Trends in traffic accident mortality and social inequalities in Ecuador from 2011 to 2022.

BACKGROUND: Traffic accidents (TA) remain a significant global public health concern, impacting low-and middle-income countries. This study aimed to describe the trend in TA mortality and inequalities in Ecuador for 2011-2022, distributed by year, gender, age group, geographical location, type of accident, and social inequalities. METHODS: An ecological study was conducted using INEC national-level data on TA fatalities in Ecuador. Mortality rates were calculated per 100,000 population and analyzed by year, gender, age group, geographic region, and accident type. Annual percentage variation (APV) was determined using linear regression models. Inequality analyses examined associations between TA mortality and socioeconomic factors like per capita income and literacy rates. Complex measures such as the Slope Inequality Index (SII) were calculated to assess the magnitude of inequalities. RESULTS: There were 38,355 TA fatalities in Ecuador from 2011 to 2022, with an overall mortality rate of 19.4 per 100,000 inhabitants. The rate showed a non-significant decreasing trend (APV - 0.4%, p = 0.280). Males had significantly higher mortality rates than females (31.99 vs. 7.19 per 100,000), with the gender gap widening over time (APV 0.85%, p = 0.003). The Amazon region had the highest rate (24.4 per 100,000), followed by the Coast (20.4 per 100,000). Adults aged ≥ 60 years had the highest mortality (31.0 per 100,000), followed by those aged 25-40 years (28.6 per 100,000). The ≥ 60 age group showed the most significant rate decrease over time (APV - 2.25%, p < 0.001). Pedestrians were the most affected group after excluding unspecified accidents, with a notable decreasing trend (APV - 5.68%, p < 0.001). Motorcyclist fatalities showed an increasing trend, ranking third in TA-related deaths. Lower literacy rates and per capita income were associated with higher TA mortality risks. Inequality in TA mortality between provinces with the highest and lowest per capita income increased by 247.7% from 2011 to 2019, as measured by the SII. CONCLUSION: While overall TA mortality slightly decreased in Ecuador, significant disparities persist across demographic groups and geographic regions. Older adults, males, pedestrians, and economically disadvantaged populations face disproportionately higher risks. The increasing trend in motorcycle-related fatalities and widening socioeconomic inequalities are particularly concerning.

Protein tyrosine phosphatases regulate arachidonic acid release, StAR induction and steroidogenesis acting on a hormone-dependent arachidonic acid-preferring acyl-CoA synthetase.

The activation of the rate-limiting step in steroid biosynthesis, that is the transport of cholesterol into the mitochondria, is dependent on PKA-mediated events triggered by hormones like ACTH and LH. Two of such events are the protein tyrosine dephosphorylation mediated by protein tyrosine phosphatases (PTPs) and the release of arachidonic acid (AA) mediated by two enzymes, ACS4 (acyl-CoA synthetase 4) and Acot2 (mitochondrial thioesterase). ACTH and LH regulate the activity of PTPs and Acot2 and promote the induction of ACS4. Here we analyzed the involvement of PTPs on the expression of ACS4. We found that two PTP inhibitors, acting through different mechanisms, are both able to abrogate the hormonal effect on ACS4 induction. PTP inhibitors also reduce the effect of cAMP on steroidogenesis and on the level of StAR protein, which facilitates the access of cholesterol into the mitochondria. Moreover, our results indicate that exogenous AA is able to overcome the inhibition produced by PTP inhibitors on StAR protein level and steroidogenesis. Then, here we describe a link between PTP activity and AA release, since ACS4 induction is under the control of PTP activity, being a key event for AA release, StAR induction and steroidogenesis.

Silencing the expression of mitochondrial acyl-CoA thioesterase I and acyl-CoA synthetase 4 inhibits hormone-induced steroidogenesis.

