Cross-talk between apoptosis and autophagy in lung epithelial cell death

Abstract: As an essential organ for gas exchange, the lungs are constantly exposed to the external environment and are simulated by toxicants and pathogens. The integrity of lung epithelium and epithelial cells is crucial for fulfilling the physiological functions of the lung. The homeostasis of lung epithelial cells is maintained by a complex network by which survival and death are tightly regulated. Upon noxious stimulation, lung epithelium attempts to maintain its normal structure and function. Savage of injured cells and clearance of unsalvageable dying cells or unwanted proliferated cells constantly occur in the lung epithelium. Apoptosis, or programmed cell death, functions as a primary mechanism to discard unsalvageable cells or unwanted overgrowth. Autophagy, on the other hand, initially attempts to save and repair the injured cells. However, when the noxious stimulation is too strong and cell survival becomes unfeasible, autophagy behaves oppositely and cooperates with apoptosis, subsequently accelerates cell death. The imbalance between autophagy and apoptosis potentially leads to tumorigenesis or devastating cell death/lung injury. Therefore, the cross-talk between apoptosis and autophagy in lung epithelial cells is critical in determining the fate of epithelial cells and its balance of death/survival in response to environmental stimuli. In this review, we will focus on the current understandings of the communications between apoptosis and autophagy in lung epithelial cells. We will review multiple key regulators and their underlying mechanisms involved in the cross-talk between apoptosis and autophagy. The autophagic factors, such as the Beclin-1, ATG5, Fap-1, p62 and concentration-dependent LC3B, all closely interact with multiple apoptosis pathways. Understanding these regulations of apoptosis / autophagy cross-talk potentially provides novel targets for developing diagnostic and therapeutic strategies for many lung diseases, including lung injuries and malignancies

Exosome markers associated with immune activation and oxidative stress in HIV patients on antiretroviral therapy

Exosomes are nanovesicles released from most cell types including immune cells. Prior studies suggest exosomes play a role in HIV pathogenesis, but little is known about exosome cargo in relation to immune responses and oxidative stress. Here, we characterize plasma exosomes in HIV patients and their relationship to immunological and oxidative stress markers. Plasma exosome fractions were isolated from HIV-positive subjects on ART with suppressed viral load and HIV-negative controls. Exosomes were characterized by electron microscopy, nanoparticle tracking, immunoblotting, and LC-MS/MS proteomics. Plasma exosomes were increased in HIV-positive subjects compared to controls, and correlated with increased oxidative stress markers (cystine, oxidized cys-gly) and decreased PUFA (DHA, EPA, DPA). Untargeted proteomics detected markers of exosomes (CD9, CD63, CD81), immune activation (CD14, CRP, HLA-A, HLA-B), oxidative stress (CAT, PRDX1, PRDX2, TXN), and Notch4 in plasma exosomes. Exosomal Notch4 was increased in HIV-positive subjects versus controls and correlated with immune activation markers. Treatment of THP-1 monocytic cells with patient-derived exosomes induced expression of genes related to interferon responses and immune activation. These results suggest that exosomes in ART-treated HIV patients carry proteins related to immune activation and oxidative stress, have immunomodulatory effects on myeloid cells, and may have pro-inflammatory and redox effects during pathogenesis

Exosome markers associated with immune activation and oxidative stress in HIV patients on antiretroviral therapy

Exosomes are nanovesicles released from most cell types including immune cells. Prior studies suggest exosomes play a role in HIV pathogenesis, but little is known about exosome cargo in relation to immune responses and oxidative stress. Here, we characterize plasma exosomes in HIV patients and their relationship to immunological and oxidative stress markers. Plasma exosome fractions were isolated from HIV-positive subjects on ART with suppressed viral load and HIV-negative controls. Exosomes were characterized by electron microscopy, nanoparticle tracking, immunoblotting, and LC-MS/MS proteomics. Plasma exosomes were increased in HIV-positive subjects compared to controls, and correlated with increased oxidative stress markers (cystine, oxidized cys-gly) and decreased PUFA (DHA, EPA, DPA). Untargeted proteomics detected markers of exosomes (CD9, CD63, CD81), immune activation (CD14, CRP, HLA-A, HLA-B), oxidative stress (CAT, PRDX1, PRDX2, TXN), and Notch4 in plasma exosomes. Exosomal Notch4 was increased in HIV-positive subjects versus controls and correlated with immune activation markers. Treatment of THP-1 monocytic cells with patient-derived exosomes induced expression of genes related to interferon responses and immune activation. These results suggest that exosomes in ART-treated HIV patients carry proteins related to immune activation and oxidative stress, have immunomodulatory effects on myeloid cells, and may have pro-inflammatory and redox effects during pathogenesis

Summarized effects of PEG-cholesterol, PEG and cholesterol (MβCD) on <i>I</i>_Ca,L, r₅₀₀, V_0.5 of f_∞/V and <i>I</i>_WD.

