4-Deoxyphorbol inhibits HIV-1 infection in synergism with antiretroviral drugs and reactivates viral reservoirs through PKC/MEK activation synergizing with vorinostat.

Latent HIV reservoirs are the main obstacle to eradicate HIV infection. One strategy proposes to eliminate these viral reservoirs by pharmacologically reactivating the latently infected T cells. We show here that a 4-deoxyphorbol ester derivative isolated from Euphorbia amygdaloides ssp. semiperfoliata, 4ß-dPE A, reactivates HIV-1 from latency and could potentially contribute to decrease the viral reservoir. 4ß-dPE A shows two effects in the HIV replication cycle, infection inhibition and HIV transactivation, similarly to other phorboids PKC agonists such PMA and prostratin and to other diterpene esters such SJ23B. Our data suggest 4ß-dPE A is non-tumorigenic, unlike the related compound PMA. As the compounds are highly similar, the lack of tumorigenicity by 4ß-dPE A could be due to the lack of a long side lipophilic chain that is present in PMA. 4ß-dPE activates HIV transcription at nanomolar concentrations, lower than the concentration needed by other latency reversing agents (LRAs) such as prostratin and similar to bryostatin. PKCθ/MEK activation is required for the transcriptional activity, and thus, anti-latency activity of 4ß-dPE A. However, CD4, CXCR4 and CCR5 receptors down-regulation effect seems to be independent of PCK/MEK, suggesting the existence of at least two different targets for 4ß-dPE A. Furthermore, NF-κb transcription factor is involved in 4ß-dPE HIV reactivation, as previously shown for other PKCs agonists. We also studied the effects of 4ß-dPE A in combination with other LRAs. When 4ß-dPE A was combined with another PKC agonists such as prostratin an antagonic effect was achieved, while, when combined with an HDAC inhibitor such as vorinostat, a strong synergistic effect was obtained. Interestingly, the latency reversing effect of the combination was synergistically diminishing the EC50 value but also increasing the efficacy showed by the drugs alone. In addition, combinations of 4ß-dPE A with antiretroviral drugs as CCR5 antagonist, NRTIs, NNRTIs and PIs, showed a consistent synergistic effect, suggesting that the combination would not interefer with antiretroviral therapy (ART). Finally, 4ß-dPE A induced latent HIV reactivation in CD4 + T cells of infected patients under ART at similar levels than the tumorigenic phorbol derivative PMA, showing a clear reactivation effect. In summary, we describe here the mechanism of action of a new potent deoxyphorbol derivative as a latency reversing agent candidate to decrease the size of HIV reservoirs.

Toxic hepatitis induced by a herbal medicine: Tinospora crispa.

Herbal remedies are becoming increasingly popular in many countries. Tinospora species (Menispermaceae) is commonly used as a herbal medicine in South Asia, but very few toxic effects have been described. We report a case of acute hepatitis associated with chronic use of high doses of Tinospora crispa. A 49-year-old male with chronic low back pain bought a herbal medicine at a market in Vietnam that was supposed to be Tinospora crispa, and started to take 10 pellets per day. He had no medical history and did not take any other drugs or toxins. Four weeks later; he developed dark urine and pale stools, associated with asthenia and right hypochondrial pain. Two months after starting treatment, he was referred to the hepatology department with jaundice. Blood tests showed aspartate aminotransferase: 1.169 IU/l, alanine aminotransferase: 2.029 IU/l, total bilirubin: 20.47 mg/dl, direct bilirubin: 13.29 mg/dl, and γ-glutamyltransferase: 243 IU/l. Viral and autoimmune hepatitis were eliminated. Upper abdominal ultrasound was normal. Histopathological findings were consistent with a toxic reaction. The herbal medicine was stopped on admission and the patient fully recovered without treatment, with normal liver function 2 months after the acute episode. Tinospora crispa was clearly identified in the pellets by microscopic analysis of the botanical characters combined with chromatographic fingerprints. The use of herbal medicines containing Tinospora crispa can induce toxic hepatitis. Recovery can be complete after discontinuation. This case highlights the risk associated with traditional herbal remedies.

Biological potential and structure-activity relationships of most recently developed vascular disrupting agents: an overview of new derivatives of natural combretastatin a-4.

Tumor blood vessels are an important emerging target for anti-cancer therapy. The antimitotic agent combretastatin A-4 (CA-4), a cis-stilbene natural product isolated from the South African tree Combretum caffrum Kuntze, is the lead compound of a new class of anti-cancer drugs that target tumor vasculature. CA-4 inhibits tubulin polymerization by interacting at the colchicine binding site on tubulin. This alters the morphology of endothelial cells and causes vascular shutdown and regression of tumor vasculature. Some tubulin-binding vascular-disrupting agents (VDAs) are currently in clinical trials for cancer therapy. As a consequence of the potential favorable applications of these compounds, several analogs projected to induce rapid and selective vascular shutdown in tumors have been synthesized during the last few years. Many of these molecules have already been tested for their effects on tubulin polymerization as well as for their antiproliferative activity and other biological properties, and possible mechanisms of action have been investigated. The aim of the present review is to offer an overview of most recently developed combretastatin derivatives, focusing on biological effects exerted by these compounds. The published data about new analogs are presented and compared, and a detailed investigation of structure-activity relationships is described.

Efficient conversion of aucubin into 6-epi-aucubin

Selective deprotection of peracetylaucubin (3) by use of KCN led to 6-O-acetylaucubin (4), which was readily converted into 2',3',4',6', 10-penta-O-benzoylaucubin (7). Configuration inversion performed on 7, using a modified Mitsunobu reaction, followed by deprotection, afforded 6-epi-aucubin (2).