HDAC6 Plays a Noncanonical Role in the Regulation of Antitumor Immune Responses, Dissemination, and Invasiveness of Breast Cancer

Despite the outstanding clinical results of immune checkpoint blockade (ICB) in melanoma and other cancers, clinical trials in breast cancer have reported low responses to these therapies. Current efforts are now focused on improving the treatment efficacy of ICB in breast cancer using new combination designs such as molecularly targeted agents, including histone deacetylase inhibitors (HDACi). These epigenetic drugs have been widely described as potent cytotoxic agents for cancer cells. In this work, we report new noncanonical regulatory properties of ultra-selective HDAC6i over the expression and function of epithelial-mesenchymal transition pathways and the invasiveness potential of breast cancer. These unexplored roles position HDAC6i as attractive options to potentiate ongoing immunotherapeutic approaches. These new functional activities of HDAC6i involved regulation of the E-cadherin/STAT3 axis. Pretreatment of tumors with HDAC6i induced critical changes in the tumor microenvironment, resulting in improved effectiveness of ICB and preventing dissemination of cancer cells to secondary niches. Our results demonstrate for the first time that HDAC6i can both improve ICB antitumor immune responses and diminish the invasiveness of breast cancer with minimal cytotoxic effects, thus departing from the cytotoxicity-centric paradigm previously assigned to HDACi. SIGNIFICANCE: Ultraselective HDAC6 inhibitors can reduce tumor growth and invasiveness of breast cancer by noncanonical mechanisms unrelated to the previously cytotoxic properties attributed to HDAC inhibitors.

Monodora myristica (African nutmeg) modulates redox homeostasis and alters functional chemistry in sickled erythrocytes

The antioxidative effect of Monodora myristica seed acetone extract and its effect on chemical functional groups were investigated in sickled erythrocytes as well as molecular modeling of the antisickling potentials of its secondary metabolites. The extract was subjected to gas chromatography–mass spectrometry to identify the compounds present, which were then docked into the allosteric-binding site of deoxy-hemoglobin. The extract was incubated with sickled erythrocytes at 37°C for 6, 12, and 24 h and were subjected to antioxidative analysis for reduced glutathione (GSH), superoxide dismutase (SOD), catalase, and lipid peroxidation (LPO). Chemical functional group of the treated cells was analyzed via Fourier transform infrared spectroscopy (FTIR). The predominant compounds identified were 17-octadecynoic acid; oleic acid, androstan-3-one, 17-hydroxy-2-methyl- (2.beta.,5.beta.,17.beta.)-; estran-3-one, 17-(acetyloxy)-2-methyl-, (2.alpha., 5.alpha., 17.beta.), and (+)-3-carene, 10-(acetylmethyl)-. They all fitted well within the active site of Hb with good binding affinity, as evidenced by the negative CDocker interaction energies of their complexes ranging between −54.4 and −26.7 kcal/mol. Treatment with the extract exacerbated SOD and catalase activities as well as GSH level, while LPO was suppressed. This antioxidative activity was time and/or dose dependent, with 6 and 12 h incubation showing the optimum activity. FTIR analysis of the treated cells showed the presence of hydrophobic functional groups. The synergetic molecular interaction of the major compounds of the extract with the α-dimer of Hb depicts an antisickling effect of M. myristica acetone extract. This is accompanied by exacerbation of endogenous antioxidant enzymes activity and modification of the functional chemistry of the cells.

An unusual tracheal foreign body - a case report

Foreign bodies in the laryngopharynx can occur without discrimination of age or sex. Their occurrence is influenced by mode of living, customs, habits and environment. T.M. Paramciwaran(1977) reported 56 cases of foreign bodies of tracheobronchial tree in the span of 5 years. A.S.A. Abdel-Salam and Alan G. Gibb (1980) mentioned that the vast majority of cases occur in young children. They have reported that undiagnosed foreign bodies cause mechanical effects, chemical reactions and may present as chronic pulmonary infection, allergic asthma, bronchiectasis, lung collapse or lung abscess. They present as emergencies and require skilful management.