<p>(<b>A</b>), Maximal <i>I</i>_Ca,L density; (<b>B</b>), r₅₀₀ obtained at 0 mV (<b>C</b>), the V_0.5 of f_∞/V relationship as averaged value of that obtained in each experiment. (<b>D</b>), averaged value of maximal density of the <i>I</i>_WD obtained in each experiment by multiplying <i>I</i>_Ca,L density and f_∞ value. The numerical values represent mean ± S.E.M. n: control, 37; 10 mM-PEG, 14; PEG-cholesterol; 0.1 mM, 9, 0.3 mM, 14, 1 mM, 15, 3 mM, 12 and 10 mM, 9; cholesterol (MβCD): n = 9 for both 1.3 and 4 mM. Statistical comparison was performed using ordinary one-way ANOVA followed by Dunnett's test; *, <i>p</i><0.05, **, <i>p</i><0.01, ***, <i>p</i><0.001, ****, <i>p</i><0.0001.</p

Caveolae, caveolin-1 and cavin-1: Emerging roles in pulmonary hypertension

Caveolae are flask-shaped invaginations of cell membrane that play a significant structural and functional role. Caveolae harbor a variety of signaling molecules and serve to receive, concentrate and transmit extracellular signals across the membrane. Caveolins are the main structural proteins residing in the caveolae. Caveolins and another category of newly identified caveolae regulatory proteins, named cavins, are not only responsible for caveolae formation, but also interact with signaling complexes in the caveolae and regulate transmission of signals across the membrane. In the lung, two of the three caveolin isoforms, i.e., cav-1 and -2, are expressed ubiquitously. Cavin protein family is composed of four proteins, named cavin-1 (or PTRF for polymerase Ⅰ and transcript release factor), cavin-2 (or SDPR for serum deprivation protein response), cavin-3 (or SRBC for sdr-related gene product that binds to-c-kinase) and cavin-4 (or MURC for muscle restricted coiled-coiled protein or cavin-4). All the caveolin and cavin proteins are essential regulators for caveolae dynamics. Recently, emerging evidence suggest that caveolae and its associated proteins play crucial roles in development and progression of pulmonary hypertension. The focus of this review is to outline and discuss the contrast in alteration of cav-1 (cav-1),-2 and cavin-1 (PTRF) expression and downstream signaling mechanisms between human and experimental models of pulmonary hypertension

Cross-talk between apoptosis and autophagy in lung epithelial cell death

Abstract: As an essential organ for gas exchange, the lungs are constantly exposed to the external environment and are simulated by toxicants and pathogens. The integrity of lung epithelium and epithelial cells is crucial for fulfilling the physiological functions of the lung. The homeostasis of lung epithelial cells is maintained by a complex network by which survival and death are tightly regulated. Upon noxious stimulation, lung epithelium attempts to maintain its normal structure and function. Savage of injured cells and clearance of unsalvageable dying cells or unwanted proliferated cells constantly occur in the lung epithelium. Apoptosis, or programmed cell death, functions as a primary mechanism to discard unsalvageable cells or unwanted overgrowth. Autophagy, on the other hand, initially attempts to save and repair the injured cells. However, when the noxious stimulation is too strong and cell survival becomes unfeasible, autophagy behaves oppositely and cooperates with apoptosis, subsequently accelerates cell death. The imbalance between autophagy and apoptosis potentially leads to tumorigenesis or devastating cell death/lung injury. Therefore, the cross-talk between apoptosis and autophagy in lung epithelial cells is critical in determining the fate of epithelial cells and its balance of death/survival in response to environmental stimuli. In this review, we will focus on the current understandings of the communications between apoptosis and autophagy in lung epithelial cells. We will review multiple key regulators and their underlying mechanisms involved in the cross-talk between apoptosis and autophagy. The autophagic factors, such as the Beclin-1, ATG5, Fap-1, p62 and concentration-dependent LC3B, all closely interact with multiple apoptosis pathways. Understanding these regulations of apoptosis / autophagy cross-talk potentially provides novel targets for developing diagnostic and therapeutic strategies for many lung diseases, including lung injuries and malignancies

Dehydroepiandrosterone (DHEA) Inhibits ICa,L and Window Current by Voltage-Dependent and Independent Mechanisms in Arterial Smooth Muscle Cells

Dehydroepiandrosterone (DHEA) is an adrenal steroid hormone, which has the highest serum concentration among steroid hormones with dehydroepiandrosterone sulfate (DHEAS). DHEA possesses inhibitory action on glucose-6-phosphate dehydrogenase (G6PD), the first pentose-phosphate pathway (PPP) enzyme that reduces NADP(+) to NADPH. DHEA induced relaxation of high K(+)-induced contraction in rat arterial strips, while DHEAS barely induced it. We studied the effects of DHEA on L-type Ca(2+) current (ICa,L) of A7r5 arterial smooth muscle cells (ASMCs) and compared the mechanism of inhibition with that produced by 6-aminonicotinamide (6-AN) competitive inhibitor of G6PD. DHEA moderately inhibited the ICa,L that was elicited from the holding potential (HP) of -80 mV (voltage-independent inhibition, VIDI) and accelerated decay of ICa,L during the depolarization pulse (voltage-dependent inhibition, VDI). DHEA-induced VDI decreased ICa,Lpeak at the depolarized HPs. By applying repetitive depolarization pulses from multiple HPs, novel HP-dependent steady-state inactivation curves (finfinity -HP) were constructed. DHEA shifted finfinity -HP to the left and inhibited the window current (IWD), which was recorded at depolarized HPs and obtained as product of I-V and finfinity -HP. IC50 of inhibition was much higher than serum concentration. DHEA-induced VDI was down-regulated by the dialysis of GDP-beta-S, which shifted finfinity -V to the right prior to the application of DHEA. 6-AN gradually and irreversibly inhibited ICa,L by VIDI, suggesting that the inhibition of G6PD is involved in DHEA-induced VIDI. In 6-AN-pretreated cells, DHEA induced additional inhibition by increasing VIDI and generating VDI. The inhibition of G6PD underlies DHEA-induced VIDI, and DHEA additionally induces VDI as described for Ca(2+) channel blockers