary gland, ANF increased sodium and decreased potassium excretion when salivation was stimulated by methacholine (MC) or substance P (SP). However, when salivation was induced by methoxamine (MX), ANF only increased sodium excretion. On the other hand, in the parotid gland, ANF increased both sodium and potassium excretion when salivation was induced either by MC or SP but did not modify electrolyte output in MX induced salivary secretion. Protein output and amylase activity were not modified by the presence of ANF when the aforementioned sialogogic agonists were used to elicit salivation in either gland. Although ANF did not modify the volume of isoproterenol (IP) induced saliva, it increased protein output in both glands and it increased amylase activity in the parotid gland. The present results suggest that ANF may play a role in the modulation of salivary secretion in the parotid and submaxillary glands of the rat. ANF effect is likely to be mediated by modifications in the calcium level linked to phosphoinositide metabolism within the acinar and/or the ductal cells of the salivary glands.

An antibody against a CFTR-derived synthetic peptide, incorporated into living submandibular cells, inhibits beta-adrenergic stimulation of mucin secretion

An antibody raised against a peptide in the first nucleotide-binding domain (NBD) of CFTR [1], incorporated into intact rat submandibular acini by hypotonic swelling, inhibited beta-adrenergic stimulated mucin secretion, without affecting cyclic AMP rise. The data are the first to show that a CFTR-antibody-containing cell results in defective stimulation of mucin secretion, as is seen in CF cells, and that this can be reversed by an excessive increase in cyclic AMP.

Introduction of BAPTA into intact rat submandibular acini inhibits mucin secretion in response to cholinergic and beta-adrenergic agonists

Incorporation of the calcium chelator BAPTA into isolated, intact rat submandibular acini by hypotonic swelling, resulted in complete inhibition of carbamylcholine, noradrenaline and isoproterenol stimulation of mucin secretion. No effects of intracellular BAPTA on cell viability or beta-adrenergic stimulation of cyclic AMP formation were observed. The data are the first to demonstrate that calcium is necessary for beta-adrenergic stimulation of secretion and suggest that Ca2+ provides a common link in the triggering of exocytosis.