Inhibiting the Na+/H+ exchanger reduces reperfusion injury: a small animal MRI study

We used magnetic resonance imaging (MRI) to assess the efficacy of Na+/H+ exchanger isoform 1 (NHE-1) inhibition following cerebral ischemia. Transient focal cerebral ischemia was induced in wild-type controls (NHE-1(+/+)), NHE-1 genetic knockdown mice (NHE-1(+/-)), and NHE-1(+/+) mice treated with the selective NHE-1 inhibitor HOE642. Diffusion weighted imaging (DWI) revealed a brain lesion as early as 1 hour following reperfusion and illustrated significant protection in NHE-1(+/-) mice (16.2 +/- 7.9 mm3 in NHE-1(+/-) mice vs. 47.5 +/- 16.6 mm3 in NHE-1(+/+) mice). Knockdown of NHE-1 showed significantly smaller infarct at 72 hours on T2 imaging (21.2 +/- 12.6 mm3 in NHE-1(+/-) mice vs. 64.6 +/- 2.5 mm3 in NHE-1(+/+) mice). Administration of HOE642 prior to reperfusion or during early reperfusion reduced ischemic damage. Thus, high resolution T2 images can be used for consistent and precise calculation of lesion volumes, while changes of DWI are a sensitive early marker of ischemic injury. The results of this study demonstrate the therapeutic potential for inhibition of NHE-1 in treating cerebral ischemia.

p90 activation contributes to cerebral ischemic damage via phosphorylation of Na+/H+ exchanger isoform 1

Excessive activation of Na+/H+ exchanger isoform 1 (NHE-1) plays a role in cerebral ischemic injury. The current study investigated whether NHE-1 protein in ischemic brains is regulated by extracellular signal-regulated kinase (ERK)/90-kDa ribosomal S6 kinase (p90(RSK)) signaling pathways. A transient focal ischemia in mice was induced by a 60-min-occlusion of the middle cerebral artery followed by reperfusion for 3, 10, or 60 min (Rp). Expression of phosphorylated ERK 1/2 was significantly elevated in the ipsilateral hemispheres at 3-10 min Rp and reduced by 60 min Rp. An increase in phosphorylation of p90(RSK), a known NHE-1 kinase, was also detected at 3-10 min Rp, which was accompanied with a transient elevation of NHE-1 phosphorylation (p-NHE-1). Stimulation of p90(RSK) in ischemic neurons was downstream of ERK activation because inhibition of MEK1 (MAP kinase/ERK kinase) with its inhibitor U0126 blocked phosphorylation of p90(RSK). Moreover, direct inhibition of p90(RSK) by its selective inhibitor fluoromethyl ketone not only reduced p-NHE-1 expression but also ischemic infarct volume. Taken together, our study revealed that reperfusion triggers a transient stimulation of the ERK/p90(RSK) pathway. p90(RSK) activation contributes to cerebral ischemic damage in part via activation of NHE-1 protein.

Hyperthyroidism induces apoptosis in rat liver through activation of death receptor-mediated pathways

BACKGROUND/AIMS

The molecular basis of hepatic dysfunction in thyrotoxicosis is not fully understood. Here, we investigated the effect of altered thyroidal status on death receptor pathways including p75 neurotrophin receptor (p75NTR), a member of tumor necrosis factor (TNF) receptor superfamily, in rat liver.

METHODS

Hyperthyroidism was induced in Sprague-Dawley rats by daily injections of triiodothyronine in a dose of 12.5 microg/100 g body weight for 10 days.

