Current Molecular Pharmacology - Online First

Post-traumatic osteoarthritis (PTOA) constitutes a distinct subtype of osteoarthritis (OA). Despite extensive research, no effective pharmacological intervention has been established to prevent or halt the progression of PTOA. Current therapeutic approaches are primarily limited to symptomatic management and pain relief. SkQ1, a novel mitochondria-targeted antioxidant, has emerged as a promising therapeutic agent due to its dual capacity to scavenge excessive intracellular reactive oxygen species (ROS) and modulate inflammatory responses.

This study aimed to investigate the therapeutic potential of SkQ1 in the early stages of PTOA and elucidate its underlying molecular mechanisms.

Chondrocytes were cultured under varying concentrations of SkQ1 to evaluate its cytotoxicity. Additionally, an in vitro oxidative stress model was established to assess the antioxidant effects of SkQ1 across different concentration levels, from which the optimal concentration for PTOA treatment was determined. The rat PTOA model was established through medial meniscal tear (MMT) surgery, followed by intra-articular administration of SkQ1 postoperatively. The gait characteristics of rats in each group were assessed biweekly following surgery. Outcome measures were evaluated at 2 and 6 weeks postoperatively, including pathological evaluation of knee cartilage, ROS levels, markers of oxidative damage, such as malondialdehyde (MDA) and 8-hydroxy-deoxyguanosine (8-OHdG), mitochondrial membrane potential, mitochondrial DNA copy number, and apoptosis-related cytokines.

In vitro, lower concentrations of SkQ1 (500 nM) exhibited superior antioxidant efficacy while minimizing cytotoxicity. The results indicated that SkQ1 administration significantly enhanced knee joint functionality and mitigated articular cartilage degeneration in both the acute and subacute phases of PTOA by inhibiting oxidative stress pathways. In a rat model of PTOA, SkQ1 not only alleviated gait abnormalities, but also substantially reduced levels of oxidative stress biomarkers, including ROS, MDA, and 8-OHdG. Furthermore, SkQ1 effectively preserved mitochondrial membrane potential and increased mitochondrial DNA copy number. Mechanistically, SkQ1 inhibited the release of cytochrome C (Cyt-C) and apoptosis-inducing factor (AIF) and downregulated key components of the mitochondria-mediated apoptotic pathway, such as Bax, Bak, cleaved caspase-3, and cleaved caspase-9.

The findings suggested that SkQ1 exerts its therapeutic effects via multiple mechanisms, including the reduction of ROS accumulation, mitigation of oxidative damage, preservation of mitochondrial function, and inhibition of apoptotic pathways. These diverse actions position SkQ1 as a promising disease-modifying agent for PTOA treatment, potentially offering benefits that extend beyond those provided by current symptom-focused therapies.

Endometrial cancer is one of the most common gynecological malignancies. Endometrial cancer cells express the gonadotropin-releasing hormone (GnRH) and its receptor (GnRH-R). Among the various therapeutic approaches for the treatment of endometrial cancer is the use of GnRH conjugates, such as the AN-152, created by linking the [D-Lys⁶] GnRH with the cytotoxic doxorubicin through an ester bond. An undesirable property of these conjugates is their vulnerability to plasma carboxylesterases, which cleave the ester bond to release doxorubicin before reaching the cancer cells.

To overcome this problem, we recently developed the Con-3 and Con-7, which are GnRH analogs conjugated through a disulfide bond with the cytotoxic mitoxantrone. In this study, we determined the cytotoxic properties of the Con-3 and Con-7 on the Ishikawa endometrial cancer cells, assuming that their interaction with the GnRH-R of cells exposes the conjugated mitoxantrone to the cellular thioredoxin. The cellular thioredoxin reduces the disulfide bond of Con-3 & Con-7 to release mitoxantrone, which accumulates in the cancer cells and exerts its cytotoxic actions.

Indeed, treatment of Ishikawa cells with Con-3, Con-7, or the free unconjugated mitoxantrone increased their apoptosis and decreased their proliferation in a dose- and time-dependent manner, displaying half-maximal inhibitory concentrations (IC50) of 0.64 - 1.15 µM. In specific, the IC50 values on days 2, 3, and 4 were 1.45, 0.64, and 0.83 μΜ, respectively, for Con-3, 0.91, 0.82 μΜ, and 1.00 μΜ, respectively for Con-7 and 1.15, 0.98, 0.78 μM, respectively for mitoxantrone.

In contrast, the free, mitoxantrone-unconjugated peptides did not affect the proliferation of Ishikawa cells. The Con-3 and Con-7 could put the basis for the development of a new class of anticancer drugs for endometrial cancer, which will act as “prodrugs” that deliver the cytotoxic mitoxantrone in a GnRH-R-specific manner.

This work aimed to evaluate the anti-inflammatory and myorelaxant effect of thymol (TM) and carvacrol (CAR) in the pregnant rat uterus. Both compounds exhibit considerable antimicrobial, antispasmodic, and anti-inflammatory effects and due to these properties, they were studied in this in vitro model of premature birth induced by infection.

All uterine tissues were studied in uterine contraction tests to determine the inhibitory effect of TM, CAR (10, 56, 100, 150, and 230 µM), and nifedipine (a calcium channel antagonist) on phasic and tonic contraction induced by electro- and pharmacomechanical stimuli. The quantitative determination of cyclic adenosine monophosphate (cAMP) induced by TM and CAR in the uterine lysate was carried out by ELISA. For the determination of the anti-inflammatory effect of TM, the pro-inflammatory cytokine, interleukin (IL)-1β, in uterine samples stimulated with lipopolysaccharide (LPS) was measured. Forskolin (FSK) was used as a positive control to evaluate the cAMP and cytokine levels. TM, CAR, and nifedipine inhibited the uterine contractions at the highest concentration level, however, nifedipine was the most equipotent (p<0.05). In addition, TM and CAR did not increase the intracellular cAMP production in comparison with FSK (p<0.05). However, both compounds were able to decrease the LPS-induced production in a concentration-dependent manner that was considered statistically significant (p>0.05).

Finally, both the anti-inflammatory and uterine relaxing effects induced by TM and CAR were neither associated with the increase in cAMP levels nor with the production of IL-1β in pregnant rat uterine samples. Therefore, TM and CAR can be considered as alternative adjuvants for the treatment of infection-induced preterm labor. Before the in vitro experiments, an in-silico analysis was conducted using the Expaisy online server to evaluate the biological effects of thymol on uterine contraction.

It is crucial to know the interaction and identification of genes encoding the Voltage-dependent L-type calcium channel subunit alpha-1C proteins, because of the functional relationship it may have in the inhibition of the uterine contraction. These properties place TM as a potentially safe and effective adjuvant agent in cases of preterm birth, an area of pharmacological treatment that requires urgent improvement.