Arachidonic acid and its lypoxygenated metabolites play a fundamental role in the hormonal regulation of steroidogenesis. Reduction in the expression of the mitochondrial acyl-CoA thioesterase (MTE-I) by antisense or small interfering RNA (siRNA) and of the arachidonic acid-preferring acyl-CoA synthetase (ACS4) by siRNA produced a marked reduction in steroid output of cAMP-stimulated Leydig cells. This effect was blunted by a permeable analog of cholesterol that bypasses the rate-limiting step in steroidogenesis, the transport of cholesterol from the outer to the inner mitochondrial membrane. The inhibition of steroidogenesis was overcome by addition of exogenous arachidonic acid, indicating that the enzymes are part of the mechanism responsible for arachidonic acid release involved in steroidogenesis. Knocking down the expression of MTE-I leads to a significant reduction in the expression of steroidogenic acute regulatory protein. This protein is induced by arachidonic acid and controls the rate-limiting step. Overexpression of MTE-I resulted in an increase in cAMP-induced steroidogenesis. In summary, our results demonstrate a critical role for ACS4 and MTE-I in the hormonal regulation of steroidogenesis as a new pathway of arachidonic acid release different from the classical phospholipase A2 cascade.

An arachidonic acid-preferring acyl-CoA synthetase is a hormone-dependent and obligatory protein in the signal transduction pathway of steroidogenic hormones.

We have described that, in adrenal and Leydig cells, the hormonal regulation of free arachidonic acid (AA) concentration is mediated by the concerted action of two enzymes: an acyl-CoA thioesterase (MTE-I or ARTISt) and an acyl-CoA synthetase (ACS4). In this study we analyzed the potential regulation of these proteins by hormonal action in steroidogenic cells. We demonstrated that ACS4 is rapidly induced by adrenocorticotropin (ACTH) and cAMP in Y1 adrenocortical cells. The hormone and its second messenger increased ACS4 protein levels in a time and concentration dependent way. Maximal concentration of ACTH (10 mIU/ml) produced a significant effect after 15 min of treatment and exerted the highest increase (3-fold) after 30 min. Moreover, (35)S-methionine incorporation showed that the increase in ACS4 protein levels is due to an increase in the de novo synthesis of the protein. On the contrary MTE-I protein levels in Y1 and MA-10 cells did not change after steroidogenic stimuli. In contrast with the effect observed on protein levels, stimulation of both cell lines did not change ACS4 RNA levels during the first hour of treatment, indicating that the effect of both stimuli is exerted at the level of ACS4 protein synthesis.StAR protein induction has a key role on the activation of steroidogenesis since this protein increases the rate of the limiting step of the whole process. In agreement with the fact that the inhibition of ACS4 activity by triacsin C blocks cAMP-stimulated progesterone production by MA-10 Leydig cells, here we demonstrated that ACS4 inhibition also reduces StAR protein levels. Moreover, exogenous AA was able to overcome the effect of triacsin C on both events, StAR induction and steroidogenesis. These results were confirmed by experiments using ACS4-targeted siRNA which result in a reduction in both ACS4 and StAR protein levels. The concomitant decrease in steroid production was overcome by the addition of AA to the knocked-out cells. In summary, this study suggests that in adrenal and Leydig cells the hormonal action prompts the synthesis of a labile protein, ACS4, which activity is involved in the regulation of AA release and is essential for steroidogenesis and StAR protein induction.

Tyrosine phosphates act on steroidogenesis through the activation of arachidonic acid release.

The ACTH signaling pathway includes both PKA activation as well as PKA-dependent tyrosine phosphatase activation. In addition, the action of this hormone also includes the regulation of the intracellular levels of arachidonic acid (AA) by the concerted action of two enzymes: an acylCoA-thioesterase and an acyl-CoA-synthetase (ACS4). This work describes the production and characterization of a specific ACS4 antibody, which was used to analyze the effect of ACTH on ACS4 protein level in Y1 adrenocortical cells and the putative relationship between tyrosine phosphatases and ACS4. The antiserum was obtained from rabbits immunized with the recombinant ACS4. This immunogen was produced in bacteria and eluted from an acrylamide gel after SDS-PAGE separation of a partially purified bacteria lysate. When used in Western blot analysis, the antibody obtained specifically recognized only one protein of the molecular mass corresponding to ACS4, in Y1 cells and in several rat tissues. Using the antibody described here, we analyzed the effect of ACTH stimulation on ACS4 protein level. The hormone produced an increase of this acyl-CoA synthetase in Y1 adrenocortical cells. Moreover, this effect was mimicked by cAMP and partially reduced by a tyrosine phosphatase inhibitor. We propose that ACTH regulates ACS4 protein levels through a PKA-dependent mechanism that could involve also PTP activity.