RESULTS

Terminal deoxynucleotide-transferase-mediated dUTP nick end labeling assay and caspase-3 activation data confirmed apoptosis in hyperthyroid rat liver. We observed the elevated levels of death ligands, TNF-alpha, Fas ligand and their cognate receptors, TNF-receptor-1 and Fas, and 8-fold increase in caspase-8 activation in hyperthyroid rat liver (p<0.001). We demonstrated for the first time that hyperthyroidism elevates p75NTR levels and its ligands, pro-nerve growth factor and pro-brain-derived neurotrophic factor, in rat liver. Further we showed that most of the apoptotic cells in hyperthyroid liver express p75NTR. We also demonstrated that triiodothyronine administration to rats causes NF-kappaB activation, but persistent exposure (10 days) to triiodothyronine deactivates NF-kappaB leading to sustained c-Jun N-terminal kinase (JNK) activation.

CONCLUSIONS

This study showed that hyperthyroidism-induced apoptosis in rat liver involves the activation of death receptor-mediated pathways, including p75NTR.

Molecular targets in cerebral ischemia for developing novel therapeutics

Cerebral ischemia (stroke) triggers a complex series of biochemical and molecular mechanisms that impairs the neurologic functions through breakdown of cellular integrity mediated by excitotoxic glutamatergic signalling, ionic imbalance, free-radical reactions, etc. These intricate processes lead to activation of signalling mechanisms involving calcium/calmodulin-dependent kinases (CaMKs) and mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK). The distribution of these transducers bring them in contact with appropriate molecular targets leading to altered gene expression, e.g. ERK and JNK mediated early gene induction, responsible for activation of cell survival/damaging mechanisms. Moreover, inflammatory reactions initiated at the neurovascular interface and alterations in the dynamic communication between the endothelial cells, astrocytes and neurons are thought to substantially contribute to the pathogenesis of the disease. The damaging mechanisms may proceed through rapid nonspecific cell lysis (necrosis) or by active form of cell demise (apoptosis or necroptosis), depending upon the severity and duration of the ischemic insult. A systematic understanding of these molecular mechanisms with prospect of modulating the chain of events leading to cellular survival/damage may help to generate the potential strategies for neuroprotection. This review briefly covers the current status on the molecular mechanisms of stroke pathophysiology with an endeavour to identify potential molecular targets such as targeting postsynaptic density-95 (PSD-95)/N-methyl-d-aspartate (NMDA) receptor interaction, certain key proteins involved in oxidative stress, CaMKs and MAPKs (ERK, p38 and JNK) signalling, inflammation (cytokines, adhesion molecules, etc.) and cell death pathways (caspases, Bcl-2 family proteins, poly (ADP-ribose) polymerase-1 (PARP-1), apoptosis-inducing factor (AIF), inhibitors of apoptosis proteins (IAPs), heat shock protein 70 (HSP70), receptor interacting protein (RIP), etc., besides targeting directly the genes itself. However, selecting promising targets from various signalling cascades, for drug discovery and development is very challenging, nevertheless such novel approaches may lead to the emergence of new avenues for therapeutic intervention in cerebral ischemia.

Energy metabolism during cutaneous wound healing in immunocompromised and aged rats

Cutaneous cells primarily depend upon carbohydrate metabolism for their energy requirement during healing process. But, it may be greatly hampered during various pathological and altered physiological conditions. The present study was therefore undertaken to investigate the intermediate steps of energy metabolism by measuring enzyme activities in the granulation tissues of immunocompromised and aged rats following excision-type of cutaneous injury. The activities of key regulatory enzymes hexokinase (HK), phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS) and glucose-6 phosphate dehydrogenase (G6PD) have been monitored in the wound tissues of immunocompromised and aged rats at different time intervals (2, 7, 14 and 21 days) of postwounding. The activities of HK and CS were found significantly decreased both in immunocompromised and aged rats as compared to control subjects. However G6PD exhibited an elevated activity at early stage followed by a decreased activity at later phase of healing both in immunocompromised and aged rats. The PFK and LDH demonstrated an upward trend in immunocompromised rats but a decreasing trend in aged rats. Thus, the results suggest that significant alterations in the activities of energy metabolizing enzymes in the granulation tissues in both immunocompromised as well as in aged rats may overall affect the energy availability for cellular activity needed for repair process. Hence, this may perhaps be one of the factor responsible for impaired healing in these subjects.