Mechanism of inhibition of the human immunodeficiency virus type 1 by the oxygen radical generating agent bleomycin

Challenges and future directions of potential natural products leads against 2019-nCoV outbreak

Except for Remdesivir® no other drug or vaccine has yet been approved to treat the coronavirus disease (COVID-19) caused by the virus known as, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Remdesivir® an small molecule and nucleic acid analogue, it is used to treat adults and children with laboratory confirmed COVID-19, only administrated in hospital settings. Small molecules and particularly natural products count for almost fifty percent of the commercially available drugs, several of them are marketed antiviral agents and those can be a potential agent to treat COVID-19 infections. This short review rationalized different key natural products with known activity against coronaviruses as potential leads against COVID-19.

Heme arginate potentiates latent HIV-1 reactivation while inhibiting the acute infection

Human immunodeficiency virus-1 (HIV-1) successfully escapes from host immune surveillance, vaccines and antiretroviral agents. The available antiretroviral compounds can only control viremia, but it is impossible to eliminate the virus from the organism, namely because HIV-1 provirus persists in the reservoir cells from which the virus repeatedly disseminates into new cells. Current therapeutic approaches, however, do not specifically address the stage of virus reactivation. Heme has been demonstrated as very efficient in inhibiting HIV-1 reverse transcription, while its derivative hemin ameliorated HIV-1 infection via induction of heme oxygenase-1. Normosang (heme arginate; HA) is a human hemin-containing compound used to treat acute porphyria. In this work, we studied the effects of HA in HIV-1-acutely infected T-cell lines, and in cell lines harboring either a complete HIV-1 provirus (ACH-2 cells) or an HIV-1 "mini-virus" (Jurkat clones expressing EGFP under control of HIV LTR). We demonstrate that HA inhibited HIV-1 replication during the acute infection, which was accompanied by the inhibition of reverse transcription. On the other hand, HA alone stimulated the reactivation of HIV-1 "mini-virus" and synergized with phorbol ester or TNF-α in the reactivation of HIV-1 provirus. The stimulatory effects of HA were inhibited by N-acetyl cysteine, suggesting an increased redox stress and activation of NF-κB. Further, HA induced expression of heme oxygenase-1 (HO-1) in ACH-2 cells, while HO-1 was found expressed in untreated Jurkat clones. Inhibitor of HO-1 activity, tin protoporphyrin IX, further increased HA-mediated reactivation of HIV-1 "mini-virus" in Jurkat clones, and this effect was also inhibited by N-acetyl cysteine. The stimulatory effects of HA on HIV-1 reactivation thus seem to involve HO-1 and generation of free radicals. Additionally, the effective concentrations of HA did neither affect normal T-cell activation with PMA nor induce activation of the unstimulated cells. In conclusion, HA appears to possess a combination of unique properties that could help to decrease the pool of latently infected reservoir cells, while simultaneously inhibiting HIV-1 replication in newly infected cells. Our results thus suggest a new direction to explore in treatment of HIV/AIDS disease.

Bleomycin has antiviral properties against drug-resistant HIV strains and sensitises virus to currently used antiviral agents

In this study we performed phenotypic assays to assess involvement of the cancer chemotherapeutic agent bleomycin (BLM) in replication inhibition of mutant HIV-1 viral strains. Three clinically relevant mutant HIV variants, including one containing the Q151M mutation conferring multinucleoside resistance, were equally as sensitive to BLM as the wild-type HXB2 strain. Long-term incubation of BLM with a wild-type HIV(Ba-L) strain did not alter the sensitivity of the strain to BLM (IC(50) of BLM 0.64 microM at the beginning of incubation to 0.58 microM). At the same point in time, resistance to lamivudine (3TC) and zidovudine (AZT) was noted. Interestingly, the BLM-treated virus showed hypersensitivity to both AZT and 3TC. Our results suggest a contribution of BLM in viral load reduction in patients receiving both anticancer and antiviral agents and harbouring both wild-type and resistant HIV strains.

Expression of a novel alternatively spliced UCP-2 transcript in osteogenic sarcoma

BACKGROUND

Development of chemoresistance is common in patients with osteogenic sarcoma (OGS); however, the underlying mechanism is largely unknown. Many anticancer drugs exert their therapeutic action by generating reactive oxygen radicals, which might be countered by the cancer cell through induction of uncoupling protein 2 (UCP-2). UCP-2 has been shown to be able to protect tumor cells from the cytotoxic actions of chemotherapeutic drugs. Because OGS is seldom completely cured by current chemotherapy regimens, we hypothesized that increased expression of UCP-2 underlies this phenomenon. The primary initial interest of our research was to evaluate the level of UCP-2 mRNA in OGS.

METHODS

The level of UCP-2 mRNA was determined by reverse transcriptase polymerase chain reaction (RT-PCR) comparing expression in normal-bone-derived specimens and OGS-derived specimens. Semiquantification of mRNA expression was achieved by radioactive RT-PCR. Nucleotide sequencing was performed using automated instruments.

RESULTS

Interestingly, we failed to observe induction of UCP-2 mRNA in OGS tumor specimens and OGS-derived primary cell lines compared to the expression level in normal bone. However, we found expression of a hitherto unknown UCP-2 transcript in eight of eight OGS-derived and one EWS-derived cell lines and in nine of ten OGS biopsy specimens but in only one of six normal bone-derived specimens. Thus, tumor samples express both types (normal and the novel one) of UCP-2 mRNAs, whereas normal bone expresses only the wild-type form. Further experiments identified the novel mRNA species as an alternatively spliced UCP-2 transcript (termed UCP-2as). UCP-2as has a 22-nucleotide insertion from the 3' end of intron 3 that introduces an early stop codon in exon 4, which theoretically can produce a protein 79 amino acids long.

CONCLUSIONS

We have identified a hitherto unknown UCP-2 transcript. Expression of the novel transcript appears to be OGS-specific, implying a function advantageous to the tumor.